Green Manures, free nitrogen

It's almost too late plant fava beans, a legume, in the fall. The soil needs to be somewhat warm. This may work in gardens in sunny gardens in the west and south-west gardens. Alfalfa works the best with corn, but this is just for planning next years spring garden. Leave room in your plans to grow some green manures. I'm using another fava bean flower as it's the only one I have without scanning a slide, which I'm to tired to do this morning. :=)

Legumes have gotten a lot of attention because of their ability to fix, via symbiotic bacteria that colonize the plant's roots, atmospheric nitrogen gas into available, "free" fertilizer. Because gardeners are preoccupied with the amounts of nitrogen in their soil, they are often fixated on legumes as a green manure. While legumes are important in a green manure mix, they are not a panacea. And a myth, or lack of understanding, about how this nitrogen fixation really works has confused gardeners and reduced their chances to maximize the nitrogen cycle.

The common perception that growing beans and corn together will help fertilize the growing corn plants is incorrect. Nitrogen-fixing plants, in temperate climates, didn't evolve to directly share the accumulated nitrogen with other plants. The ability to fix free nitrogen "out-of-thin-air", in the bacterial nodules on the roots, is a competitive, evolutionary development. This allows leguminous plants to colonize nutrient-poor soils. Legumes are some of the first plants to inhabit disturbed soils such as landslides, cliffs, beaches, sand dunes, and fire-scorched soil. When you think about it, the compacted clay subsoil that's left after most houses are built is really a disturbed soil. The legumes use all the nitrogen they accumulate to grow and make high-nitrogen seed. While the plant is growing, the nitrogen from the nodules on its roots is temporarily "banked", or stored, in the stems and leaves of the plant. This provides plenty of nitrogen for rapid assimilation into the blossom once seed begins to form. Consequently, the green bean plant growing up a corn stalk isn't about to share its nitrogen with the corn, during the current growing season. The mature beans contain 70 to 90 percent of the entire plant's total nitrogen. After the bean drop is harvested, the roots and their nodules have as little as three to six percent of the plant's total nitrogen--not much of a legacy, or fertilizer portfolio for the "heirs". So, to harvest a bean crop and till under the dry tops of the plant means you'd be getting only a very tiny amount of nitrogen back into the soil because the seed has most of the nitrogen, little nitrogen is left in the stems, roots, and leaves, and the tops are too carbonaceous for easy decomposition. (See illustration on pg. 265 of my "Edible Landscape" book.)

During the growth of a legume, very limited amounts of root nodule nitrogen can become available when the stress of grazing, mowing, drought, or death causes some of the nodules to wither, die, and rot in the soil. This is why the old way of grazing animals on pastures of mixed grasses and legumes works so well. When the cow grazes the pasture, some of the nodules on the legume's roots "shed"--they don't really jump anywhere, they just decompose--the grasses are able to quickly absorb the freed-up nitrogen for their growth. This makes for more pasturage, which entices the cows to eat some more. Meanwhile, the nitrogen-rich legume plants and bulky grasses makes for a goodly amount of nitrogen to be recycled via the bovine posterior--with deposits called meadow muffins, pasture patties, or cow chips.

"Free" Nitrogen with Good Timing

The optimal time to till under a green manure crop for maximum nitrogen (for a subsequent crop) is just before the blooms appear. The conscientious green manurer, must "sacrifice" beautiful blossoms for the optimal amount of nitrogen. I was visiting Ros Creasy one year when almost one third of her front yard had Crimson clover in full, glorious bloom. I timidly mentioned that the best effect for nitrogen occurs prior to bloom, or up to 20 percent of bloom. "Yes," she replied, "I won't get as much nitrogen, but look how absolutely gorgeous the bloom is! I don't mind giving up a bit of the nitrogen for the floral display. Besides, Crimson clover has a decent amount of nitrogen to spare and my soil isn't in horrible shape." Yep.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Hey, What About Those Hay Bales?

Growing annual vegetables on hay bales is a way to rapidly add lots of compostable organic matter to the soil’s surface in a short period of time. Here’s the recipe (See illustration from Designing & Maintaining Your Edible Landscape - Naturally) based on my trial garden in 1977!

· Place four or more bales of hay (which has lots of fresh, green nutrients) or straw (with more carbon than green nutrients) in a cluster. Place the bales on their sides, with the end grain facing up, and leave the strings on them.

· Thoroughly soak the cluster of bales..

· Add an three-thick layer of fresh manure to the top (in this case, the exposed end grain) of the bales.

· Add four or more inches of soil to cap off the top of the bales. (All right, I know this requires some digging. But it’s only a one-time effort to start of a remarkable process.)

· Water all the layers again.

· Plant potatoes with plenty of loose straw on top—six inches or more.

· Keep the potatoes and bales moist.

Et voilá! The bales will grow potatoes above the ground where no gophers can get to them.

After one seasonof planting and harvest, the bales will have rotted down quite a bit. (See the photo.) Plant them with bush beans, fava beans, other types of beans or potatoes again.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

My Virgin Kiwi Fruits

I usually cut my kiwi vines back very hard to allow for their cascade of foliage to keep my house cooler during the summer and the Indian summers. This year I was rushing to finish the revised edition of Drip Irrigation, for Every Landscape & All Climates, so the vines didn't get pruned. I've had flowers before, but this year one of the two vines brought forth dozens of flowers. Now I have dozens of fruit even though the male vine did not bloom. This is called "parthenogenesis". Fruit produced without any male fertilization. Explain that to me! Will wonders never cease. If it's like the last time this happened ten years ago, the fruits won't ripen until March! (Here the vines are cascading down two stories and out 15 feet.)

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Collodial Phosphorus, Cool or Not So Cool?

(The view looking down on one corn plant. The top six inches of roots.

Each square is one-foot square. Applies to the previous blog)

Purplish strips at the edges of corn leaves usually indicates a deficiency in phosphorus. Some organic gardeners use colloidal phosphate as the solution to this deficiency, but consider this: colloidal phosphate is often strip-mined in Florida, washed with water (and Florida has a big problem with supplies of fresh water), loaded on train cars, and shipped to places as far away as California and Washington, where it’s sacked up and shipped to your local garden-supply store.

[As a side note: Florida mines 75 percent of the phosphorous used by American farmers and about 25 percent of the entire world production. Phosphate ore must be chemically processed with sulfuric acid. When sulfuric acid reacts with the phosphate it produces a slightly radioactive byproduct known as phosphogypsum. According to the Florida Department of Environmental Protection, there are a billion tons of phosphogypsum stacked across the state and 30 million tons are generated each year.]

And the total amount of phosphorus (P₂O₅) in the sack is only 16 percent of all the bagged-up bulk, of which a mere two percent is available the first gardening season since the phosphorus is locked up in a mineralized form that requires the activity of soil microbes, soil bacteria, and exudates. (Exudates come from the roots and aid in the nutrient-release process by releasing; sugars, organic acids, and other compounds to dissolve minerals into a soluble state and stimulate the soil’s microbial action.) Unnecessary water use, exploitation of limited resources and wasted energy—all wrapped in a single bag. Add to this the fact that there is a limited supply of easily mined colloidal phosphorus. It’s much like oil: will we have enough in the future? Will we be able to find enough new supplies if the current mines are exhausted? Some say the U.S. supply will be gone by 2035. The world supply make be depleted in 50-100 years.

Choosing to buy commercial colloidal phosphate really means making a very important environmental decision. This is especially clear when one compares the environmental cost of imported amendments to the energy-efficiency of “growing” phosphorus at home by planting legumes and tilling the young foliage into the soil. Thus the gardener has two choices: (1) import nutrients, organic or not, to force an intensive yield, or (2) use wider spacing when planting and/or rotate heavy-feeder crops with a season of legumes to cut down on the competition for available nutrients. Whichever you choose, don’t grow corn in the same spot every year, as it will exhaust much of the nitrogen. Instead, alternate corn crops with green manures—that also increase available phosphorus.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Let's Get Real About Sustainability in Gardens

Consider corn as a way to look at true sustainability. Corn plants produce a massive root system that consumes large amounts of moisture and nutrients. The root system forms quickly: by the time a corn plant has formed just eight leaves it has produced 15 to 23 main roots with a total of 8,000 to 10,000 lateral roots. A mature plant can generate roots that have “ramified” (grown through) as much as 180 cubic feet of soil. (As seen in my book Roots Demystified, 2009.)

Corn plants need lots of nitrogen, and leguminous plants, as long as they’re not too crowded can provide it with all the nitrogen required. In a “natural” garden, the ultimate goal would be to eliminate almost all imported nutrients and other “inputs”. Horse manure, cow manure, sacks of bone meal, blood meal, green sand, bat guano, phosphates, or many other options—all add additional fertility, can qualify as “natural,” but come with various environmental costs attached; such as mining, transportation, energy use, and wasted bulk.

As an example of the energy invested in nitrogen for corn, consider blood meal. According to the Food and Agriculture Organization’s regulations, blood is introduced into the (processing) tank as a coagulated mass, previously obtained by a steam-action process. Ideally, as much liquid as possible should be squeezed from the coagulum. Heating is initiated at 82°C (180°F) and progressively raised to 94°C (200°F) for about three hours, then elevated to 100°C (212°F) for 7 hours. (That’s a LOT of energy). Drying is complete when the final moisture level in the dried product is about 12 percent.

Choosing blood meal at the nursery or organic supplier really means making a very important environmental decision compared to “growing” nitrogen at home by planting legumes and tilling the young foliage into the soil.

No matter what your source of imported nitrogen, whether for soil preparation or as a summer application for growth. It’s most effective to spread it relatively far from the cornstalk itself in order to feed the massive width of the corn root system most efficiently. One method of doing this would be to fertilize between the rows rather than on the rows themselves or at the base of each plant. If you plant intensively, be sure to add plenty of nutrients for this hungry crop.

Thus the gardener has three choices: import nutrients for intensive yields, or use a wider spacing and/or, rotate your crops to cut down on the competition for available nutrients. Don’t grow corn in the same spot every year, as it will exhaust much of the nitrogen. Instead, alternate it with green manures—legumes like fava beans (the flowers pictured above) tilled into the soil to provide nitrogen from the atmosphere. A good green manure should be tilled in before too much blooming.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Lessons From "Our" Droughts

As winter approaches, gardeners in the west now have three things on their minds—water, water, and water. Or, rather, the lack of it. The pale, arid shadow of a dusty drought now extends over much of the American west and southwest.

The drought, which has settled into much of the west over the past three years, doesn't make much noise. You can't hear the sound of the mud drying in the bottoms of empty reservoirs. You don't hear any noise from the leaves as they turn brown and fall off the trees in mid-summer. And you can't hear anything coming from the countless wells which have run dry.

The first drought for me, after moving to California, was the so-called Big Drought of 1975-1977. Our current drought, which has lingered for three long, parched years, has had its impact on wild lands, suburbs, and cities. Now, I get to improve my skills with gray water systems, drip irrigation, and xeriscape (drought resistant) planting techniques.

My first experiments with gray water systems—collecting water from sinks, showers, and laundries to irrigate fruit trees and ornamental landscaping—were during the 1970's drought. The systems I installed in the basements and crawl-spaces of clients throughout Marin county in those days were, in retrospect, a rag-tag, baling-wire collection of bizarre-looking gizmos. Now I’ve learned a lot more. See the photo on the left of a system designed with current “technology”.

In my experience, gray water is not a crisis-intervention scheme, but one of the many "tools" which allows my garden to flourish. The overwhelming feedback, and my personal experience, has been: "My plants are growing better with gray water than with any other water source."

I knew nothing about drip irrigation until the drought of the 70's. Again, the "Big" drought introduced me to a new gardening tool which has become commonplace in the 1990's. The technological advances in drip irrigation since I first started messin' with drip irrigation in 1975 have practically exceeded that of the revolution in the computer industry.

After experimenting with countless drip irrigation widgets and gadgets I've settled on my favorite emitter technology—in-line emitters. (As described in my updated edition of Drip Irrigation, For Every Landscape and All Climates. 2009) Unlike the more common punched-in emitter, which you buy separately and insert into a hole you've punched into solid drip irrigation tubing, in-line emitters come pre-fabricated inside the one-half inch drip irrigation hosing. On the right, see the interior of several emitters that become encased in ½-inch tubing. There is also a clear piece of tubing to reveal the emitter. All the real tubing is black or brown. Old-fashioned, punched-in emitters get brittle in the heat and sunlight and easily snap off during routine garden maintenance—which leads to tedious hours of repair. In-line emitters have nothing exposed to break off, are securely housed inside a sturdy one-half inch plastic tubing that'll take to abuse of weeding, gardening, and mulching, and are far less time-consuming since the emitters are preinstalled. With in-line emitters, I avoid the so-called "spaghetti" tubing which seems to somehow mysteriously move and knot itself and ends up resembling its namesake, a heap of tangled noodles.

The drought of the 1990's taught me how to plant so as to practically eliminate the need for drip irrigation. I've come to discover many ornamental Mediterranean plants are actually more drought-resistant than a lot of California native plants. There are small 18-year-old test plantings around my house which were planted at the beginning of our fall rainy season, and never irrigated again.

The first drought for me was the so-called Big Drought of 1975-1977. (By the way, how can a reduced amount of rain, be "bigger"? How can you have more of less?) Anyway, there have been plenty of "bigger" and longer droughts over the past 400 years. Tree ring analysis in the central portion of Santa Barbara county, the Santa Ynez Valley, indicates two periods of 60 years of drought (below "average" rainfall) since the 1500s

So, watch out, don’t count on a break in the drought.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

"Natural" Gardens?

Their really is no such thing as a natural gardener-made landscape. All gardens are constructs made by people, not by nature. Our gardens ultimately serve our needs, our sense of aesthetics. This means every gardener is really servicing their own ego. Our gardens do look nice, but they don’t really look natural. A natural garden would look as if nobody planted it or tends it. Therefore, a truly natural landscape would not satisfy most gardener's egos. If nobody recognizes the yard as the product of another person, nobody gets any compliments. A purely natural landscape would look so naturalized that most people would just walk by without noticing. The ultimate goal of an ego-free landscape designer or gardener would be a garden which no one identifies as manmade. But I've never met such a gardener.

Our gardens will always be a constant dialogue about the following terms: natural-like, naturalized, earth-friendly, sustainable (the latest buzz word), or environmentally-sound. Unnatural doesn't mean malevolent. We can have reasonably natural-like gardens that meet every definition of beautiful. Such landscapes are nice and unnatural.

Given that we are growing artificial gardens, exactly how natural-like can we get? More environmentally responsive than we may think. But the answers are in the details. Here's some pointers:

Gardeners usually try to do too much. Some yards have plenty of natural landscape to begin with. The typical approach is to remove almost everything that's there, buy a bunch of topsoil and plants and put completely new stuff back. Far from natural. And costly.

Don't even think of planting until you've fully realized the potential of what nature already provided. All that's often required is to selectively thin, prune or remove. The idea is to sculpt your existing plants to reveal their hidden form and texture. It's like Michelangelo carving away bits of stone to reveal the magnificence of the David.

Carefully trim limbs from a tree to reveal a serpentine or wonderfully-textured trunk(s). Or, shape existing native shrubs to reflect the line of a nearby tree or a distant hillock. Pull out weedy exotic shrubs to display the curve of a tree trunk, the rugged shape of an immense boulder or the multiple trunks of a large shapely shrub. Weed out exotic grasses to leave behind a scattered pattern of native grasses.

Or, as photographed here, carefully open up an odd-shaped hole in a tree's canopy to provide a slice of the distant horizon, a nearby lake or the silvery ocean. This is a garden in Big Sur, CA that is simply composed of trimming the upper limbs of a native coast oak (Quercus agrifolia) and a planted, but carefully placed Ceanothus spp. (known as tick brush or wild lilac, NO relation to the popular common lilac – Syringa vulgaris). This section of the garden is the closest to a constructed, native landscape I’ve seen.

Let me know what you think.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Mounds #2

Here's a drawing about mounds and swales I found. It might help with building the mounds I referred to in the previous blog. It may be too small. Try double clicking on the image for a slightly bigger view. I think I could post it on my web site in a bigger format if you like. Let me know. (It's from my first book - Designing & Maintaining Your Edible Landscape - Naturally)

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Mounds, not the candy

I like to plant trees and shrubs on constructed
soil mounds as opposed to planting them in
flat ground. If you’re working with slightly
heavy clay/loam soils, the mounding is
especially critical to preventing root or crown
rot (Phytophthora spp.—a fungal disease of the
upper portion of the roots, near the soil surface).
Many ornamental and fruiting tree and shrubs die
of crown rot without the gardener ever suspecting
the culprit. The fungus damages the sapwood,
either killing individual limbs or the entire plant.
Once the symptoms (pale-yellow, wilted leaves)
appear, it’s too late to do anything about it.

So, mounds help stave off root rot.

In areas where the summers are dry, make your
planting mounds in the fall; then all you have
to do in early spring after bare root roses, fruiting
and ornamental trees, and berries arrive is open
the winter wet soil enough to place the roots and
cover it with native soil. In areas where it rains in
the summer, wait until the soil drains after a rain
so that it’s moist, not wet.

Here you can see the cross section of a mound made
of composting chips and leaves from a tree service.
The mound is capped with six to ten inches of soil and immediately
planted. All plants are still planted on small mounds on the composting mound.

Based on my book Roots Demystified.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

The Dutch Win

This is the last landscape I installed before moving to the Farallones Institute Rural Institute to run the Edible Landscape Program. I inherited the plans from a student of the Harvard School of Landscape Design. He specified a herbal lawn mix between the redwood rounds. I didn’t approve of the redwood rounds for the patio as I knew there was too much white sap wood for them to last very long. Nonetheless, I followed the plan. I had already seen the “herbal lawn mix” at a public display garden. I knew one section was always blocked off due to too much usage, spilled sodas (maybe), and unknown spillages and urines.

The mix was composed of: creeping thyme (Thymus serpyllum), dwarf yarrow (Achillea millefolium), Roman chamomile (Chamaemelum nobile, usually listed in catalogs as Anthemis nobilis), and Dutch white clover (Trifolium repens).

I dutifully planted the mixture between the rounds. A year later, only the Dutch white clover remained. It is an aggressive plant. When grown as walkways between vegetable beds as a nitrogen source, it requires constant attention to control its spread.

Luckily the clients have no children as clovers leave nasty stains and are very attractive to bees.

Yet, it did provide a nice green mosaic between the rounds.

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Error in Paris

Last year I traveled to Paris. In one of the oldest parks in Paris was one of the oldest Sycamore trees in the city. This sign shows that all that history and current science has got it wrong about root growth. They need to read my book Roots Demystified. If they read it, they would understand that all tree roots are at least 1/2 times wider than the canopy (dripline). In a sandy soil the roots can grow three to seven times wider than the dripline.

I think the last paragraph talks about the root system and nutrients, but I can not read French. Maybe someone reading this blog could translate it for me and others. (Click on the image to get a full screen view to make it easier to read.)

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Invasion of Color

I've lived in California for 39 years. When I go back to Missouri (pronounced Mazzuhra

by the locals) in the fall I'm reminded of the amazing display of fall color in that almost

entirely deciduous forest. In California, near the coast, we have to rely on exotics from

ecosystems near and far. One of the trees now blazing away is the ornamental Chinese

Pistache (Pistacia chinensis). Here are two photos of this stunning introduction from

parts of China. Enjoy it while you can. In Texas it's considered an invasive plant.

It's showing up in Sacramento riparian habits as an escapee.

Soon to be on the hit list of the native plant enthusiasts in California.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Bean Hole Beans (?!)

It’s end of summer and the rainy season roared in with a vengeance—three to 15 inches of rain in northern CA. Great start to the rainy season. Didn’t add hardly anything to the reservoirs and thus the drought continues.

Alas, the beginning of the rainy season means the end to the “bean hole” season. I’ve been cooking beans underground in a Dutch oven buried under 12 inches of sand for 20-24 hours for over 15 years. People beg me to prepare a pot of bean-hole beans when they are invited to an evening of food and conviviality.

I started by digging hole big enough to be able to line it with bricks and still have enough space to accommodate a Dutch oven with room to spare. My hole is lined with bricks and as well as the bottom and is about 24 inches deep.

I soak the beans for at least 2 days and change the water two to four times, I cheat a bit and use a pressure cooker to soften the beans a bit, but make sure they are still firm. (These steps plus the slow cooking time seem to make for flatulence-free beans.)

The next part of the “recipe” starts with a large fire fed by scrap wood–hardwoods work the best–to develop a huge pile of hot coals and to store plenty of heat in the bricks. Takes 3-4 hours depending on the wood. (I live in dry-land forest. For protection, I make a cone of ¼ inch hardware clothe to trap the occasional drifting ember. There’s also a gravel four-foot radius circle around the bean hole for extra protection. And I hose down the nearest foliage.)

Next I take out ½ of the coals into a metal wheelbarrow. Put the Dutch oven filled with the “secret” bean mixture in with a few layers of moist newspaper to protect from getting sand in the Dutch oven. Then the rest of the coals go back on top of the Dutch oven. Sand is added to mound up to 12 inches above the top of the Dutch oven. The beans slow cook for 20-24 hours for eating the next evening.

[Footnote: I found some discarded clay features that look like a large spine. I added them next to the bean hole to prove this was an ancient BBQ place dating back generations and when lost Italians in the 1800s (many of my neighbors are Italian) stopped to feed themselves.]

Here, never revealed before is my “secret recipe” for the bean-hole beans.

Bean Hole Beans Recipe

2# beans, kidney, black, or white (slightly pre-cooked in a pressure cooker)

½# bacon (Can be deleted by vegetarians, vegans, the overweight, or potential heart attack victims.)

3 TBS Mustard

¾ TBS black pepper, freshly ground

½ cup dark molasses

2 (or more) large heads of garlic, peeled and diced into big chunks or left whole

1 cup of your favorite hot sauce

1TBS chopped rosemary leaves

1 TBS or less, fresh-ground French roast coffee grounds (The real secrete ingredient.

Combine all the ingredients and fill the Dutch oven.

My oven is big enough to feed six to eight people, depending on their waist size.

You can cook the beans for hours in a Dutch oven in an oven. But where’s the fun in that!

Enjoy!

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Oaks, Watered to Death

I rained 4+ inches yesterday. This got me thinking about water and native coastal oak trees.

I live in the arid Mediterranean zone of California where the oak trees get no rain from May through September. To native oaks, summer water is a poison which can quickly kill. These trees spent a millennium, or more, evolving to thrive without summer rain. In the process, oaks were able to tolerate a number of hitchhiking fungal hosts. These predatory mycelium—examples include crown, armillaria, and heart rots—need two things to thrive: moisture and warm soil. As evolution arranged it, the soil is plenty moist during the wet California winters—but too cold to promote fungal growth. During the dry summer, the soil is warm enough to stimulate fungal growth, but the upper layer of the soil has dried out enough to retard most fungi. These seasonal alternations insure that there's very little time when both necessary ingredients are in abundance together. Thus whatever limited amount of fungus survives is not enough to threaten the 300 year life expectancy of the oak.

Adding irrigation in the summer insures the rapid growth of the sometimes fatal fungi. There is little more unnatural than watering beneath a oak tree in the summer. Such trees can die from rot in 25 to 50 years—a rather quick demise for something that could live another 100 to 300 years. Most houses are owned by two or three families in the quarter century it takes the tree to slowly die. Thus, the actual culprit who installed the irrigation system isn't around when the tree meets its brutal end.

One of the debates about oak trees revolves around how far away summer irrigation should be kept from an oak's trunk. The conservative answer is a zone free from summer irrigation for radius of six to eight feet from the trunk. Yet the more prudent gardener would agree that an unirrigated area equal to the width of the canopy—called the dripline—is the minimum distance. As described in my book Roots Demystified, the greater portion of any tree's roots, especially the majority of the tiny absorbing root hairs, are well beyond the dripline. In a heavy clay soil; roots, as a general rule, roots growth half again as wide as the dripline. A sandy soil, because of its lower resistance to root penetration, allows tree roots to grow as much as three times wider than the canopy. If nature selected oaks for no summer water, than the natural landscaper should avoid all summer water within the entire root system—up to three times the canopy's width, or more. Alas, if there are two or more oak trees on the typical suburban yard, this means the entire yard should be irrigation free—period. This brings up the delicate art of denial. Most homeowners rationalize—if they even give it any consideration—that some lawn or a few irrigated shrubs under part of the oak's foliage is alright. But this does shorten the oak's natural life—period

Fortunately, nature has developed plenty of species of plants which thrive beneath California oaks without summer moisture. The trick is to plant these special plants in the fall, in October or early November, so the winter rains can establish a healthy root system before the parched winds of summer arrive.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Persimmons & More

I love persimmons. The first crops are coming into the specialty supermarkets. Soon, I'll be eating some from my own trees. I was fortunate enough to visit and taste some of the 81 varieties in the Wolfskill collection near Davis, CA.

The photo on the left documents that foggy, exciting day. The one on the right is just a few of the rare varieties of persimmons.

The Wolfskill collection is a fascinating occurrence between the private sector (Francis Wolfskill’s) and the public sector (the University of California at Davis.)

In 1934, when John Wolfskill’s daughter Francis died, she left approximately one hundred and seven acres of the grant to the Department of Pomology of the University of California, Davis, with the understanding that the property was to be used as an experimental horticulture station and the line of olive trees planted by Wolfskill in 1861 was to remain standing.

The collection is a virtual Noah's Ark of common and uncommon fruits and nuts such as:

As of 2009:

Actinidia (kiwi) 79

Diospyros (persimmon) 81

Eriobotrya (loquats) 36

Ficus (figs) 303

Juglans (walnuts) 552

Morus & Maclura (mulberries) 69

Olea (olives) 148

Pistacia (pistachio) 239

Prunus (all stone fruits) 1457

Wingnut (Pterocarya stenoptera, used to develop rot-resistant walnut rootstocks) 31

Punica (pomegranate) 180

Vitis (grapes) 3113

TOTAL # of varieties in the entire collection = 6309

USDA National Clonal Germplasm Repository (NCGR),
Wolfskill Ranch,
4334 Putah Creek Rd., Winters, CA

Here’s how to get some scions for your edible landscape:

Almost all plant material from the Davis gene bank is distributed as cuttings and deadlines for orders are those appropriate for such cuttings. These cuttings must be rooted or grafted/budded to produce a plant. Material of Juglans, Pistacia, and most Prunus are very difficult to root and the recipient must obtain appropriate rootstocks prior to receipt of scion cuttings.

Domestic orders are sent Priority Overnight by Federal Express. A packing list and certificate of quarantine compliance are shipped with the plant material when required. When orders are shipped within the U.S, it is necessary for the recipient to obtain and submit a Fed Ex account number. Fed Ex account numbers may be obtained by calling 1-800-GO-FEDEX.

Please indicate dormant cuttings, budwood/scionwood, or summer cuttings or budwood. Please use accession numbers when ordering material. Orders for dormant cuttings or budwood must be received by December 1^st, and are shipped in January/February. Orders for summer budwood/cuttings and open-pollinated seeds must be received by May 1^st, and are shipped in June-August. Orders for pollen must be received by January 31^st, and are shipped at appropriate times for each crop.

*Summer request for Punica and Morus germplasm should only be made if propagation will occur under mist.

*Due to great demand for dormant cuttings and their higher rooting success rate, we will no longer have routine distribution of Ficus summer cuttings.

Please be sure to include a phone number, email address, and Fed Ex/DHL account number.

Orders must be submitted via email to Bernie Prins (bernard.prins@ars.usda.gov)

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Santolina

Some sub-shrubs last–even thrive–in our deer-ridden, drought-resistant landscape. One of my favorites is Santolina. Lavender Cotton better known as just Grey Santolina (Santolina chamaecyparissus) shows up in most of my designs as it is also free of pests. Pictured on the left is a mixture of Grey and Green (Santolina virens) Santolinas in bloom. This was planted in 1983. The photo on the right is 26 years later. The foliage was still in pretty good shape. Down at the base is a trunk over four inches in diameter. Pretty good life for a wonderful plant.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Spooky

It’s getting to be Halloween time. Here’s a fun arrangement from Maxine’s eccentric garden. Always the theme of death in eccentric gardens. As mentioned in my blog of September 14^th 2009. Enjoy.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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

Shame on Bambi

Oh deer! (Old pun. Sorry) The bane of a forest gardener. As discussed in my blog of May 4^th 2009, lots of plants that were deer resistant in my garden are now readily consumed or dead. I lost all my red-hot poker plants (Kniphofia uvaria), also known as torch lily, over time. They went untouched for maybe 12 years when the deer started to nibble on the leaves. Soon all the leaves were eaten to the ground and no flowers ever formed. They were eaten so severely that the plants eventually died.

Now 10 years later it’s all starting over. The victim this time is the fortnight lily (Dietes iridioides). What’s so amazing is that one plant is untouched (on the left) while, only 40 feet away, another fortnight lily is being heavily grazed. Notice the number of severed leaves on the right. I predict that it will take only five years or less before the plant is too heavily browsed to survive. I like this perennial plant as one of the few straight, vertical lines in my garden. Drat. I’ll have to come up with another “deer-proof” vertical accent plant for these two guardians of the straight lines.

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

Visit my web site to learn about my new book on drip irrigation and other gardening books.

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