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Know Your Plants Before You Buy

Otherwise, you’re planting trouble

Every year, readers complain to me that some of their plants are flowering either poorly or not at all. That junipers, Japanese hollies and other shrubs have dead branches or worse. That their plants are so leggy. That tree roots have cracked their sidewalks. Last year, a reader asked what would cause the cement block in his basement to crack and bulge.
    As plants grow, they require more room. Some plants grow more vigorously than others. Many people plant without planning or knowing anything about the plants they have purchased. All kinds of trouble results.
    Crowding is one the consequences. Few gardeners can afford to purchase mature plants when landscaping their home or planting their flowerbeds. Most of the trees and shrubs sold in garden centers are one-tenth to one-quarter their mature size. This is also true for bedding plants and vegetable transplants. Because the plants are small, there’s a tendency to plant them close together to fill the space as rapidly as possible. The problem is that plants quickly grow together and compete for light. Some of the more vigorous species, especially when planted on the south, begin to shade the slower-growing plants. The better prepared the soil, the quicker the growth.
    Crowded plants are forced to grow tall and spindly with weak stems. The thickness and strength of a plant stem is directly related to the frequency of bending and the number of branches or leaves originating from the stem. Plants that are crowded do not sway with the wind as those that are more exposed. Crowding also prevents side branches and leaves from developing on the stem. As a result, the stem does not increase in diameter and remains weak. Crowding also inhibits flowering.
    Many flowering plants such as azaleas, rhododendrons, roses, crape myrtle, lilacs and Korean dogwoods produce the maximum flowers when planted in full sun. The plants may have been planted in full sun initially, but surrounded with a more vigorous or a taller-growing species, they extend their shade over the slower-growing flowering species. As the flowering plants are exposed to more shade and less sun, their ability to produce flowers is reduced.
    Other species of ornamentals will grow only in full sun. Junipers, Japanese hollies, pine, spruce, fir, arborvitae, chamaecyparis and others deteriorate when planted in shade. As these species are exposed to more and more shade, the plant’s branches die back. Many gardeners associate the dieback with disease and do not realize that the branches are dying from insufficient direct sunlight.
    As the roots of trees grow in diameter, the force that is generated can lift concrete walkways. For planting near walkways or foundations, select trees that will produce deep roots and plant them at a sufficient distance to develop without damaging structures. Trees should never be planted closer than 20 feet from a foundation. I have seen cement block foundations crack and bulge from the pressure exerted by expanding tree roots.
    Before purchasing plants, take time to read the information about each species, select those that best meet your needs, recognize their mature size and make certain that the plants you select will receive the amount of sun they need.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.