Plant growth regulators slow vegetative growth in trees, shrubs, and turf, and can be applied through the soil (root uptake) or by foliar application (translaminar uptake). In addition to the obvious benefits of reducing growth rate of plants (maintaining designated spacing and reduced need for pruning), use of growth regulators has been shown to improve plant health overall, by stimulating root growth, improving resistance to drought stress, and increasing tolerance to diseases.
Root Application (trees)
For trees, growth regulators are most commonly employed as a method to control the size and shape of maturing trees while limiting need for physical reduction and reshaping (pruning). When applied properly, regulators can reduce lateral/terminal growth by up to 70%, and the effects of a single treatment will persist for up to 3 years. This permits increasing the pruning interval 3-fold, reduces the trees’ sensitivity to resource availability (including water, soil nutrients, and soil volume), and dramatically increases resistance to stress, pest injury, and physical damage.
Foliar Application (shrubs)
For shrubs, growth regulators are most commonly used to limit terminal growth that compromises the aesthetic appeal of symmetrically pruned or uniform groups of plants, such as boxwood, holly, privet, arborvitae, euonymus, laurel, azalea, and rhododendron. As with trees, proper application of growth regulators can reduce lateral/terminal growth by up to 70%; use of growth regulators on fast-growing shrubs will show results in as little as 2 weeks, and foliar treatments remain effective for 2-3 months. In addition to maintaining consistent shape and form of shrubs and small trees with reduced pruning, growth regulators also improve root health and function, increase chlorophyll production and efficiency (resulting in greener leaves), and can stimulate improved flowering of many ornamental plants.
Broadcast Application (turf)
As with trees, shrubs, bedding plants, and groundcovers, turf grasses and lawns can be strategically treated with growth regulators to reduce leaf-blade elongation, improve consistency of growth, and concentrate chlorophyll production to enhance green color. This results in denser, lower growth and improves resistance to heat stress and drought, reduces the impact of many turf diseases, and builds a stronger root system to tolerate compaction and physical damage.