Garden Column for the Salisbury Post
Darrell Blackwelder
November 14, 2002

    Just as hormones are important for growth and development of animals, including we humans, they are just as important to plant growth and development. These biochemical compounds are instrumental in controlling the growth and development in all plants. Produced in very small amounts as with animal hormones they are synthesized in one place & take effect in another, often in minute concentrations.
    Plants produce a vast array of hormones with varying functions-too many to list here. Ironically, man has discovered that he can synthesize these chemicals to alter and change plant growth. For example, auxins are growth hormones produced by plant to promote cell growth stem elongation, but may also inhibit growth. Plant scientists have taken this mode of action and developed synthetic herbicides used for controlling lawn weeds. Flower producers often use growth regulators to keep plants dwarf and compact which is a standard practice on bedding plants in early spring. Growth regulators or hormones decrease length on nodes making plants compact, reducing leggy ness producing an attractive marketable plant.
    Commercial landscape maintenance crews often uses growth regulators on clipped hedges to help maintain a fresh clipped appearance during the summer growing season. There even a growth regulator used that eliminates growth of grasses reducing maintenance with string trimmers. Many that maintain high visibility areas incorporate this practice into their maintenance programs.
    Flowering plants, including shrubs such as camellias, roses and azaleas often respond to flowering hormones. Some growth regulators that increase flower size and intensity are called gibberellins. Camellia blooms are often treated with gibberellic acid before flower shows almost doubling the normal size of the blooms.
    Ethylene is the only known gaseous hormone produced by plants. Usually, it inhibits vegetative growth reducing leaf area in drought conditions and accelerates fruit ripening & dropping. Ethylene is released by ripe fruit and is used regularly by commercial food handlers to speed the ripening process of tomatoes, apples and bananas.
    Salicylate, a hormone found in willows and used commercially to produce common aspirin is now recognized as a growth regulator. This old compound is now thought to promote disease resistance and increase flower longevity in some plants.
    Sometimes natures steps in and hormones become unbalanced causing strange things will happen, such as premature bloom. Unusual weather patterns, drought, cold weather, physical damage w alters hormones, especially flowering hormones. A few weeks ago, during October Fest, many plants decided to give us an extra show for the fall. My clematis began to bloom; the neighbor's rhododendron up the street was in full bloom. I noticed a dogwood prematurely blooming at the Historic Hall House. It was evident that hormones were raging, but why now? It seems the plants became bit confused. After a long summer drought, it began to rain again, and it got cooler, then it got warm again. Who wouldn't be confused?
    Unusual weather conditions are probably the culprit to our fall blossom preview. Premature blooming may have an effect on the normal bloom period again in the spring. However, it will not be detrimental to growth and development. What these plants need is something we all need-a normal winter and an average summer. Until then, we will continue to see more confused plants around the county.
    Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com or e mail Darrell_blackwelder@ncsu.edu or phone at 704-633-0571.