Magazine article American Forests

Building Backyard Green

Magazine article American Forests

Building Backyard Green

Article excerpt

How to position, thin, and prune trees and other plants to create working layers of life from the ground up into the blue.

In my three-quarter-acre backyard in spring and summer, sunlight feeds green leaves in layer upon layer from ground level to 70 feet in the air. The leaves in turn fuel 60 different species of trees and other plants and a variety of animals.

I'm one of the animals benefitting from these working layers of green. My body runs on oxygen--the exhaust gas of living leaves. My spirit, too, benefits--from seeing the beauty and elegance of natural systems at work.

I like how my backyard looks, how it works, and how it requires so little maintenance now that everything is in place. But some maintenance and a lot of original work--plus an understanding of the "rules" of green plants--are required to establish and maintain working layers of green like this. Fortunately, many of the rules have been written down, and a careful observer can see them operate around or near his or her own home.

This I knew 11 years ago: If the Virginia pines in my backyard had their druthers, they would hog the sunlight by forming a green "tent" of leaves above everything else. By catching most of the sunlight, the pines could monopolize the area's water and nutrients because not much could grow in their dense shade. Old age, insects fires, ice, and wind would eventually tear holes in the "pine tent" and other plants would invade. but when and how?

This I also knew: I could create a more diverse and interesting plant community if I mediated between the plants struggling for space in my backyard. This meant cutting out some of the pines and pruning some branches of the remaining trees to give space and light to other plants trying to survive in the shade. And it meant moving some plants from bad to good locations and introducing others that would flourish in the new conditions.

My basic tools were a shovel, a felling saw, an ax, a pruning saw, and some clippers. My work was guided by three simple rules:

RULE No. 1: There can be only one thing in one space at one time. RULE No. 2: Living plants expand to fill the space available.

When two or more plants have applied Rule No. 2 for awhile, they inevitably start to compete for the same space. Rule No. 1 then kicks in with its absolute dictum. You will notice that there are no lawyers in the plant world. That's because plant rules have no varying interpretations and no appeal process. The plant that wins the space isn't the one with the best lawyer; it's the one that uses the best strategy to occupy a particular space for a particular time.

In this column last issue, I wrote about various plant strategies and the approach to life that trees use--they tend to compete vertically with a keep-your-leaves-above-the-competition approach. As the more aggressive trees move their leafy struggles higher and higher, shaded space becomes available below for plants that can grow on the sun, water, and nutrients left over.

Plants that can grow in the shady, reduced circumstances beneath taller plants are called tolerant. Plants that must have full sunlight are called intolerant. From years of observation, foresters have ranked trees by their tolerance of competition for sunlight, water, and nutrients. The scale goes from very intolerant to intolerant, intermediate, tolerant, and very tolerant.

Tolerance is not constant. Plants are more tolerant of competition when they're young and when there's ample water and nutrients. Near the northern edge of its range, a normally tolerant species will require more light. North of its normal range, it may do well only on warmer, sun-exposed, south-facing slopes. At the southern edge of its normal range, a species may grow only on north-facing slopes or in deep, shady valleys where it's cooler and there is less shady valleys where it's cooler and there is less exposure to sunlight. …

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