So now our project was a blank slate, down to the soil, mostly, and it was time to plan what would be in the new Park. Those who strive to duplicate the natural environment learn that a woodland (or a rain forest) has multiple layers of plants from the tallest trees up to a hundred feet or more, down to mycorrhizal symbiosis between fungi and roots of all the plants, which microscopically extend under healthy soil.
Your Park (or garden, or yard), if it aspires to being a woodland, should have layers from high to low. Tall trees, understory trees and shrubs, perennials and ephemerals, ground covers, and both evergreen and deciduous plants. No, it isn’t overwhelming, though your choices are many. First, is to decide what is your plant hardiness zone. They are numbered—in Baltimore, we’re on the cusp between zone 6 and 7 (lower number is colder zone). When you choose to plant something, this listing will tell whether it’s likely that the plant of interest will thrive in your zone. But, even within a very local area, the zones can differ. From downtown Baltimore to its suburbs plant survival differs dramatically.
With the warming of the planet, we must now take into account that during the life of a tree planted this year, its climate will be substantially warmer later. To have that tree survive 50 to 100 years from now, it should be one natural to an area considerably south of its location now. In Baltimore, the TreeBaltimore group , for which we do volunteer work, is today planting trees native to North and South Carolina. http://treebaltimore.org/resources/ (Look for the Baltimore City Tree Species List, as one example of how to select trees that will survive and contribute to your yard and environment). The Maryland Department of Natural Resources has a web site describing the types of trees that are desirable, and will now plant some in your yard, free!
There are very active diseases and invasive pest infestations of some trees that make them a high risk choice. The ash borer will probably decimate the white ash trees of the Northeast. The wooly adelgid is finishing off the hemlocks. And, while there are some Dutch elm disease resistant varieties (“Princeton”) now available, their true longevity is an issue.
Trees are slower or faster growing, some do best as “top dogs” growing tall, while others are shorter and live well under the wing of big guys (understory). Maples give deep shade and are so densely rooted that few plants do well growing within the “drip line” (the area under the outermost leaves). Trees can have nice fall color, or even better, they can produce food for bees, birds, and mammals. Prize trees in an ecological sense do all of these good things. One of the 4 star trees in this regard is the black cherry (Prunus serotina), which has nice flowers (for pollinators and visually) and develops berries loved by many urban bird species, as well as chipmunks and squirrels.
Some of the finest trees to enjoy are not typically in the front row of the big box garden center. There, you’ll find Japanese maples, non-native maples (all variants of the invasive Norway maple), and dogwoods (more often the Korean varieties). For our garden and park, we picked instead yellowwood (Cladrastris kentuckea), ironwood (Carpinus caroliniana), black cherry, hophornbeam (Ostrya virginiana), fringe tree (Chionanthus virginicus, in picture below, showy flowers and fragrant from 50 feet away), white oak (Quercus alba, the Maryland state tree), native dogwoods (Cornus florida), and redbud (Cercis Canadensis). Since our neighborhood is named Poplar Hill, we also planted a so-called tulip poplar (Liriodendron tulipifera).
The Maryland Department of Natural Resources has a web site describing the types of trees that are desirable, and will now plant some in your yard, free! Some trees are high maintenance, some are not. For example, the disease resistant Princeton Elm sprouts about 10 times more limbs than it needs and must be pruned into the shape we remember as an elm tree. Black locust, while a native tree, throws junk from itself, including leaves, nearly all year (and has thorns). God forbid you have tree of heaven (Ailanthus altissima), a superbad actor that sprouts babies massively (and they stink).
If you have a dead tree, please leave it there. Snags, so-called, are condos for birds that cavity dwell (woodpeckers, chickadees, wrens). Dead trees are part of the natural environment and when and if they fall, logs on the ground are further fodder for all sorts of beasts with and without legs, all of whom restore the soil and are themselves food for someone else.