But even in severe areas, or with plants of questionable hardiness, there are some ways we can increase the odds against winter-kill. Selection of suitable varieties, careful planting in favorable locations (never in low “pockets” where frost settles, or where water collects around roots under eaves or around walls), careful fertilizing, winter protection, prevention of attacks by insects and disease—all of the cultural principles that promote healthy, thriving growth, will help to increase winter hardiness. In other words, “The combined effects of all (climatic and cultural) factors determine the true plant adaptability.”
Actually, true hardiness means more than mere winter survival. A tree or shrub is hardy when it can live through many years to maturity, and when it not only survives but develops normally and completes its annual growth cycle. For example, in some sections, very late or very early frosts will kill flower buds on some varieties. Trees and shrubs that require a period of winter dormancy are not hardy in Florida, where there is no protracted cold period. In arid areas where summers are extremely hot, dry, and windy, hardiness may depend on how much time you have to spare for special care.
If you would avoid disappointment, especially with rather expensive miniature trees and shrubs, buy the strongest, healthiest plants of the varieties most suitable to your climate, and do all you can to satisfy each individual’s cultural needs. Thus, unfavorable weather has two strikes against it from the start.
PLANTING AND CARE
No matter how careful we are, fall planting is seldom successful for us in Connecticut. But in spring planting it seems as if we can’t miss. Once we were given a dozen ornamental shrubs—named varieties of virburnum, lilac, and two of the supposedly tricky caryopteris—whose bare roots had been out of the ground for several weeks. The caryopteris and one invincible lilac even flowered that year!
In early spring, just before they awaken from dormancy (or a little later when new growth and buds are starting to show), woody plants have more vitality than at any other time of the year. Vigorous new roots grow faster. And the plants have a full growing season to get established before winter sets in. We start planting the minute the soil dries enough to be workable, sometimes as early as March. Of course, spring-flowering varieties are safest if they are container-grown or balled and burlapped.
Early fall planting is fine for milder climates—from the time the season’s growth has matured on evergreens, or when deciduous varieties begin to drop their leaves, until the ground freezes. Except for container-grown plants, winter planting is usually recommended for the South, when the plants are as nearly dormant as possible.
Bare-root plants (risky for evergreens) should be kept moist until they are put into the ground. Thoroughly soak the roots, and even the stems, in a bucket of water. The roots and soil of balled and burlapped plants should also be kept moist. Either way, protect the transplants against wind and sun until they’re set out.
Dig a planting hole wide enough for the roots to spread out in without bending or crowding, with an extra six inches of loosened soil in the bottom for them to penetrate. This is the time to check on drainage, one of the most important factors in plant survival. Run some water in the hole—enough to fill it. If the water seeps away fairly fast, the drainage is probably good. If it remains for any length of time, you’d better dig much deeper and remove the subsoil. Fill in with sharp sand or fine gravel for about six inches.
Enrich or condition the topsoil that you dug out, before you replace it around the roots. Set trees and shrubs at the same level they were growing in the nursery, never more than an inch or so deeper. The burlap around a soil ball doesn’t need to be loosened. It will rot away rather quickly. Fill in around the roots until the hole is three-fourths full; flood with water to settle soil in any air pockets; let it drain; and finish filling the hole until it is just level with the surface, but don’t mound it up. A raised ridge around the edge of the hole will form a saucer to hold water until it runs down to the roots. Water again, slowly and thoroughly, so that the soil in the hole and some of the surrounding area is thoroughly saturated.