Hormone therapy for plants

By Darrell Blackwelder

For the Salisbury Post

Just as hormones are important for growth and development of humans, they are also important for plant growth and development.

Plants contain these and other biochemical compounds that are instrumental in many stages of growth and development of plants. Produced in very small amounts, plant hormones are synthesized in very minute concentrations.

Plants produce a vast array of hormones with varying functions — too many to list here. Plant scientists have discovered they can synthesize these chemicals to alter plant growth. For example, auxins are growth hormones produced by plants to promote cell growth and stem elongation, but they may also inhibit growth.

Plant scientists have taken this mode of action and developed synthetic herbicides used for controlling lawn weeds.

Some greenhouse producers implement synthetic growth regulators to keep bedding plants dwarf and compact in early spring. Growth regulators or hormones decrease length on nodes, making plants compact, reducing leggy growth and producing an attractive, marketable plant.

Landscape maintenance companies often use growth regulators on clipped hedges to help maintain a fresh clipped appearance during the summer growing season while reducing rapid growth.

There’s 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 and 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 enthusiasts who treat buds with gibberellic acid before flowering often 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 and 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 nature throws us a curve and hormones become unbalanced, causing strange things to happen, such as premature bloom. Unusual weather patterns, drought, cold weather, physical damage all alter plant hormones, especially flowering hormones. Unseasonable weather is usually 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.