There are too many trees in Washington gardens, probably because Americans are brainwashed in elementary school to the notion that trees are sacred. They are not.
Trees are, obviously, glorious creatures in their place, but then so are tigers, and we do not insist that every garden have six tigers in it.
In small gardens trees make it impossible to grow almost everything from roses to zinnias, and this may be the place to bash once again the absurd notion that shady gardens can be a blaze of color.
That notion is a favorite of the more simple-minded gardening articles in careless magazines. When you get to the brass tacks of the piece you find that this shady garden blazing with color is in fact not shady. Usually there is a crab apple tree to one side, or in the foreground of the picture, to suggest trees and shade; but the garden is essentially sunny, and that is why they have all those flowers there.
Sometimes through fate, quite grim fate, a garden is irremediably shady. This often happens in congested places like Georgetown, or in slums in general, and the gardener must make the best of it, giving thanks he has any outdoor space at all. Such gardens can, of course, be beautiful, just as a one-room apartment can be beautiful. But the limitations are severe.
In a 20-by-25-foot shady garden the obvious thing to do is pray to the god of architecture, and he will often save you. Cardinal attention in such a garden must go to the walls or fence, to the open space at the center, which should be paved as handsomely as means permit, and to one (not a dozen) dominating feature such as a fish pool, a wall fountain or a piece of sculpture of the highest quality (at least in the eyes of the gardener). Then, in what amounts to a shady outdoor room, there can be such architectural (but quite inexpensive) items as an arbor, a handsome bench set between pillars or posts on which shade-enduring vines grow, arches covered with vines of elegant foliage such as the akebia. Grapevines also endure surprisingly dense shade, though they do not fruit well, but usually well enough to provide excitement for the mockingbirds.
There can be tubs or urns (fiberglass specimens are lightweight, durable, relatively inexpensive and an excellent choice). Only shade-enduring plants can be grown in them, but pots of flowers can be sunk and they will provide color for some days before being replaced.
The pool, by the way, will not get enough sun in heavily shaded small gardens for waterlilies, but a clump of water hyacinths will usually do nicely. In any case, common red goldfish alone will provide endless interest. If the gardener does not find goldfish endlessly interesting, he should learn to do so.
All of which is very well, but the gardener in such a site should forget lilies, roses, irises, peonies, and plan on achieving beauty by less flamboyant means, with hellebores, hostas, ivies (sadly neglected, by the way) and even tropical foliage plants that must be brought in for the winter. Still, all the usual house plants like tropical ficus, schefflera, bananas, small feather palms and dracaenas can produce striking (sometimes too striking?) effects in the shady courtyard all summer.
Perhaps, in gardens so small as 20 by 25 feet, it could be argued that gardening is so limited in scope that it makes no difference whether it's in heavy shade. But I have mentioned some of the obvious possibilities of such a garden to keep those who have nothing better from falling into despair.
In larger gardens, maybe 50 by 100 feet, the gardener often goes mad and confuses his eighth of an acre with the great outdoors. For some reason, which may have to do with tree worship among our ancestors, he is likely to plant a few trees. He should not.
I yield to nobody in my love of oaks, beeches, sycamores, sophoras, ginkgoes and other noble trees of great size, but they are not easily managed on small lots. I grew up in a garden that boasted a pecan tree nearly 100 feet high, planted from a seed, but in the 50 feet surrounding it we finally concluded (even though the pecan does not make dense shade) the best thing was to mass drifts of daffodils for spring, a few hundred Guernsey lilies for fall, and let it go at that.
If a tree is needed, then, the two best choices are the common dogwood and the Washington thorn. Both are beautiful throughout the year. Other sensible choices are the Sargent crab, which is usually a good-sized shrub rather than a tree, witch hazels, persimmons, sourwoods, shadblows and our wild red cedar. The star magnolia, which rarely surpasses 16 feet, is another admirable ornament, and the smaller hollies are fine.
It is usually a mistake to plant a batch of fruit trees, though in size they do well when on dwarfing stocks. I find it hard to live without a peach tree (in the city squirrels and rats will get all the fruit if the gardener does not take heroic measures) and an apple of some kind. But the gardener must recognize that such trees are not particularly handsome apart from their flowers and fruit, while the dogwood and thorn are ever-handsome.
If you must have an oak or one of those wretched Norway maples at least plant it in the center of the garden and build the garden around it, thus sparing neighbors as much as possible from the effects of folly.