While you’re conditioning soil, make sure there is good drainage. Only bog plants will grow with their roots in muck or standing water. You may need an initial layer of fine gravel or course sand. Raising the surface of the garden will also help.
If you think that the importance of suitable humus-rich soil is either exaggerated or overrated, think also of this: With the type of light and humus (usually acid) in which they grow naturally, woodland plants will settle down contentedly in your garden and establish families and colonies that increase every year. If you don’t provide it, they’ll get homesick and pine away. Not only that, but once they’ve made themselves at home, they’ll require practically no care. They don’t want to be cultivated, fertilized, weeded, watered, mulched, or given special protection in winter, as long as there are trees that drop leaves. The most you might have to do will be making sure the leaves aren’t blown away, or, if there are no trees, lugging in leaves from somewhere else.
PLANTING
Although plants are chosen for any garden according to light, soil, moisture, and other cultural requirements, woodland plants permit less leeway than most others. This is a matter of ecology, defined as “the total impact of the environment and the plant’s accommodation to it.” Some delicate plants are, of course, less adaptable than other more rugged species. Check catalogues, reference books, and other sources to learn all you can about each plant before you plant it.
A quick word about shade. There is full shade, or deep shade, created all year by evergreens, walls, or buildings. And there is woodland shade created only in summer by deciduous trees. The hill near our house where rattlesnake plantain, pipsissewa, and pink lady-slippers grow is dark and cool in summer, but bright in spring, fall, and winter when the trees are bare of leaves. This is an important distinction.
In the interest of conservation—American wild flowers are threatened not only by bulldozers but also by thoughtless, criminally careless humans—private woodland gardens often become the home for plants dug from the wild. Last fall, one of my dearest friends methodically moved dozens of maidenhair ferns into a tiny bit of woods on her property to save them from extinction when their fronds were being picked in bunches to fill out bouquets. But this is conservation only when the plants are transplantable (a number of the most precious species are not) and are moved to quarters with growing conditions to their liking. Otherwise, they might as well die where they are.
In digging woodland plants, always dig deep and take as much of the surrounding soil as possible, and disturb the roots as little as you can. Protect the transplants against drying sun and wind until they are set in their new homes. If you can dig them with the roots intact, you can take most plants at any time during the growing season. The safest times are immediately after flowering or during fall dormancy.
Unless it is a matter of conservation, I never dig woodland plants. I buy them (they’re surprisingly inexpensive) from a local nursery or from several mail-order specialists. The nursery plants are pot-grown, and even fussy types transplant without loss. By mail they arrive bare-rooted—in early fall for all but the summer and fall varieties—but crisp and lively in their packing of moist sphagnum moss. Sometimes they even start to send out new roots and sprouts en route. If I can, I get mail-order plants into the ground before dusk on the day they arrive. Soil around transplants is kept moist and mulched with leaves until they take hold.
Years ago some suppliers collected the plants they sold, and some sources of slow-spreading types were completely devastated. Today, I believe, specialists grow their stocks of woodland plants, either under glass or in woodsy nurseries. They’re doing more to preserve these native treasures than to annihilate them.
The best of all sources is by propagation—seeds, cuttings, division of wild plants—because you’re not only increasing the population, but you’re also starting with plants that from babyhood are accustomed to your growing conditions and don’t have to make difficult adjustments. Even though it may be slow, this is the only method for a number of nontransplantable species.