It may not feel like it sometimes, but talk to most weather forecasters, and they will say winters have been warming faster than any other season of the year.

So, what effect can this have on winter wheat? That depends.

Dennis Pennington, wheat systems specialist with Michigan State University Extension, says nothing contributes more to winter wheat production than planting date in fall.

“The tiller phase starts once the first true leaves have fully emerged and lasts until the beginning of stem elongation in the spring,” he says. “Tillers produce nodal roots, which contribute to water and nutrient uptake.

“Planting date has the largest influence on tiller development period. Temperatures in the fall, winter and early spring play a role, but not nearly as much as planting date. You will never accumulate enough extra [growing degree days], even in an abnormally warm fall and winter, to offset the time lost due to late planting.”

But cold weather, or even lack thereof, can still have an effect.

Wheat needs the cold

Winter wheat goes through two processes crucial for winter survival and production next spring.  

The first, vernalization, is the “cooling off” period wheat plants must go through to reach reproduction — or produce seed. Vernalization requires a six- to eight-week period of temperatures below 48 degrees F. Without that chill, wheat will remain in the vegetative stage and never produce seed.

The second, hardening off, affects plants’ cold tolerance. Hardening off begins once the temperature of the crown, or growing point, dips below 48 degrees. Water in certain tissues is replaced by more dense carbohydrates that are less prone to freezing. Winterkill occurs if the water in the crown freezes.

When water freezes, it expands, rupturing cell walls that can permanently damage the crown. If this is severe enough, the plant can die. 

What if it gets warm too early?

Pennington says wheat tillers typically break dormancy once soil temperatures rise above 40 degrees, with full growth once soil temperatures reach the upper 40s.

There is a risk that plants can be affected if it gets too warm too early, and then a late frost, or freeze, occurs. But it all depends on location and the growth stage of the wheat, he says. For example, in his location in Michigan, this is less likely to happen.

“In our latitude, the last killing frost in the spring usually occurs at earlier growth stages, typically prior to Feekes 6 or 7,” Pennington says. “Feekes 6 is the growth stage where the growing point moves above the soil surface and sits at the top of the first node. Yield loss occurs when water or solutes in the growing point freeze and rupture cell walls. At Feekes 6 or even 7, the growing point is close to the soil surface, which provides some buffering effect of frost.

“In Southern latitudes, such as Kentucky, the last killing frost can occur at later growth stages when the growing point is further from the soil surface. Killing frost at those growth stages can have a significant impact on yield potential.”

Click here for an interactive wheat staging graphic.

What if wheat growth is too good?

This is where good management will come into play next spring. Think about splitting your nitrogen application or applying a growth regulator to ensure the crop won’t lodge before harvest.

Pennington explains: “Wheat that tillers out well and achieves a significant amount of growth in the fall will need to be managed properly. Wheat with five to seven fall tillers usually has a thicker canopy, which can be a haven for disease or insects. Growers should scout their wheat this fall, or early spring, assess the number of tillers and how much vegetative growth they have. If the canopy has closed and it is hard to see the rows, pay special attention to those fields in the spring. Watch for powdery mildew and aphids, in particular. 

“Thick, early growth increases plant-to-plant competition, causing plants to grow taller more rapidly, which increases the risk of lodging,” he adds. “In those advanced fields, delay nitrogen application until Feekes 5, where the pseudostems become more erect and upright. You may want to consider split application, putting 60% of your nitrogen at Feekes 5 and the remaining 40% by Feekes 6.5 to 7.

“If disease or insect thresholds are met, apply fungicide and/or insecticide. Good fall growth creates high yield potential. Managing to protect that potential will be important in the spring.”