Plants Really Drink and Eat Near Our Toes.

I consider those ever-popular metal tree root deep-feeders as virtually useless and mostly harmful.

Spring has been warmer than past years up here “on the mountain”. Friends are thinking about watering. I hope they think carefully. (My plants and trees receive no summer irrigation. But that’s another blog altogether.)

The roots of many plants, it turns out, don't really get most of their water and nutrients from the deep regions of the soil. Rather, most plants, tree and shrubs gather all the moisture and nutrients they require from the top 12- to 36-inches, depending on the plant. The first foot is the most critical. Here is where the soils are most aerobic and this facilitates the exchange of nutrients from the minerals into soluble form that plants can absorb. Feeding root hairs actually grow up toward those first moisture-laden nutrients. (The lettuces pictured here can send roots as deep as four feet--if you don't have gophers! This is why boxes with wire bottoms should be 24-inches high instead of 12 inches. To give the roots "room to move". Yet the lettuces still get much of their "food" from the top 12 inches. So careful irrigation is a must.)

The roots of many plants, it turns out, don't really get most of their water and nutrients from the deep regions of the soil. Rather, most tree and shrubs gather all the moisture and nutrients they require from the top 12- to 36-inches, depending on the plant. The first foot is the most critical. Here is where the soils are most aerobic and this facilitates the exchange of nutrients from the minerals into soluble form that plants can absorb. Feeding root hairs actually grow up toward those first moisture-laden nutrients. (I describe this in more detail in my newest book - Roots Demystified, Change Your Gardening Habits to Help  Roots Thrive.)

An old adage advises gardeners to water trees deeply; this often means infrequent, but lengthy irrigation. Increasingly, drip irrigation has been used as a tool for deep, occasional irrigation. Infrequent, deep irrigation tend to produce two points in the total irrigation cycle where the soil life and root hairs are damaged enough to reduce plant growth—during both the drying stage and when the soil is too wet. Dry soil kills off the tender root hairs as they can’t survive too much air. When the ground is flooded, root hairs die and noxious gases can’t escape nor pure air enter—or as pure as it may or may not be.

The metal probe of a typical deep root feeder is 18- to 24-inches long. This means that the application of the water begins below almost the entire zone of maximum water and nutrient uptake.

Good pore space makes for healthier plants. An ideal mineral/humus/pore structure balance results in a crumbly soil that allows water to percolate down, harmful gases to vent out, and refreshing air to permeate the soil. Soil breathes 24/7 at a lumbering, beneficial rate we cannot see. A soil with a healthy structure allows for easy and deep root growth and will produce the best-looking lawn, garden and tree growth.

Root feeders flood the pore space of the deeper soils, which quickly becomes flooded and anaerobic. Sometimes the deep soil saturates and the irrigation water backs up toward the surface so that more shallow soils actually get waterlogged. It's a bit backwards to send the water through a 24-inch deep probe just to apply the water 6- to 12-inches deep!

I recommend you just toss your root feeder—actually, recycle the scrap metal parts. (China could use them.) A good sprinkler can do a better job. And a drip irrigation system will promote the best growth possible—better than any other method of watering.

One garden’s “deep” soil is another garden’s “shallow” soil. Another hidden assumption about tree roots concerns the depth of your garden's soil. There are places where glacially-deposited topsoil extends for dozens of feet, but these are more the exception than the rule. If you have such a deep, loamy soil, then rejoice, but remember that the majority of moisture and nutrient absorption by trees still happens in the top two feet of the soil. Typically, most suburban yards have a very shallow layer of topsoil, if there's any left at all after construction. If, for example, there is a continuous layer of rich-orange clay some 12 inches under the ground, then the 12-inch layer of topsoil is, for all practical purposes, the only place your plant’s roots will be feeding.


Most heavy clays, whatever the color—and dark blue or pale white-gray are the worst—are relatively worthless to feeding tree roots. While clayey soil has plenty of nutrients, their availability is locked up in its tight, anaerobic structure and strong chemical bonds. Tree roots can, over many years and decades, grow somewhat into clay soils, but the number and extent of roots in the looser topsoil in far greater and more important to tree nutrition.

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


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Anti Deadhead

Martha Stewart would never like my garden.

Any act of gardening which is different than what nature would do has a negative impact, however slight. Most gardening acts are de-evolutionary—they set things back. As an example, destructive cultivation using the wrong technique can set soil back considerably. This doesn't mean we can't compensate, such as using more compost to compensate for compacted clay.

I grow a non-native lavender cultivar called 'Provence' (my garden must have deer-resistant plants) which has tall-stemmed blossoms. After their fragrant bloom is spent, the flower parts fairly quickly fall from the stalks. Most gardeners would cut back the blossom stems, called dead-heading, as soon as the color begins to wither.

As an example of trying to be more “natural”, I thought it would be interesting to see what would happen if the plants weren't pruned. So, years ago I left the slender woody stems through the winter as an experiment in low-maintenance gardening via avoidance. To my pleasant surprise, one of the first places to be garlanded with spider webs on a dewy spring morning were on the remaining naked, dead 'Provence' stalks.

Now, I leave a few of the spent 'Provence' blooms so as to insure plenty of spider web roosts. Sure, the spiders have mostly found other places from which to sling their orbs. But the more opportunities there are for these hungry predators, the better. Amigo Bob, a locally-famous organic farming consultant, calls spiders the “wolves of the landscape”.

I'm still waiting for the spiders to return in all their glory like that one special day.

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


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Visit my web site to learn about my 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

Mounded Plantings, Irrigation-Free

I’ve started the annual ritual of mulching the perimeter of my irrigation-free planted mound. I lay down 5 or so sheets of newspaper and then several inches of compost made of rice hulls and manure.


I've always wondered why the former Xeriscape Council only advocated a savings of up to 75% on the water used for outdoor irrigation. Why only 75%? Why not shoot for 100%? After seven years of trial and error, I came up with a mound-and-plant system some eight years ago which has required no additional irrigation beyond the day of planting, even during the most protracted California drought in over 100 years.

To begin such a planting scheme, I stockpiled chunky wood chips (not sawdust, which settles down too much and doesn't drain well) from local tree-trimming services. This is critical that the wood chips are mixed with the fresh green, fresh leaves, and small branches. The leafy green parts are critical to compensate for the carbon in the woodier chips.

Next, I used a spading to just crack open the soil beneath the planned area of the mound, not heaving it. Then, I built an active compost pile and plant directly on top of trimmings. Because tree chips are so high in carbon, I layered or mixed them with some manure if required—if there were not enough leaves. I'd guesstimate that a good starting ratio for your own experiments would be one part manure to three or four parts chips. I would use other types of high-nitrogen materials if needed—wet kitchen scraps, fresh grass clippings, green-manure crops like buckwheat, vetch, bell beans, and clover—to help decompose the woody chips. The more nitrogen added, the faster the mound will decompose and the greater the nitrogen supply for the growing plants. I piled this mixture of high-carbon and high-nitrogen materials at least 50% higher than I wanted the final mound to be, and sometimes up to double the height. I watered each layer as I went and made sure all material was moist.

Next, I covered the mound with a soil cap at least eight inches thick—the thicker, the better. I used a mixture of 50% rotted turkey bedding and 50% native soil for the top layer. The soil cap insures good drainage, a neutral soil temperature, balanced nutrition, and good initial growth for the transplants. The plants are placed into the soil cap and watered in thoroughly. I used five sheets of overlapping newspapers covered by turkey-bedding mulch cover the soil cap and, like a "biodegradable herbicide," suppress all weed seedlings. It’s best for me to plant in the fall so the winter rains continue to keep the composting heap moist and to allow the roots to grow. Drought-resistant plants are essential. I used white, pink, and blue rosemary, grey and green santolinas, rhue, many types of lavender, native sages, euphorbia, daffodils, and society garlic (which the deer started eating a few years later).

Once the mound started rotting, the root-hairs of the plants followed the decomposition to take advantage of the newly available nutrients. Plants are "smarter" than we often acknowledge; their roots won't grow into areas that are too warm due to thermophilic (hot) decomposition over 110 F.

Eventually, my "research" mounds settled down, the shrubs rooted fully into the native soil—the new mound is a wonderful, curvilinear feature in my landscape. Mounded plantings, which seemed to me to be a heap of contradiction at first, have become one of my preferred techniques for quick no-till soil drainage, and they don't require any drip-irrigation hardware or precious water. In hotter climates a bit of drip irrigation will probably be needed. If you experiment with this, please let me know.

There's more about planting on mounds in my book Roots Demystified.

NOTE: I live in a moderate-summer climate with a moderating marine influence. If you attempt this mound-and-plant strategy in your own area, I suspect you'll have to make some changes in plant selection and the time of year you’ll be planting. For example, I once installed a test plot at Kit Anderson’s house near Burlington, VT, when she was editor of National Gardening Association magazine. I spent hours in the muggy August heat, along with members of the NGA staff, hauling in manure-rich straw, distributing Kit's garden clippings and leaves and planting a range of perennials which normally thrive in this northern latitude (within one-half mile of Lake Champlain). Many of the crew were skeptical that such a bizarre method would work, and it didn’t—growth in the late summer was not sufficient to allow many of the perennials to weather the winter in good form. I suspect that timing was the main problem, and that mounds in hot-summer areas need to be planted in early spring so the roots can be deep enough by fall to tolerate the frozen months. You'll have to experiment in your soil and climate. I suspect the mound should be started in the Spring were there is summer rain.

Please post a comment - I want to know how the mound system worked for you.

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

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Visit my web site to learn about my 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

Cultivating an Eccentric Garden

I collect more than just plants. I gather lots of discards, a.ka. junk for my garden. I assemble various art pieces from the found objects. I especially like broken pottery.

I’m fascinated with tornados even though we don’t get them here. I’ve use cylinders of wire to both keep deer away from the newly-planted tree and as an armature for my own little eccentricities. (See the photo to the left of a cylinder around a newly-planted Strawberry Tree (Arbutus unedo).

Everyone has the seed of an eccentric garden deep inside waiting to bloom. Here are ten ways to cultivate your own:

10. Think differently. Disregard all gardening magazines, books, catalogs, and newspaper columns, and create a unique, personal style. Think about what moves you.

9. Get to know your yard. Take time to sit and walk in the space where the garden will grow; even wait through a year to gather seasonal inspiration.

8. Embellish personal eccentricities. Take pride in what makes you a bit odd. So-called peculiar traits or thoughts can be the springboard for creative thinking. If you hate pruning, for example, consider growing a “wilderness,” with hidden pathways and artistically tangled mixtures of foliage and blossom.

7. Go all out. If you enjoy a certain kind of plant or object, then go whole hog. Plant every possible variety of rose or grow hundreds of varieties of flowering plants with just shades of yellow. Collect not dozens of colorful bottles, but thousands. Display your entire collection of lobster traps among the perennials.

6. Combine unrelated thoughts to form a new idea. One eclectic gardener mixed an old toilet, potting soil, and sweet peas to create his own private horticultural joke.

5. Get inspired by “unrelated” things to synthesize new garden ideas. A childhood love of glassy-black Indian bird points (tiny arrowheads) led me to incorporate visible and hidden chunks of raw obsidian (each waiting to reveal the arrowhead inside) into my own garden.

4. Put aside normal social guidelines. Vegetables and perennials planted in the soil between a curb and a sidewalk violates the norm in many neighborhoods, but makes for a festive, unique patch you—and the neighbors—will enjoy.

3. Follow your passion. Inspired by Axel Erlandson, Richard Reames, of Aborsmith Studios in Williams, Oregon, has begun to grow a living house. About two years old, the walls are being formed by 77 Red Alder trees planted 11 inches apart in a 22 foot diameter circle—the trunks are expected to fuse together into one tree. Reames is planning to install windows and a door. Such commitment over time is best driven by resolute devotion.

2. Collect what you love, the garden will follow. Sculptor Marcia Donahue of Berkeley, California loves to collect old bowling balls. She’s massed dozens of them in her garden, tucking curious plants in and around them for a unique and striking effect.

1. Ignore all rules (even the previous nine).

Eccentric gardens open the eyes to unique vistas, free the spirit to soar to new places, and “grow” original thoughts. Nurture the soul as well as the soil with your own eccentric garden.

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

All Rights Reserved. Copyright 2008

Visit my web site to learn about more 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