By Cathy Caldwell
Piedmont Master Gardener
Creating a backyard forest is a fast-growing movement, inspired in part by the desire to mitigate the effects of global warming. No doubt, another motivating factor is author Douglas Tallamy’s vision of an immense homegrown national park, consisting of interconnected backyards filled with native trees, shrubs and perennials that provide habitat for insects, birds and other wildlife. If you’re interested in joining this movement, take a look at the September issue of Piedmont Master Gardeners’ monthly newsletter, The Garden Shed, to find practical advice and links to many helpful resources. (Click on the monthly newsletter tab at piedmontmastergardeners.org.)
A long list of benefits come from the backyard forest, including: 1) removal of air pollution through particulate reduction and respiration; 2) food, protection and habitat for pollinators, birds and other wildlife; 3) increased oxygen production; 4) reduction of stormwater runoff and filtration of the excess nitrogen and phosphorus it carries into streams and rivers; and 5) soil erosion prevention.
Trees also absorb and store heat-trapping carbon dioxide. Although backyard forests may not make a huge dent in our greenhouse gas emissions, they nevertheless will help. Moreover, they provide energy-saving benefits that curb fossil-fuel consumption. For example, three or more large deciduous trees on the sunny sides of a house can reduce air-conditioning usage and costs by as much as 30 percent during the summer. Conifers planted on the north side of a house will reduce heating costs by blocking winter winds.
Replace Your Lawn with Forest
If you’re eager to replace some turfgrass lawn with a forest, start with a bit of planning. First, lay out your site, making sure it won’t interfere with other uses in your yard, such as a septic field (definitely no place for a mini-forest) or a play area. Consider these questions: How will your new forest relate aesthetically to other nearby land, wooded or not? What’s the sun exposure of the site? Is your soil loamy or heavy clay? Have you tested your soil? Do you have areas that tend to be wet? Once you have answered these questions, there are several ways to proceed.
Plant a Few Trees and Add a Few More Every Year
This is not the quickest way to develop a forest, but it will work just fine. Be sure to remove enough turfgrass and weeds around each new tree so that its roots have ample room to grow. Two to three feet is best; you don’t want your tree to have to compete with grass roots for water and nutrients. Mulching all around the tree (except right next to the trunk) will be even more important in the hot, dry times.
Create planting beds for new trees by using a grass-smothering technique such as sheet mulching or solarizing, and then plant new trees into the mulch. Sheet mulching (a.k.a. lasagna gardening) slowly converts green and brown organic material into a planting bed for your trees. Solarizing involves covering the grass with plastic, which basically “cooks” the grass and some weed seeds. For gardeners concerned about the amount of plastic involved, the alternative is to smother turfgrass with a variation on sheet mulching, such as a six-inch layer of wood chips, 4-by-8 pieces of plywood, or a layer of newspapers 20 sheets thick with wood chips on top.
If native trees grow nearby, and if tree seedlings pop up here and there in the yard, it’s probably a good candidate for this method, if the soil is not too compacted. Basically, you sit back and let natural succession create a forest.
No matter what method used, watering, weeding and removing invasives will be essential. After your forest has a canopy, it will shade out most weeds, and the forest floor will be covered with leaves, which will discourage most invaders.
Choose Native Trees for Your Backyard Forest
You’ll need to do some homework to identify the best trees for the soil and sun exposure in your yard. Select several kinds of native trees and native shrubs, and consider adding native ground covers, such as ferns.
To be part of Doug Tallamy’s homegrown national park, at least one kind of oak is a must. As you consider which type of oak will suit your site, keep in mind that all oaks will do well in rich, well-drained soil. If you have thin or dry soils, scarlet oaks and white oaks are usually the best choice.
Start with Seedlings
If you have a large yard that will require more than a few trees, you can purchase inexpensive bare-root seedlings from the Virginia State Forestry Nurseries (www.buyvatrees.com). Admittedly, they will be tiny, but within just a few years they will catch up with larger trees planted at the same time.
The Virginia State Forestry nursery across the Blue Ridge in Crimora opened for business in October, and you can order now for shipping or pickup beginning in February. Early spring is the recommended time for planting these little seedlings, while they are still dormant. Be prepared to plant them immediately, and have ready tree tubes or wire mesh shelters to protect them from deer.
Create a Food Forest
In our region, a food forest combines such trees and shrubs as sassafras, pawpaw, redbud, American hazelnut, persimmon, fig, highbush blueberry, elderberry and raspberry, among many others. In 2012, George Mason University embarked on a project to turn a grass lawn on the campus into a food forest employing principles of permaculture. By 2017, the project—called The Innovation Food Forest—was flourishing. For photos and a plant list, visit green.gmu.edu/campus-sustainability/campus-gardens/ff-home/.