The hot, dry weather of June and July this year has provided a rare opportunity to observe the responses of native prairie plants to an extraordinary meteorological event. Having lived through the 1988 drought, it is now becoming clear that the drought of 2012 is rivaling its predecessor in terms of its impact on many plants here in central Wisconsin.
As would be expected, prairie plants with deep taproots are faring best in the drought. Flowers that are weathering the event well include Purple Prairie Clover (Dalea purpurea), White Prairie Clover (Dalea candida), Butterflyweed (Asclepias tuberosa), Pale Purple Coneflower (Echinacea pallida), Wild Petunia (Ruellia humilis), Compassplant (Silphium laciniatum), and Prairie Dock (Silphium terebinthinaceum).
Prairie flowers with waxy leaves that are able to reduce moisture loss are also holding up well. These include Rattlesnake Master (Eryngium yuccifolium), Ohio Spiderwort (Tradescantia ohiensis), Showy Goldenrod (Solidago speciosa) and various species of False Indigos (Baptisia spp.). Many of these plants also have deep roots, which helps them defy the drought. Nevertheless, their ability to conserve moisture within their leaves is a large factor in their success under such demanding conditions.
More shallow rooted prairie flowers and grasses have gone dormant so as to preserve moisture and reduce stress on their perennial root systems. The leaves of some short prairie grasses have rolled up and entered temporary dormancy, and the leaves have actually dried up almost completely. These include grasses such as Little Bluestem (Schizachyrium scoparium), Side Oats Grama (Bouteloua curtipendula), and Prairie Dropseed (Sporobolus heterolepis).
Amazingly, when it eventually rains, or the grasses are watered, their leaves will return to normal within 24 hours! This was one of the things I learned during the drought of 1988 when I assumed that our grass production fields were finished for the year by late June, only to watch in amazement as they came back to life after it finally rained.
Other shallow-rooted prairie species have gone completely dormant and called it quits for 2012. Since they are perennials, they are not dead, only dormant, and should return next year. Their ability to shut down preserves their root systems so they can live to grow another day.
Should I Water My Prairie?
If you seeded a prairie in the spring of 2012 of fall of 2011, it would definitely be beneficial to water it every few days to promote growth of the seedlings that germinated in spring when moisture was available, and to stimulate germination of the remaining seeds in the soil. Many prairie seeds will germinate through the month of July, including most of the warm season prairie grasses and many flowers such as Butterflyweed, Purple Coneflower, Yellow Coneflower, Bergamot, Black Eyed Susan, Purple Prairie Clover, Leadplant, Bergamot, Coreopsis, etc.
Some prairie seeds will often germinate in late summer of early fall, including Lupine, Spiderwort, Prairie Smoke, and Pasque Flower. Maintaining soil moisture in mid to late August can promote germination of these species.
Although most plants in an established prairie can handle moderate drought, the severity of this year’s dry weather is causing severe moisture stress on prairie plants growing on dry rocky and sandy soils. If your prairie is exhibiting signs of drought stress, you can water it to revive the plants. The best approach is to water deeply by running a sprinkler overnight when wind and evaporation are lowest, and electricity demand is also low (to prevent straining the electrical grid during the day when air conditioning demand is high). A good deep watering will help invigorate the prairie plants and supply water into the lower reaches of the soil where they can best utilize it.
You should not have to water your prairie regularly. A good overnight soaking should keep it looking good for a couple of weeks, even without any rain.
If you can’t water your established prairie, or don’t want to water it for ecological or economic reason, or because your pump can’t handle it, don’t worry. These plants have been handling periodic droughts for thousands of years. They know what to do. Even though some plants may be suffering, or have gone dormant, they will return next year after the soil is re-charged with moisture.
Stay cool, and enjoy the amazing prairie plants that can stand up to the heat and drought of the Summer of 2012!