Ah, gardens - myriad shades of green leaves, endless varieties of flowers, fruits, vegetables, tall majestic trees . This is what most people think of when they think of gardens. But none of these elements are as important, or as misunderstood, as the parts of plants hidden from our view - the roots.
While the leaves convert sunlight to sugars and carbohydrates and send them down into the roots, the roots in turn absorb water, minerals, nutrients and other compounds from the soil and send them up to the plant. In a healthy plant, the system is balanced.
Most people select plants at a nursery by how healthy the leaves and flowers look. Big mistake, according to Dr. Mike Amaranthus, president of Mycorrhizal Applications, Inc. of Grants Pass. With a doctorate in soil microbiology, and a 31-year history of working in the field, few people understand roots and their needs as well as Amaranthus.
Plants need several types of roots. Some have long thick taproots. Then they have smaller, structural roots, which serve to anchor the plant in the soil. Smaller, yet, are the hairlike feeder roots.
"A lot of plants from nurseries have structural roots but not feeders," Amaranthus says. "They baby them, bathe them constantly with water and fertilizer. This makes the plants produce a lot of above-ground biomass, but they don't have the balance of roots and shoots they need to survive in the real world. They are like little junkies - you have to keep feeding them chemicals or they won't make it. Ultimately you want to achieve a balance between what is above and below ground. Until you achieve that, the plant is always under stress."
Amaranthus believes the secret to healthy plants and roots is good soil. Increased urbanization destroys soil by stripping it off when building, compaction through use and overuse of fertilizers and pesticides. "We treat soil like dirt," Amaranthus only half jests.
While many perennials have roots that can take a lot of manipulation - cutting and dividing to produce new plants - most trees and many bushes need to have their roots treated gently.
"The rule of thumb," says Charles Brooks, owner of Brooks Farms and Gardens in Grants Pass "is anything bigger than 1 inch in diameter constitutes a major root and should be treated as such. Try to excavate around it without hurting it. If you absolutely have to cut a root then cut it cleanly, don't leave it torn up. A clean cut allows a clean scar. Torn roots tend to kill a plant. Of course some plants, like birch trees - any cutting into the roots will damage the tree severely."
Brooks recommends cutting back both the roots and plants when transplanting to keep the system in balance. He also bemoans people who suffocate trees by piling extra dirt on top of established root systems to create beds under trees. (Mulching is helpful, though.)
Amaranthus, when discussing transplanting, adds advice on hole size, saying a hole substantially bigger than the root system is best, as it gives room for more feeder roots to develop. Adding compost and organic material in the hole is also helpful, but he recommends against putting fertilizer in a transplant hole unless it is organic or slow-acting, time-release type.
"Give a tree three to six months after transplanting before fertilizing, and never fertilize heavily," Amaranthus says. "(Fertilizers) are salts and they build up in the soil. That's a sure way to kill your soil."
Pay attention to above and below ground parts of your landscape plants. The reward is healthy lush vegetation that can take all the surprises and stresses the Rogue Valley climate can give it.