Dormancy: A Plant's Version of Hibernation

Now that winter has arrived, growth slows or stops for cool and warm-season turfgrasses through most of the United States. As cool-season turfgrass growth slows in the northern regions, and warm-season turfgrasses slow growth in the southern regions they enter into winter dormancy. Dormancy is an important mechanism nature has devised where plants can suspend growth for a period of time in response to unfavorable environmental conditions. Winter dormancy can occur in response to dropping temperatures.

In the above photograph the dormant (brown) turf is zoysiagrass.  The putting green is creeping bentgrass.  Warm-season turfgrasses rapidly enter dormancy once cool temperatures arrive.

Often we associate brown turf with dormancy. However, there are various stages of dormancy that occur. The ultimate stage of dormancy is referred to as true dormancy and is defined as the point where a plant, if exposed to favorable conditions, will not immediately resume growth. The warm-season turfgrasses in their more northern range of adaptation can enter into true dormancy, while cool-season turfgrasses are less likely. Lesser levels of dormancy associated mostly with cool-season turfgrasses are termed resting or quiescence stages. Turfgrasses in a quiescent stage of dormancy quickly resume growth with the onset of favorable growing conditions.

Winter dormancy depends on the existing environmental conditions. In tropical climates like south Florida, bermudagrass may not even enter dormancy. As you move further north toward the transition zone, and colder temperatures - especially important in inducing winter dormancy are cool/cold night temperatures – bermudagrass can reach true dormancy. Under true dormancy even with a rise in temperature above freezing dormancy is not broken.

The above picture is a bermudagrass turf that shows the contrast between a non-overseeded area (dormant) and an area that has been overseeded with perennial ryegrass.

The management advantage of true dormancy for turf managers is it allows for the potential use of non-selective herbicides for winter weed control. Where these herbicides could cause damage to actively growing bermudagrass, they are relatively safe on a bermudagrass turf in true dormancy.

Factors that interact with temperature to induce winter dormancy include light, photoperiod, nutritional levels, and moisture. Light intensity is important primarily in spring for breaking dormancy. High light intensities promote photosynthesis and growth.

Photoperiod or the day length is not fully understood with relation to winter dormancy. It is believed to play a minor role in dormancy but may explain why some cultivars or varieties go dormant sooner than others or resume growth later in the spring.

Management practices like fertilization and watering can promote dormancy. Withholding or reducing nitrogen and water from a bermudagrass turf dormancy can be promoted. These practices might be introduced prior to winter overseeding in an attempt to reduce potential bermudagrass competition.

Minimizing traffic on dormant turf can reduce the potential for injury or death to the turf. Dispersion of wear will reduce any potential injury to the growing point, which will delay growth when conditions become favorable to break dormancy.