Late summer is a good time to consider the advantages of fall planting and the ways to ensure the best results with fall-planted material.
In the fall, the soil is warm and flaky—a condition ideal for planting and rapid root growth.
Favorable soil temperatures influence to a great extent, the behavior of soil microbes and the absorption of water and nutrients—all of which promote root development.
Root Growths in Low Temperatures
The fact that the roots of most plants continue to grow at relatively low temperatures is not generally appreciated by many gardeners.
Then, too, the rest period for roots and branches does not always occur at the same time, nor does the rest period of conifers and other evergreens coincide with that of deciduous trees.
Root growth of conifers, for example, may cease completely during very cold weather and slow down considerably during midsummer, whereas root growth in sonic deciduous trees continues at temperatures as low as 45° degrees Fahrenheit and does not appear to stop even in midwinter.
Root growth begins its seasonal rapid development a few days to several weeks before bud growth.
Because their roots are more sensitive to low temperatures, evergreens should be planted in the early fall; precautions should be taken to keep the soil warm if planted in late fall.
The soil must remain warm for a sufficient period to permit the development of additional roots after transplanting.
Many fall-planted evergreens fail to survive the first winter because their roots are not thoroughly established in their new location before very cold weather arrives.
Spring-flowering plants, particularly rock-garden plants, are also best planted in the fall. These will then have ample time to develop new roots, thus permitting the plants to throw their full strength into spring blooms.
Fall Planting
Anyone who has planted roses in the northern part of our country in spring and fall knows that a whole season in flower production can be gained by fall planting.
In the spring, the roots of plants set out the previous fall become active days or even weeks before top growth begins.
More vigorous plants develop where the roots begin to work well before the tops. Just the reverse frequently occurs with spring-planted material; the top growth is well advanced before roots become active, and the plants are, therefore, not as vigorous.
Transpiration Process
Some vital processes in trees and shrubs never cease. The process is known as transpiration or loss of water. For example, it goes on continuously. Even in midwinter, moisture is constantly being lost by plants.
Deciduous plants lose relatively small amounts during the winter, but evergreens lose considerably more; those growing in exposed locations lose far more than those in protected areas.
Broad-leaved evergreens such as Andromeda, mountain laurel, large-leaved American and Chinese hollies, and rhododendrons suffer the most.
Late winter and early spring are the times when most of the damage due to excessive water loss occurs.
Air Temperature
A slight rise in air temperature will cause leaves to lose excessive amounts of water at a time when, because of low temperatures and other factors in the soil, the roots cannot absorb enough to make up for the loss by the leaves.
As a result, the leaves wilt, and if they remain wilted for too long, they turn brown.
Under similar circumstances, a rise in air temperature will break the dormancy of buds and start them growing. With a sudden drop in temperature at night during late winter or early spring, the newly emerging growth freezes.
Bloom failure in azaleas, peonies, and many other early-flowering plants often occurs under such conditions.
Soil Moisture
Another factor in successful transplanting is an abundance but not excessive soil moisture. Perhaps the most common mistake over-zealous gardeners make is overwatering the soil around newly transplanted trees and shrubs.
Excessive soaking of the soil around newly transplanted material may retard the development of new roots and, in many cases, may even contribute to root decay and the eventual death of the entire plant.
Mulches Are Helpful
A mulch is highly desirable around fall-planted material. However, one that tends to keep wet and become matted should be avoided, especially over the crowns of perennials.
Authorities seem to disagree about the proper time to apply the mulch in the fall. One of our best-known horticulturists says that mulch should be applied immediately after transplanting in the fall because it will help keep the soil warm and prevent any rapid temperature change conditions most favorable for root growth.
Another argues that if the mulch is applied too early, it will become a nesting place for mice and other rodents.
He says that if the mulch is applied after the ground freezes hard, the mice will have found other homes for the winter.
Moreover, he claims that mulches that are applied early constitute a fire hazard when they become dry. Both of these possibilities can be minimized by keeping the mulch well away from the tree trunk.
Another group of horticulturists maintains that fall mulches should be applied after the soil is frozen hard.
They say that mulch is not so much a protection against cold as it is against the alternate freezing and thawing of late winter and early spring, which causes plants to heave out of the ground.
I believe a good case can be made for either school and that each gardener’s particular situation will determine the advisability of early or late mulching.
Water Loss from Leaves
Loss of water from newly transplanted material, especially evergreens, can be partially overcome by spraying with Wilt-Pruf either before or immediately after transplanting. Wilt-Prof contains plastic particles suspended in a water solution.
When sprayed on the foliage, it dries in twenty minutes to a glossy, firmly adhering film, which is effective for a month and partially effective for three months except where the leaves expand after it is applied.
Although Wilt-Pruf facilitates transplanting, reduces transplanting shock, and reduces the chances of winter drying, it should not be considered a substitute for good gardening practices.
Carelessly handled plants and those with poor root systems will not survive transplanting shock nearly as well as those that are properly handled and have an adequate root system.
Lastly, and above all, the major key to successful transplanting is good soil drainage. Poor soil drainage is the most common cause of the premature death of perennials and other plants.
Although a few plants will thrive in wet soil, the great majority die rapidly when their roots are kept wet for more than a brief period or if they are frozen into a solid block of ice.
44659 by P. P. Pirone