The recent cold temperatures experienced on March 15-16 were enough to cause freeze damage to winter wheat in parts of Kansas. The actual freeze damage will be region-specific, depending on crop growth stage and minimum temperatures (some regions had the worst combination of temperatures and crop growth stage), and, within a region, field-specific, owing to many individual aspects such as crop density, residue level, etc. While there is nothing we can do immediately, growers can prioritize the fields they sample for freeze-damage symptoms based on conditions more likely to result in freeze damage. In this article, we discuss the low temperatures across the state and the individual conditions that might help growers prioritize which fields to sample and which injury symptoms to look for.
How cold did it get?
Cold temperatures across Kansas ranged from -1 degree F in northwest Kansas to 17 degrees in south central Kansas. These cold temperatures spanned the overnight hours of Sunday into Monday morning. The following maps (Figure 1) show the cold temperatures and the duration of time that temperatures were below 12 and 24 degrees. According to the K-State Spring Freeze Injury to Kansas Wheat publication, the approximate injurious temperatures for tillering and jointing wheat are two hours at 12 and 24°F, respectively. These are not hard numbers, as many factors influence freeze injury.
Figure 1. Duration in hours of below freezing temperatures, 12°F (top map) and 24°F (lower map), for March 2 through March 16, 2026. Maps generated by Kansas Mesonet.
Field conditions that can affect the potential for freeze damage
Density of the stand and condition of the plants. If the stand is thick, that will tend to reduce the extent of freeze damage as the warmth of the soil will radiate up into the canopy. On the other hand, well-fertilized succulent wheat has often sustained more freeze injury than wheat that is not as well fertilized. Thin stands are at greater risk of injury because air can penetrate them more easily. If the plants were wet before the freeze, a coating of ice may form, protecting the growing point to some extent. However, if temperatures drop too low, the cold will penetrate the ice.
Residue. No-till fields can often sustain more freeze damage because the residue acts as a blanket, preventing the soil's heat from radiating up into the plant canopy.
Soil moisture. There is often less freeze injury at a given temperature when soils are wet than when they are dry. Wetter soils tend to radiate a little more warmth than dry soils. On the other hand, drought-stressed plants tend to be more tolerant of cold injury, and their lower leaf water content tends to reduce the severity of freeze injury.
Wind speed. Windy conditions during the nighttime hours, when temperatures are at their lowest, will reduce the amount of heat radiating from the soil and increase the risk of injury.
Temperature gradients within the field (position on the landscape). Low spots in the field are almost always the first to have freeze injury. The coldest air tends to settle in the low areas, especially under calm wind conditions.
Wheat variety. Although the sensitivity to freezing temperatures at a given growth stage is very similar across all varieties, Kansas wheat varieties can differ in their release from winter dormancy by up to 3 weeks. Because of differences in winter-dormancy release, late-release varieties may escape freeze injury due to delayed development.
Injury symptoms to look for in the coming days
There are many possible scenarios after a freeze, and producers should not make any immediate decisions. 10 to 14 days of warm temperatures are needed to allow the wheat to resume growth and to properly assess freeze damage to the wheat crop, which will depend strongly on the crop stage (Figure 2).
Figure 2. Estimated wheat growth stage on March 16 based on growing degree day accumulation in Kansas. Map generated by Kansas Mesonet.
Greenup
Wheat that hasn’t started to joint yet (Feekes 3: completion of tillering through 5: Leaf sheaths strongly erect) will likely show damage to the existing foliage. This wheat will have damage that causes the leaves to appear dark green to blackish, and it will turn brown and crispy (Figure 3).
Figure 3. Leaf damage from cold temperatures. Dark green to black coloration of leaves following exposure to temperatures below 10 degrees F (left). Leaf burn from freeze damage (Right). By itself, this is cosmetic damage only. Photos by Jeanne Falk Jones and Romulo Lollato, K-State Extension.
Splitting the wheat stem to identify the growing point and determine whether it is above or below the soil surface can help assess the risk of freeze injury. It is also important to note that the growing point location differs between the primary tiller and later-developing tillers.
Jointing
Where wheat was at the jointing stage, producers should evaluate their fields 10-14 days after the freeze event for the following:
- The color of newly emerging leaves. If they are nice and green, that probably indicates the tiller is alive. If newly emerging leaves are yellow, that likely indicates the tiller is damaged from the freezing temperatures. The color of existing leaves is not terribly important, except for the flag leaf, which should not have emerged at this point yet. Existing leaves will almost always turn bluish-black after a hard freeze, giving off a silage odor. Those leaves are burned back and dead, but that in itself is not a problem as long as newly emerging leaves are green.
- The color of the developing head or growing point in wheat that has jointed. As long as heads are light green, crisp, and turgid, the head in that tiller is fine. If the head is whitish, flaccid, and mushy, it has died (Figure 4).
- Ice in the stems. If there was ice in the stems below the first node the morning of the freeze, those tillers may be damaged (although not always) and may not produce grain. You may see split stems from ice accumulation.
- Stem integrity. If the wheat lodged immediately after the freeze, that indicates stem damage. Later tillers may eventually cover the damaged tillers. Even if there is no immediate lodging, look for dark lesions or crimps anywhere on the stems. If these symptoms are present, it usually means the wheat will lodge at some point during the season. If the stems look undamaged, that’s a good sign.
Figure 4. Following an early freeze, crops at jointing might still develop healthy heads (left panel). However, depending on minimum temperatures and duration of the freeze event, the developing head might be killed even if still within the stem (right panel). The dead head is whitish and flaccid, while the healthy head is light green and turgid. Photos by Romulo Lollato, K-State Extension.
For the first few days, producers should walk the fields to observe lodging, crimped stems, and damaged leaves. They should not take any immediate action in response to the freeze, such as destroying the field for re-cropping. It will take several days of warm weather to assess the extent of the damage accurately. After several days, producers should split open some stems and check the developing head.
Where the freeze killed stems and/or growing points, new tiller growth (coming from the crown area) will occur (Figure 5). In many cases, new tiller growth can be observed even when the stems do not show any symptoms of freeze damage for some time. In those cases, the first sign that the tillers are dead is the sudden growth of new tillers at the base of the plant.
If secondary tillers may begin growing normally and fill out the stand, the wheat may look ragged because the main tillers are absent. Producers should scout for bird cherry oat aphids and other potential insect or disease problems on these late-developing tillers. If both the main and secondary tillers are injured, the field may eventually have large areas that have a yellowish cast and reduced yield potential.
Figure 5. Left: A stem that was split open by having ice form within the stem. This stem has died, and a new tiller has begun to grow at the base. Right: Some of the tillers on this plant had freeze damage to the lower stems. These stems are dying, but the symptoms may not be immediately evident. The growth of new tillers from the base of the plant is a sure sign that the main tillers are dead or dying. Note the brown lesion on the stem with the two new tillers. Photos by Jim Shroyer, professor emeritus, K-State Extension.
Boot
As we look ahead to potential future freezes the Kansas wheat crop could experience, at the boot stage, wheat can be injured if temperatures drop into the mid- to upper 20s for several hours. Injury is more likely when it occurs repeatedly and when it is windy at night. To detect injury, producers should wait several days, split open some stems, and look at the developing head. If the head is green or light greenish in color and seems firm, it will most likely be fine. If the head is yellowish and mushy, that’s a sign of freeze injury.
Freeze injury at the boot stage causes several symptoms when the heads are enclosed within the flag-leaf sheaths. Freezing may trap the spikes inside the boots, preventing them from emerging normally. When this happens, the spikes will remain in the boots, split out the sides of the boots, or emerge base-first from the boots.
Sometimes heads emerge normally from the boots after freezing but remain yellow or even white instead of their usual green color. When this happens, all or part of the heads have been killed. Frequently, only the male parts (anthers) of the flowers die because they are more sensitive to low temperatures than the female parts. Since wheat is self-pollinated, sterility caused by freeze injury results in poor kernel set and low grain yield.
It’s possible for some of the spikelets to be alive and a healthy dark green while other spikelets on the same head are damaged. If a spikelet flowers normally and the kernels on that spikelet develop normally, then the head is at least partially viable and will produce grain (unless it freezes again, of course).
More information on freeze damage to wheat is available in Spring Freeze Injury to Kansas Wheat, K-State Research and Extension publication C646, available at: http://www.ksre.ksu.edu/bookstore/pubs/C646.pdf.
Logan Simon, Southwest Area Agronomist
lsimon@ksu.edu
Jeanne Falk Jones, Northwest Area Agronomist
jfalkjones@ksu.edu
Tina Sullivan, Northeast Area Agronomist
tsullivan@ksu.edu
Romulo Lollato, Wheat and Forages Specialist
lollato@ksu.edu
Tags: wheat freeze injury