Saturday, March 29, 2008

Tattletale Lichens

Lichens are both beautiful and good. They indicate healthy air.

Last month when I was helping some friend assess their trees they were worried about the lichens “eating away” at their fruit trees’ wood. Assuming they were parasitic, he had used a wire brush to remove all the lichens from one tree. It jogged my memory.

Such trees are covered with a wonderful patina of various colors and shapes of lichens. The lichens take so many fascinating forms: circles of warm orange, furry gray-brown wavy circular fans, wavy greenish-brown circles, and the many other curious forms.

My friends were worried that a horrible fungus has invaded the trees’ living tissues. Fortunately, lichens are not parasitic. They live on the outer bark without effecting the living cells. (A lichen is an odd combination of both fungal filaments algae cells, usually a green algae.)

In 1866, William Nylander, a Finnish naturalist, was the first to link the disappearance of lichens and air pollution. He noticed that some lichen species present within Luxembourg Gardens, Paris, were missing in other parts of the city. He attributed these differences to air quality. Over the next thirty years, fumes from coal-burning industrial furnaces gradually led to the eradication of the lichen population within the park.

Sulfur dioxide (SO2), the result of industrial and urban emissions, does the most widespread damage to lower plants, even though it is only one of several air pollution components in the atmosphere.

Why are lichens sensitive to air pollution? Since lichens lack roots, surface absorption of rainfall is the only means of obtaining vital nutrients which are dissolved in rainwater. Lichens act like sponges, taking in everything that is dissolved in the rainwater, and retaining it. Since there is no means of purging the SO2, the sulfur content accumulates within the lichen and reaches a level where it breaks down the chlorophyll molecules which are responsible for photosynthesis in the algae. When the photosynthetic process stops in the algae, the algae die and this leads to the death of the fungus.

Since it is known that different species of lichens vary in sensitivity to air pollution, scientists can use these organisms as monitors of air pollution and as indicators of air quality. This is very useful because modern air quality instruments cannot measure the effects air pollution has on living cells and they are limited to measuring present conditions.

Most importantly, the lack of lichens on fruit trees would be a sure indicator that their orchard is not free from the harsh chemical sprays that harm and kill lichens.

I could readily tell that the air quality was fine in their backyard just by looking at what is growing on the bark of older trees. Take some time and look at the bark of some of your older trees. Hopefully, a few scattered patches of gray or orange lichens can be seen growing on the bark. Near a city, there is an obvious change in what is growing on tree trunks. Here there are areas where lichens don’t exist, such areas are termed "lichen deserts". As the air quality in these lichens deserts improve, lichens will begin to reappear in a slow process of recovery.

Lichens are sensitive to air pollution and have disappeared from many metropolitan and industrial areas over the last century. Lichens’ sensitivity to pollutants are actually used as biomonitors—like a green version of a canary in the coal mine.. Lichens are valuable research tools and through the information they provide, we can have a better understanding of the impact air pollution has on the environment.

There many books on the subject. Here are two:

T.H. Nash (Ed.). Lichen biology. Cambridge University, Press, 1996. Pp. 303
ISBN 0 521 45368 2

"This book is in the tradition of the work of ME Hale 'The biology of lichens', the third edition of which appeared in 1983 (first published in 1967). It provides a comprehensive and up-to-date account of the fascinating world of lichens. The last chapter explains the role of lichens as indicators of air pollution and the pollutant effects on lichen biology is discussed."

Another book with less jargon is: By D. H. S. Richardson, Paperback; Naturalist's Handbook Series: 19. Pollution monitoring with lichens. Published by Richmond Publishing Company, 1992, ISBN 978- 0855462895

To see more detail of the illustration(s) put you cursor over the image and double click.

All rights reserved. Copyright 2008

Visit my web site to learn about my gardening books.

Note: I seem to have lost the usual way to leave comments. To do so, either click on the "___ comments" button or click on the title of the blog under "Blog Archive". Thanks, Robert

Friday, March 28, 2008

Lavender, Part 1

A Lavender for All Reasons
My renewed love affair (see my first post) with lavender (
Lavandula spp.) began during the California drought of 1977 as a matter of necessity. As the planting portion of my business shriveled from lack of water, I began looking for drought-hardy plants to work with. The drought, by taking its toll on established landscapes, slowly revealed, like a grim version of time-lapse photography, which plants could best take the neglect and still look reasonably attractive— and lavenders were one of the champions. Lavandula spp., has become a love of mine and one of the three most important plants in my landscape design "palette". (The other two are rosemary and santolina.)

Planted correctly in my garden, lavenders can easily be sustained with irrigation during an entire rainless California summer. I plant as the fall rains begin and the roots thrive all winter long. Not only does this produce lush growth the following spring, but I have needed no irrigation there after. (I live in the cool coastal climate with a 30-year average rainfall of 58’—USDA Zone 10a) If you have the right plant in the correct place, you may be able to achieve an irrigation-free garden. But you will have to experiment, even in places where there is summer rain. And especially in the arid Southwest.)

I use larger, shrubby lavenders act as effective weed suppressants since their two- to four-foot-tall canopy shades out most germinating seeds. Equally important, lavenders require very limited shearing to maintain a pleasant and attractive form. All of this saves on my garden’s maintenance.

With lavenders, I constantly remind myself of the "three D"s——drainage, drainage, drainage. The chaparral (a xerophytic—dry—plant community common to Mediterranean climates) of Greece and California can share a common characteristic——rocky soil. In Greece, the best-looking plants were those that seemed to flourish miraculously out of the rocky, nutrient-poor crevices of sheer mountain cliffs. (Also, the only place the goats and sheep couldn't get to the plants!) The beautiful form of cliff-dwelling chaparral plants is a testament to the plant's tolerance, if not preference, for rocky soil with extreme drainage. While a typical rocky Greek "soil" (a flattering word for the decomposed and crumbled remnants of rocky cliffs and outcroppings) is low in many nutrients, especially the often-overrated nitrogen, it is high in two important factors: minerals and drainage, both absolutely essential to lavenders.

The high mineral content of rocky soil may also be a preference, if not a necessity, for lavenders and other Mediterranean herbs. Cy Hyde, of Well Sweep Herbs, suggests "the sand we use to plant a lavender and mound up around the base of the plant to encourage drainage may actually be good for it in other ways. Art Tucker (of the Horticulture Department of Delaware College) has some research to show that the sand in the soil increases the volatile-oil content of the herb's foliage." Thus, rocky, mineral, sandy, or gravelly soil amendments seem to provide more than one benefit.

The clay so often present in many home landscapes I’ve worked in is deadly to lavender; while the clay may be high in total nutrients, its moisture-holding capacity works against the needs of lavender roots. These roots, especially the upper four to ten inches—the crown of the root system, are very prone to crown rot (Phytophthora spp.) and various root rots, fungal diseases, stem mildews, and blights.

Contrary to regular garden practice, I always amend my small planting mounds for lavenders with the addition of plenty of gravel. Drainage is so critical to lavenders that, in any form of a clay loam, the addition of gravel, sand, or a similar non-nitrogen amendment for drainage is absolutely essential. When in doubt about the drainage of a particular garden soil, amend raised planting mounds or plant in a container filled with a well-drained potting mix. The single most important lesson when gardening in my Mediterranean ecosystem is that providing the essential drainage is not only critical, but, makes for better plant growth and, at the same time, the watering needs are not increased , they may actually be reduced.

Lavandiferous Canopies for Weed Control
With a landscape plan, I usually choose a lavender by its size and form first, then for color of leaf and flower. I usually place larger lavenders at the back of the design, further from prominent pathways, so as to have a mounding, spherical form that also shades out weeds trying to sneak in from the garden perimeter. For this application, my three favorites are
L. dentata (sold in the west as French lavender), Sweet lavender (which I've mostly purchased as L. heterophylla ), and Spike lavender (this one is usually sold as L. latifolia, sometimes as L. spica ). All have a wonderfully rounded, half-spherical form and grow, not including blossom stems, from 2.5 to 4 feet high, depending upon the soil.

Of the three,
L. dentata has the longest and most frequent periods of bloom—all months of the year, except for a few weeks during late summer/early winter and, occasionally, in the early spring or mid summer. The L. dentata blossom is a delightful pastel tone of lavender; too subtle for some tastes, but I prefer pastels more than hot colors. The foliage is a soft, fuzzy grey-green color and the leaves are, in the words of Hortus Third, "linear-oblong, crenately toothed to pectinate-pinnatifid, obtuse, revolute, sessile". I think of the leaves as soft gray with rounded, large saw-toothed edges.

Spike lavender,
L. latifolia, has a very narrow flower on a long, somewhat-branched stem. The blossom color is also subtle and, because of the smallness of the bloom, the flowers aren't very noticeable. A bonus, however, is the long, fine stem of the dead flower heads which lasts for a long time as a vertical line in the landscape, and doesn't look too tacky. If I never get around to shearing the spike lavender, the deadheads are a nice addition to a natural-looking garden—since nature doesn't bother to shear her Grecian lavenders (except by means of browsing goats!).

When it comes to the sweetest, most delicate lavender debate, I throw my Greek fisherman's hat into the
L. angustifolia and its many cultivars. My special L. angustifolias’s include: The pure white ‘Alba compacta’, ‘Richard Gray’, the extraordinary long color of ‘Baby’s Blue’, ‘Hidcote’, ‘Munstead’, the wonderful pink-flowering ‘Miss Katherine’.

For sheer drama and rich color of blossom, my vote goes to
L. stoechas, sold as Spanish lavender around here. In the linguistic gymnastics of Hortus Third , the flowers are "oblong-obovate, to 2 in. long, verticilasters 6-10 -fld., calyx to .25 in. long, 13-nerved, corolla dark purple." What excites me is the spectacularly-rich, royal purple "flags" that stand straight up from the top of the flower. The beauty of Spanish lavender has inspired me to spend considerable time reviving my long-lost love of super-close-up floral photography in an attempt to capture the naked, abstract "essence" of the blossom. My favorite named-variety for these floral "nude studies" is L. stoechas 'Atlas'. This one has by far the tallest, most regal "flags". A close contender for bud size is L. stoechas 'Otto Quest', which is much more prevalent in the average wholesale and retail nurseries around here. The species (unnamed selections or seed-grown plants) form of the Spanish lavender has dramatically smaller blossoms, only up to 5/8ths of an inch compared to the 3/4-to-one-inch-long buds of 'Otto Quest' and the nearly 1.5 inch buds of 'Atlas'. The advantage to the species form is its well-behaved plant-shape and reduced shearing demands. And again, remember that those plants selected for huge blossoms flop over easier and can't take overhead irrigation or rain.

There is a strikingly odd form of lavender in my garden—-a lime-green/yellow-flowered form of Spanish lavender (
L. stoechas ‘Viridis’)-see the photo above. This plant's foliage is also noticeably more yellow than some green-leaved lavenders, making it hard to work with when designing a landscape, because of the difficulty of blending its color in with most other colors. (The lime-yellow blossoms do make an excellent foil or counter-balance to the royal purple of the 'Atlas' blossoms when I do micro-photography.) This plant with a robust, resinous, and “primitive” foliage is the L. stoechas 'Viridis' I favor for grilling. See the following recipe. (More about lavenders later as my Lavandins begin to bloom. These are crosses between L. latifolia (L. spica) and L. angustifolia.)

Chicken "Pressada" with Lavender

"Pressada" is my Americanized, corrupted Italian way of saying the chicken is pressed between two layers of herbs. This is based on a dish I had while traveling south of Naples, Italy—except the Italians used thyme. This recipe cooks chicken very quickly and makes for an intense lavender flavor throughout the meat because the oils of the lavender “steam” the chicken. I like this recipe because it’s more theatrical than any other barbecue I know and it’s a conversation piece. This is a true gardener’s recipe because one could never afford to buy the amount of herbs this recipe calls for at a culinarily-enriched supermarket or fancy farmer’s market. This is a recipe for edible landscapers.

One barbecue pit or grill.
A medium-sized bag of briquettes.
Fire starter paper, wooden kindling and matches.
A 10- by 20-inch cast iron pancake griddle.
A cookie sheet as big or bigger than the griddle.
Five to 10 bricks.
Two pair of long barbecue tongs.
Cooking oil (olive oil works fine) and a natural-hair pastry brush.
A serving platter with garnish.

6 to 8 boneless chicken breasts, or other boneless cuts.
A five-gallon bucket loosely filled with lavender foliage and flower stalks.

Start the charcoal:
Start enough charcoal briquettes to form a layer one or two briquettes thick beneath the entire surface of your griddle. Start the briquettes in a can with an open top and bottom and some holes punched around the bottom. Use newspaper and kindling to start the fire so the petrol taste of lighter fluid is eliminated.

Harvest the lavender while the coals are heating the griddle. Trim more foliage than flowers, as the leaf adds more flavor. Use this as a chance to trim back the plant to a more compact form. Woody stems are not a problem, but younger, more succulent growth will release more fragrance.

Once the flames are out and the briquettes are glowing white at the edges, rearrange in a layer beneath the griddle. When the coals get the griddle nearly orange hot, where a splattering of oil dances and sizzles on the grill, you're ready to begin.

Cooking the Chicken
Quickly coat the griddle with the olive oil. This is to keep the herbs from sticking and to make it easier to clean the griddle. Don't use a brush with plastic bristles as the intensely-heated griddle will melt the bristles.

Quickly layer up to two-inches of lavender prunings on the griddle with the stems running the length of the griddle. Be sure to cover the griddle thoroughly with the lavender, leave no holes.

In a rapid fashion, lay the boneless chicken breasts across the top of the lavender—perpendicular to the lengths of lavender.

Now, quickly cover the chicken with another two-inches of continuous lavender foliage. Put the cookie sheet on top of the chicken-and-lavender. Then stack the bricks to press the lavender and chicken into a compressed "sandwich" —the “pressada” part.

Because the heat supercharges the volatile oils in the lavender, the steam and oil mixture quickly cooks the chicken like a pressurized sauna. The chicken may only need five- to 10-minutes per side, if the griddle was nearly orange hot. Or, it may take 15- to 20-minutes per side if the charcoal wasn’t hot enough.

After the proper time (which you’ll learn in short order by practicing), quickly: remove the bricks and the cookie sheet and use the tongs to quickly turn the "sandwich" over. The lavender and chicken usually holds together enough to make a unified whole. You'll either amaze your friends or have to quietly reassemble the lavender-and-chicken sandwich while eating humble pie. Practice make perfect.

After the proper length of time on the second side, remove the bricks and cookie sheet. Remove the top layer of the lavender, lift the chicken off the bottom layer of foliage and place on a platter.

Remove the lavender and the griddle from the grill. Quickly restoke the coals to a good-and-hot temperature and place the chicken breasts on the grill diagonal to the metal's line. Brown briefly. Turn the chicken to create a brown cross-hatching. Grill a cross-hatching on the other side.

Serve the browned chicken on a rice pilaf or on top of bed of colorful mesclun (Spring mix) salad greens.

While eating, you can add leftover lavender foliage to the coals throughout the evening to produce a hazy romantic atmosphere infused with a heady smoky-lavender fragrance. Or, use the leftover lavender to smoke on the grill other fish and meats for the coming week’s lunches. Grill pork chops, turkey drumsticks, turkey breasts, salmon, hot dogs (don’t waste these on the kids), tuna, or sausages.

All rights reserved. Copyright 2008

To see more detail of the illustration(s) put you cursor over the image and double click.

Visit my web site to learn about my gardening books.

Note: I seem to have lost the usual way to leave comments. To do so, either click on the "___ comments" button or click on the title of the blog under "Blog Archive". Thanks, Robert

Thursday, March 27, 2008

Raised Beds-It's Spring!

Raised beds in the garden, not the bedroom.

The simplest and most inexpensive way to make raised vegetable beds is to cultivate and rake soil up into a mounded shape. This type of “bed” should in no way be considered a raised bed made by the cultivation method often referred to as the French intensive-biodynamic raised bed. See John Jeavons classic—How to Grow More Vegetables: Than You Ever Thought Possible on Less Land Than You Can Imagine. The methods outlined by Jeavons produces a proper mound of slightly-raised soil and offers the best way to improve the tilth and fertility of your soil.

Many gardeners, however, prefer to construct formal raised beds framed within masonry, plastic, or wooden sides. These sides retain the soil while imparting order and efficiency to the kitchen garden and helping to define it. Formal raised beds also provide a number of other advantages:

 Enhanced drainage for better growth.
 Soil which warms slightly sooner in the spring.
 Sides which help keep soil or mulch from spilling into paths.
 A structure which allows wire mesh to be added to the bottom of a bed to exclude tunneling pests such as moles, gophers, and hedgehogs. However, It’s obvious that carrots prefer a deep soil (as shown to the left) with good tilth and drainage, free of rocks and obstructions that can produce deformities. In less than ideal soils, cultivate as deeply as possible before seeding. Carrots are best grown in double-dug beds with vigilant trapping of gophers, or in boxes raised 24 inches above the soil line and constructed with wire bottoms to deter gophers or other underground gnawing pests. (The root system of a carrot is taken from my new book Roots Demystified, Change Your Gardening Habits to Help Roots Thrive. The grid is one-foot square.) This shows that in a deep soil carrots are able to grow nearly eight feet deep and five feet wide!. This means that even a 24-inch raised be leaves plenty of roots for vegetarian gophers to feast on. This illustrates why extra water and nutrients are needed to satisfy a normally vast root system. (Click on the image to get a clear, detailed view of the illustration as it appears in the book.)

When building garden boxes, line the bottoms with one-half-inch aviary wire, which comes in four-foot-wide rolls. One-inch chicken wire, while less expensive, may allow baby gophers to sneak inside the box. The aviary wire also has more galvanized metal and lasts longer in the ground. Even with this protective barrier in place, the taproot and many other roots will be eaten at the bottom edge of the wire.

 The Cadillac version is to use one-quarter-inch hardware cloth because it doesn’t rust through as quickly.
 When preparing beds for planting, be sure to work the soil with a spading fork to crack open the soil before building the box. After the soil is in, use a flat-bottomed spade so you don’t damage the wire.
 A way that pathways between beds can be cleaned and tended without disturbing plantings.

Raised beds also have certain limitations or drawbacks:

 A formal raised bed with solid sides will cost more and require more time and effort to construct than a simple mounded bed.
 Some gardeners find the angular geometry of the raised-bed structures unaesthetic. (Beds can, however, be masked by perennial plantings or low evergreen hedges.)
 When watering a raised bed with drip irrigation, extra effort must be made to bring the water supply into the bed unobtrusively.

There are many materials which can be used to construct a raised bed. Each has its own unique mixture of attributes and imperfections:

Used Bricks (Recycled)
 Very good looking; construction has character when first built.
 Since bricks are fairly narrow, the finished wall doesn’t take up excess garden space.
 Wire mesh is easily added to the bottom.
 Uses recycled materials.

 Expensive if new.
 Requires some masonry skill or practice to construct.
 In areas where the ground freezes, requires a poured concrete base.

Cinder Blocks

 Wide enough to sit on while gardening.
 If unmortared, easier to work with than brick.
 Can be built on a base of packed gravel
 Easy to add wire-mesh bottom .

 Not easily found as recycled material.
 Best used only for square and rectangular beds.
 Thick blocks take up garden space
 Looks gray and “industrial,” like concrete.
 The large holes in the blocks, usually placed facing up, tend to fill with mulch and soil from the bed.
 Unless mortar and a concrete base are used, the blocks will often settle in a slightly skewed position.

Plastic “Wood”
 Easy to work with, like lumber. No splinters.
 Made from recycled consumer plastic waste.
 Has a long life and won’t rot.
 Easy to add a wire-mesh bottom.
 Easier construction of odd-angled shapes such as octagons or pentagons.

 Up close, looks very fake.
 Expensive compared to lumber.
 Requires screws instead of nails for sturdy attachment.

Recycled, Untreated Rot-Resistant Lumber

The use of the two main rot-resistant lumbers available, redwood and cedar, is controversial due to environmental issues. They are, however, still the easiest material for building raised beds. (Use of recycled wood lessens environmental impact.)

 Good-looking natural surface.
 Available as recycled material.
 Easy to work with; no mask, gloves, or goggles required when using hand tools.
 Easy to add wire-mesh bottom.
 Can be used to construct odd-angled shapes.

 If in contact with the soil, may have to be replaced within 4-20 years. (Note: redwood heartwood can last this long, but white redwood sapwood usually rots within four years and should be avoided.)

So, the choice is yours. Happy gardening.

Please leave a comment- I'd like to hear from you.

To see more detail of the illustration(s) put you cursor over the image and double click.

All rights reserved. Copyright 2008

NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert

Visit my web site to learn more about my gardening books.

Wednesday, March 26, 2008

Deer versus Predators

When it gets down to it, deer are beautiful, graceful animals. They can leap a four-foot cattle fence with a elegant and simple leap. Before I wax eloquent, I notice the deer are now sampling even the Euphorbias in my garden. How can they stand the bad-tasting, poisonous sap? Hopefully it was just a sampling and they discovered it’s not a plant for even the most distraught of times.

Until this year, does were dropping two fawns each year. Now they are sometimes giving birth to only a single fawn. I wonder what is going on.

In years past, natural predators—bobcats and mountain lions—helped balance the deer herd, perhaps preventing excessive population explosions. With the encroachment of human habitat and agricultural endeavors on the forest and wilderness (sheep in my “backyard”), the role of predators in moderating or regulating deer populations has been greatly diminished or eliminated. Unfortunately, the predators of deer often don't mix well with suburbia or livestock. The predators of deer require large areas for their territory and are often quite shy of human activity. Furthermore, agricultural activities such as dairy and sheep herds and poultry flocks fear such predators and the farmer usually attempts to exterminate these wild cats.

I know one rural resident who was upset when a bobcat killed some of the chickens in his tiny, ram-shackle coop. But he was even more distraught when he couldn't get a clear shot at this pesty intruder. For the sake of a few eggs which were the last symbols of his back-to-the-land lifestyle—his vegetable garden had long ago been decimated by deer leaping the short, inadequate fence. This self-proclaimed environmentalist was willing to kill one of the only remaining natural predators of deer. This was the same environmentalist; who was, at the time, promoting ocean wave generation of electricity as the non-polluting answer to our coastal energy needs. He was willing to kill the first bobcat to reappear in the area in years for the sake of a little symbolic cholesterol-in-a-shell. This example clearly shows how environmental issues can so easily be segmented into seemingly unrelated fragments. A better chicken coop, a proper deer fence and a little tolerance or reverence for the sleek, marvelously-patterned bobcat could begin to strike a more normal balance with respect to deer and bobcat alike.

Ah, there is now a grape vineyard where the sheep used to graze. The vineyard manager has a “predation permit” to shoot deer that happen to get through the eight-foot fence that surrounds the 30 acres of grapes. Now the predators of deer are slowly beginning to return. I spot bobcats, or their scat, at least four times a year. I was woken up from a nap by a cacophony of many species of birds. I knew this meant they were trying to drive a bobcat away. I raised my head to see, not a bobcat, but a young mountain lion (cougar) slowly walking four feet from my house a casually through the garden. Being on the second floor, he didn’t even know I existed. The main predator of deer was back after 20 years of no sightings. I can often tell when he returns because I find the scat on the driveway and the deer don’t walk past my office every day as they used to like clockwork. I found the skeleton of a mature buck on the hillside next to the creek. Only a mountain lion is big enough to take down a mature five-point buck.

Until the return of the mountain lion, and still unto this day, the deer have had to fear another predator—the mechanical hunter called the automobile? On many a dark night, on a lonely country or suburban road, the metal meets the flesh. Sometimes the car wins and in the morning buzzards find a tasty meal. Sometimes the car looses and a radiator is pushed into the engine block and the local repair shop makes a killing—and the deer usually suffers a fatal blow. Occasionally, the car's occupants take some of the impact.

An individual deer is just small statistical blip in the population he or she belongs to. If said deer happens to be munching on your favorite rose buds, then all this highfalutin talk about the return of predators may seem like a waste of time. Your pissed at that *#^&$#@ deer, and he's got to go! Right. You can shoot what seems to be all the deer in the area, and they can recover to be a problem in a relatively short period of time. Even if you can tolerate the sight of a 150 pound mountain lion prowling around your kid's sandbox, predators most likely won't be able to keep the deer population low enough to solve many urban and suburban deer problems. One deer may not make a population in the eyes of a naturalist, but it's big enough to make a mess out of my much-beloved apple trees.

Please post a comment - I want to know what you think.

All rights reserved. Copyright 2008

To see more detail of the illustration(s) put you cursor over the image and double click.

Visit my web site to learn about my gardening books.

NOTE: I have lost the usual way to leave a comment. Try clicking on “__ comments” below or click on the title of the blog under “Blog Archive”. I’m still trying to fix the problem. Thanks

Tuesday, March 25, 2008

The Fungus Among Us

(Here's a portion of the chapter called "The Fungus Among Us" on mycorrhizal association from my most recent book Roots Demystified, Change Your Gardening Habits to Help Roots Thrive.)

According to experts on the subject, the intriguing life-forms known as fungi comprise about 52% to 55% of a forest’s biomass. Since a whopping 80% of all green plants depend on at least one fungal relationship in order to survive, it’s appropriate here to discuss the magical relationship of beneficial fungi with the roots of trees as well as with a range of annual, herbaceous, and woody plants. This relationship is known as mycorrhiza, or fungus root, from the Greek: mykes [mushroom] and rhiza [root]. The plural is mycorrhizae.

Fungi, in general, form masses of tiny filaments known as mycelia, which frequently interact with plant roots. There are two major kinds of mycorrhizae: ectomycorrhiza and endomycorrhiza. In ectomycorrhiza (usually abbreviated as “EM”), these filaments remain outside of the plant, living on the cells of the root hairs. With endomycorrhiza, these filaments actually live between and inside of the cells of the feeding roots. There are numerous kinds of tongue-twisting endomycorrhizae: arbutoid, monotropoid, ericoid, orchidioid, and vesicular-arbuscular or arbuscular mycorrhiza, all of which interact with plants in different ways. The most important and widely distributed type of mycorrhiza is the vesicular-arbuscular mycorrhiza or arbuscular mycorrhiza (abbreviated as “VAM” or “AM”.) These are the new terms for endomycorrhiza. (Some plants utilize neither EM nor VAM; examples of plants with no mycorrhizal association include all the species of brassicas—cabbage, broccoli, cauliflower, Brussels sprouts, etc.)

All mycorrhizal associations are beneficial and are characterized by the movement of plant-produced carbon to the fungi and fungal-acquired nutrients to the plant. Rather than a parasitic relationship, it is a mutualism in which both life-forms benefit. In general, most plants are dependent upon this union, as it is estimated that about 80% of all plant species in the world are mycorrhizal symbionts.

In general, mycorrhizal plants are well-fitted to endure environmental stress. Nutrient-poor or moisture-deficient soils show improved capacity for supporting plant growth and reproduction when mycorrhizal fungi are present. As if to return the favor, the plant allows the mycorrhizal fungi to extract sugars, starches, proteins, and lipids from its lateral roots. (We’ll go into more detail a few paragraphs down.) Mycorrhizal fungi may also improve water absorption, increase drought resistance, and exude substances that reduce infections caused by some soil pathogens.

Phosphorus is the most common nutrient transferred via VAM association into the root system of a plant, especially if it is growing in soil that is low in this essential nutrient. All trees need phosphorus but are not always able to absorb soluble phosphorus efficiently; they are thus dependent upon the mycorrhizal relationship. The mycorrhizal fungi produce phosphatase enzymes that breakdown phosphorus compounds. (The absorption of micronutrients such as zinc and copper is also improved by mycorrhizal association.) The extensive mass of a fungal mycelium produces a huge surface area that allows the fungi to “mine” a much greater amount of soil and duff than the root hairs of the tree are capable of exploiting on their own.

As an example, the mycorrhizae can increase the absorbing surface area of pine seedlings by 80%. Some horticulturists maintain that the absorption surface area of a tree can be increased by 700-1000% by mycorrhizal fungi. Fortunately, there are plenty of these helpful organisms to go around. One scientist in Europe documented 101 species of mycorrhiza fungi associated with a single tree species—Norway spruce (Picea abies)—and 117 mycorrhizal species associated with Scotch Pine (Pinus sylvestris).

See the photo of Redwood seedlings with (right) and without (left) mycorrhizae. Photo credit: Mike Amaranthus, USDA

The B&W illustration is from Roots Demystified. It shows to two types of mycorrhizae-EM (on the right) and the VAM (on the left).

Please post a comment- I'd like to know what you think.

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Gopher it!

It's spring, the young gophers are out, searching and fighting over new territory. The battle begins.

The earliest “modern” settlers of our coast north of the San Francisco bay were the Russians in March of 1812. They were gone by 1842. One anecdotal saying goes “we could have made a living if it weren’t for the ground rats”.

Ah yes, the hated gopher. These herbivores tunnel at both shallow and deep depths to eat on the roots of plants. An average of 22 gophers per acre translates into four pounds of fresh vegetation eaten every day—a rather healthy diet. It is thought that there are 1,000,000,000 rodents in California of which the most abundant is the pocket gopher. Large fur-lined external cheek pouches are used for temporally storing food. Thus the name pocket gopher, referring to these pouches, or pockets. Sometimes they collect pieces of roots, such a carrots, and stash them in a food reserve burrow for perhaps a truly “rainy day”. Many gardeners have watched a wiggling garlic top or freshly-planted lettuce and all of the sudden it is pulled beneath the soil. Fodder for the ravenous western pocket gopher.
(Those of you who live in the northeastern part of the country are blessed—no gophers. Skip the rest with delight.)

Gophers are very nocturnal creatures walking or skirmishing across the surface looking for new places to burrow. This is especially frantic in the spring, usually March and April, as young gophers go for their own territory. Once a gopher has a territory it maintains if for life. But for unexplained reasons, male gophers are polygamous which means their territories overlap or they wander at night to court their next “babe”.

The common gopher snake is thought of by gardeners as a hopeful controller of this pest. Alas, studies have shown that only 6.4% of the snake’s diet comes from gophers—better than nothing I guess. (Gopher snakes are territorial. So don’t try to move one form someplace to your garden. They’ll just wander off in pursuit of their previous home.) Rattlesnakes get only 2.5% of their diet from eating pocket gophers as the tunnel system makes it unlikely for them to coil and strike. The most significant predator, at 71.4% of it’s diet, is the barn owl which eats at night as the rodents scurry along the surface of the soil. The average barn owl will eat 155 gophers per year. Alas, if a great-horned owl lives within one square mile, the barn owls are scared away or eaten—something overlooked by the local vineyards that are trying to appear to be environmentally responsive by putting up barn owl nesting boxes near where great-horned owls reside.

In spite of the barn owls, most gardeners have resorted to wooden raised beds with wire bottoms—galvanized one-half inch aviary wire or hardware cloth. This doesn’t always stop them. A friend has vegetable boxes 12 inches high with wire bottoms. There was a gopher mound or “throw”, such as they are inclined to make when surfacing, up against the wood. He watched as the gopher merely climbed on top of the throw and hopped over the top of the board.

Wire baskets are becoming required planting additions for perennials, shrubs and trees. I once had a wire basket protecting an apple tree. The wire was four inches above the mulch. That didn’t stop a gopher from climbing over the wire to be encaged with all those succulent roots. The tree leaned over and simply died. However, wire baskets often work.

Lining the garden with a fence is trickier and riskier. Studies show that the fence would have to be at least two feet deep and up to seven feet deep in deep soils. One research study found gophers getting over a 10-inch high barrier! One recommendation would be that the fence would have to extend to 12 inches above the soil. Nothing is simple or safe!

I recently helped maintain an estate garden riddled with gophers. Even though all the dahlias were wrapped in 1/2” aviary wire, up to one quarter were destroyed by these troublesome varmits. I taught another guy on the crew how to use a Macabee trap—with its piercing tongs. After a month or so he had killed 100 gophers. So I presented him with a Macabee trap sprayed gold as a trophy. Sad truth was the owner stopped the trapping program. Gopher mounds showed up in her lawn and more dahlias bit the dust.

There is no silver bullet.

I must admit I find gophers fascinating, when I’m not cursing them, knowing that they must tunnel to keep their teeth in order. If unable to tunnel, their teeth would grow up to 14 inches a year in a curl that would eventually pierce their skull. Not a pretty sight. Although many gardeners would be delighted.

I’m always curious about their tunnel systems. The feeding tunnels, which terminate in a mound, are usually four too eight inches beneath the surface. The maintain “highways” used for routine travel are 12 or more inches deep. And gopher tunnels have been found at a depth of six feet. So I tried pouring plaster of Paris down a tunnel. I did get some of the plaster down to the second run. This mold of a gopher run hung from my ceiling for months.

After St. Helens, in Washington, erupted in 1980 it was the activity of gophers, their defecation, that brought mutually-symbiotic mycorrhizae to inoculate other plants for a better and healthier life and the restoration of the disturbed soil. (Mycorrhizae are beneficial fungi that extend to the root system of many plants to make it easier to gather nutrients such as phosphorous. Trees are especially dependent on phosphorous for good growth. Without the mutual symbiosis of the mychorrhizal association most trees would not prosper. The tree gives the mycorrhizae carbohydrates in exchange—this is not a parasitic association but is a two-way street for the benefit of both.)

Gophers turn over the soil more effectively than earthworms. And the mounds are good for the soil. One report (Effects of Pocket Gopher Mounds on Plant Production in Shortgrass Prairie Ecosystems, W. E. Grant, N. R. French and L. J. Folse, Jr.) states “…total above-ground plant production would be increased by roughly 5.5% by the presence of the mounds.” So they aren’t completely malicious critters with no worth what-so-ever.

I still hunt these “ground rats”.

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Random Chaos (As opposed to formal chaos?)

I like to let my annual and biennial plants wander around in the garden. (The photo shows lime-green Euphorbias -E. characias - and foxgloves - Digitalis purperea. All from seed cast asunder by leaving the flower stalks to mature.)

Nature conceals the pattern of the placement of plants. Each hopeful seedling, each successful mature tree; grows in a haphazard pattern. If we want a truly natural look garden and feel to our constructed garden, we must avoid human constructs. Even attempts at gentle chaos often reveal a noticeable intent. True randomness means letting go.

Here’s a test for planting in a truly random fashion: Take five or more golf balls and throw them up onto the air over the area you want to plant. Where each ball falls is where you plant. The real task is not to move any balls—”oh that one looks so close to that ball”. Untouched balls can mean some very odd combinations—just like the forest or meadow.

We usually buy a plant, look in a book to see how far apart it should be planted, and plant with loving care. The difficulty with the random-balls approach is some patterns require buying more plants than you anticipated. Because several balls are clustered together, the gardener may feel the cost of extra plants is a burden. A forest of meadow has no expense account. Plants sprout, die, and thrive—all at the same time. Thousands of seedlings or plants have died to give birth to the one glorious specimen we appreciate. Such a pattern is within the natural flow of the random sprouting and growth of all natural things. Rejoice in the spontaneity.

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All rights reserved. Copyright 2008

The Pill "Bug" Debate

I’ve only—bless my lucky stars—found one garden snail in three years. I plucked it yesterday off the base of a sculpture in my garden that was awash with eight-inch tall, moist miner’s lettuce. Where was he hiding all the past years? Where are the rest of them? I bet he can’t be a bachelor. (This is the snail that escaped from an “escargot farm” after being introduced to California in the 1800s—not the rarely-seen native snail.)

But the sow bugs and pill bugs are now out in full force this spring.

Consider the lowly sow bug (they don’t curl up and have two tiny tails) or the cute pill bug pictured above, also called rollie-pollies—actually Isopods, the only land crustacean related to the lofty crab and lobster. These innocent little critters are beginning, once again with the advent of spring, to be falsely accused in the gardeners’ court-of-law. All kinds of people ask me how to kill, with safe methods, these "nasty bugs who are devouring everything in my garden”. I have to gently tell them that these particular critters may have been falsely incriminated by circumstantial evidence. If Perry Mason were still alive to represent these small, helpless creature in a gardener's court of law, they may be exonerated.

Although one gardener friend saw a pill bug eat a flower bud of a pansy. And a friend says, in greenhouses and young seedlings in flats where it can be very moist, pill bugs may be so abundant that they damage young plants. I asked Richard Merrill (my organic gardening “guru” with over 25 years of teaching organic gardening) about this and he responded “isopods prefer decaying organic matter... or rather more accurately they prefer the microbes of decay on the organic material. If they are without water and exposed to new seedlings, isopods will eat them also, but this is rather rare.”

So maybe it’s not beyond a shadow of a doubt.

Some commercial chemical compounds used by the uninformed to “eradicate” pill and sow bugs contain diazinon, a very toxic poison that is rated as equally toxic as the infamous DDT, And, according to the Rachael Carson Trust, is a suspected teratogen (causing birth defects in the next generation).

Pill bugs are part of nature's important decomposing cycle. That is, these “bugs” are usually eating mostly on moist rotten, decayed, dead, and decomposing plant tissues. Some other creatures, such as the nasty Mr. Slug, Mr. Snail, or Mr. Earwig, do the initial damage to the plant and the unsuspecting and opportunistic pill bug comes in to take advantage of the very first bits of rot, is falsely accused—and thus, is innocently killed.

Take strawberries as a wonderful example. As gardeners, we might awaken in the morning to find a pill bug neatly rolled up within a cavity so neatly carved within the largest, most gorgeous strawberry in the garden. If we were to actually reconstruct the "crime", what probably occurred was that herd of tiny slugs mounted a midnight raid of the berry patch, chewing tiny caverns in each berry. The very first tiny bits of oxidized-rot and decay sent (actually, scent) out a signal to the pill bugs that a new taste-treat of succulent decay was available. The pill bugs climb into these "condominiums" of repast and proceed to feast away. The sun slowly rises as the slimy villains, the slinky slugs, slither back into dark, dank hiding places, places that are not where they just got done feasting. The pill bugs, with carefree abandon, colonize the holes formally carved by other pests. The gardener finds the pill bug at the scene of the crime and inflicts a form of instant, shameless justice. Again Richard Merrill, “I have tried in vain to see isopods eat strawberries. I have seen slugs eat them (nocturnally) and then when the isopods become active, they seek out the holes in the berries for water.”

The "solution" I try to take, is not to try to eradicate sow and pill bugs. But I’m fortunate that I can mulch my perennials with turkey manure mixed with rice hulls and still allude these troublesome critters.

To reduce the populations of pill and sow bugs around her raised boxes of vegetables (as well a slugs, earwigs, and “escargot”) a friend maintains bare soil with no mulch and very little organic matter or fiber on its surface for four feet or more in all directions.

Plant only the most healthy and vigorous transplants (the pill bugs eat on the very first tiny bits of rotten tissue when a seedling has minute amounts of damage from mildew, rust, and damping-off) into warm, dry, and bare garden soil. Then flood flats and pots in a bucket of water to flush out pill bugs.

I think because my ornamental garden is never irrigated in the summer; I don’t have many slugs, snails (except the "Lone Ranger"), or earwigs. Lucky me!

But there are the pill bugs eating mulch and the decaying weeds I’ve pulled up.

Please comment – I’d like to know what you think.

Note: I seem to have lost the normal way to enter a comment. To do so, click on the "___ Comment Button below. Or, click on the title of the post under "Blog Archive".

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Monday, March 24, 2008

A SOD Story, attachment to "my" forest.

Not the loss of lawns, which I can easily get over. But Sudden Oak Death syndrome (SOD).

SOD is decimating “my” forest. This alien disease first appeared in Marin county—the county just south of me—in 1995, although some say it may have been here since the mid ‘80s. It is caused by the water mold disease called Phytophthora ramorum.

The devastation of the tan oak along this ridge is enormous. As I drive home, the last three miles of the forest reveal hundreds of small and large dead and dying trees—some as high as 30 feet. It looks like a botanical firebombing. The dead trees stand out because they don’t loose their dead leaves for years, if not a decade or more. These sentinels are possibly a harbinger of things to come. SOD is decimating “my” forest. 

(A list of potential native host plants is at the end of this blog.)

Already the California bay laurel on this property is looking pretty shaggy and there is die-back on some of the limbs. Tan oaks and California bay tress make up 80% of the trees surrounding my house. Some say “this may merely be one of nature’s ‘house cleanings,’ removing genetically weak or damaged trees and leaving the healthier, stronger ones to produce better, sturdier offspring.” Well, I’m looking at a dead 40-foot high by 50 wide dead tan oak tree just 40 feet from my office and it’s not a pretty picture. I keep telling myself it wouldn’t be so bad if the leaves would fall off so the tree doesn’t look so miserable. But I still resent the death of these trees. These trees may follow the way of the elms that once graced so many yards and streets and the chestnuts that once were the major forest tree in the Eastern woodlands. But I hate it when it’s happening in my forest.

There will be a cascading effect on plants and animals as these trees die in greater numbers. As an example, the acorn woodpecker makes good use of the nuts from this tree. Squirrels nest in it. More than 300 species of animals; including 170 species of birds, 80 or more mammals and 60 varieties of amphibians and reptiles, and more than 5,000 insects make a home out of the habitats provided by the coastal live oak and tan oak trees, according to Bill Tietje, a natural resources specialist with the University of California Cooperative Extension. An acre of oak woodlands can have 10 to 100 million individual invertebrates which help to digest the decomposing oak parts to recycle nutrients for new growth. In the words of John Muir, “When we try to pick out anything by itself, we find it hitched to everything else in the universe.”

The death of tan oaks has been a great struggle at learning how to be unattached to the flow of nature (and mankind for that matter.) Sometimes as I drive home I simply gaze in a way that seems to selectively block out the view of the brown-leaved ghosts of the oak. I use to return from a trip out of state or the country and wonder in amazement at why I went somewhere else when it’s so beautiful here. Now when I return, I’m shocked at the death in the forest that I’ve forgotten about when I traveled. The forest may not cry, but I do. 

The ecological changes that happen will be slow and I probably won’t see the recovery or replacement of this wonderful tree in my lifetime. So the tragedy seems so personal. I am only one piece of the ecology but a very selfish one that doesn’t want to witness the slow demise or partial downfall of this tree that was here long before me. I just can’t let go.

This is the list of those trees and plants known to be host plants for the disease in California.

Scientific Name Common Name(s)
N= Native, MH = Grows around my house.

Acer macrophyllum Bigleaf maple - N
Adiantum aleuticum Western maidenhair fern - N
Adiantum jordanii California maidenhair fern - N
Aesculus californica California buckeye - N, MH
Arbutus menziesii Madrone - N, MH
Arctostaphylos manzanita Manzanita - N. MH
Rhamnus californica California coffeeberry - N
Heteromeles arbutifolia Toyon - N
Lithocarpus densiflorus Tanoak – N, MH
Lonicera hispidula California honeysuckle – N, MH
Pseudotsuga menziesii var.
menziesii & all nursery
grown P. menziesii Douglas fir - N, MH
Quercus agrifolia Coast live oak - N, MH
Quercus chrysolepis Canyon live oak - N
Quercus kelloggii California black oak - N
Quercus parvula var. shrevei
& all nursery grown Q. parvula Shreve’s oak - N
Sequoia sempervirens Coast redwood - N, MH
Trientalis latifolia Western starflower - N
Umbellularia californica CA bay laurel, Oregon myrtle – N, MH
Vaccinium ovatum Evergreen huckleberry - N, MH

Please post a comment - I want to know what you think.

Note: I somehow lost the usual section "Post a comment". To leave a comment, simply click on the area/button that says "___ Comments". Clicking on the title of a Post under "Blog Archive" also gets you to a view that gives the option of leaving a comment. I hope to figure this out soon. Robert

Visit my web site to learn about my gardening books.