Three forests

Northeastern North America wants to be forest: we’ve got a temperate climate and moderate rainfall, and before people settled the area in large numbers, there was pretty much unbroken forest. Areas that burned or blew down would revert to forest as soon as the trees had time to grow again. If you leave a strip of land alone today, you’ll get forest. Forest is a given.

So forests are the basis of our ecosystem. And they provide invaluable services: they clean the air, moderate the temperature, and slow the flow of groundwater, which reduces flooding. If you’re trying to create a more sustainable and natural environment than the typical suburban backyard, you’re probably going to replace some lawn with trees and shrubs: you’re going to plant a forest. So let’s talk about forests.

Forests are ecosystems, so they contain plants, animals, fungi, soil, rock, and water. They have a three-tiered structure: a canopy layer made up of tall trees; an understory layer made of immature trees, low-growing trees, and shrubs; and a floor made up of ferns, grasses, and flowering plants. Vines tie the layers together. There are all different types of forests: wetland forests, upland forests, northern and southern swamp forests, each with distinctive suites of plants and animals. If you see oaks and hickories in the canopy, look for flowering dogwood, blueberries, and mapleleaf viburnum in the mid-height layer; wild turkeys and blue jays eating the nuts; and, in spring, lots of native wildflowers.

Here’s a picture of a nearby upland forest at Campgaw Mountain Reservation in Mahwah:

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This is a lovely mixed upland forest made up primarily of oaks and sugar maples. But note how open it is. The shrub layer and understory are mostly missing, because there are too many deer and not enough predators. and because the native shrubs and wildflowers are missing, many parts of this forest are overrun with invasives. The slight tinge of green you see on the forest floor in this picture is stiltgrass, a highly invasive Asian grass that’s taken over in many local forests.

As a comparison, here’s a nearby forest with much of its structure left intact:

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This is the Thielke Arboretum in Glen Rock, which contains a beautiful wetland forest. The canopy is quite mixed, but the dominant tree is red maple. The understory includes spicebush and clethra, and the forest floor is very diverse, with several species of ferns and many different wildflowers that bloom from early spring through fall. Invasives are continually coming in from all sides (and from the sky, as birds drop their seeds), but volunteers keep at least a small area clear, and new natives continue to pop up. This forest is a treasure; I encourage you to visit it in all seasons.

Here’s the third forest I want to show you. You’ve seen this picture before:

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This is my backyard miniforest, which replaced a hot, sunny lawn. We planted the trees and shrubs, a mixed bag of canopy and understory trees chosen for maximum diversity in a very small space; the understory came up on its own once the grass died. Violets, ferns, native grasses, common lobelia, and Virginia creeper all popped up once we stopped mowing. English ivy, Norway maples, and lots of lawn weeds continue to pop up as well and must be weeded out each spring, but that’s the only maintenance the forest requires (except for winter pruning every two or three years). Most suburban homeowners could create something like this and let their land become what it wants to be: forest.

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