“The answer to that is yes, the very warm temperatures we’ve experienced recently can cause wheat to break dormancy and green up early, especially where moisture conditions are adequate. This isn’t welcome news right now, because you never want to force the plants to start growing too early, but it’s too early to say whether it will cause major problems,” Shroyer said.
When wheat breaks dormancy and becomes physiologically active during late winter, it can regain some level of winter hardiness if temperatures get colder again gradually, he added.
Sublette, Kansas, U.S., set three days of record high minimum temperatures Feb. 14 through 16, according to State Climatologist Mary Knapp.
“Three in a row will break dormancy,” she said, noting that Sublette’s temperature did not dip below 68 degrees F on the 16th, smashing the previous minimum of 44 degrees F set in 1961.
“The best case scenario is that there are just one or two days of unusually warm temperatures, then a gradual drop perhaps back into the 20’s and 30’s over the following week. Most wheat varieties grown in Kansas can easily regain enough winter hardiness to survive these conditions,” Shroyer said.
The worst case scenario is when a period of unusually warm weather is followed by a drop into the low teens or below in just one day, as happened in 1989, he explained. Some varieties may be unable to withstand a sudden return to bitterly cold temperatures.
Another consideration is the condition of the plants when they green up, and whether they can afford to become physiologically active at this time, he said.
“In some areas, especially western Kansas, many wheat plants are small with poorly developed root systems due to the continuing drought in that region. If these plants with no roots start growing during these periods of warm temperatures while the topsoil is still very dry, they could quickly run out of water,” he said.
This will stress the young plants and possibly cause some loss of stand, especially if high winds cause an even greater increase in evapotranspiration rates. Injury from blowing soil where stands are thin could also stress the plants.
“In short, wheat plants with little or no root system right now are at a somewhat higher level of risk after breaking dormancy last week than plants with a good, healthy secondary root system. This risk includes winterkill, drought stress injury or desiccation, and physical injury from blowing soil,” he said.