Fall growth and development of wheat
This month is a good time to take a close look at your wheat, and see how well it has developed so far. Wheat needs at least 4-5 leaves and 1-2 tillers prior to winter dormancy for maximum cold tolerance. Wheat that has fewer tillers and leaves will be more susceptible to winter kill (Figure 1).
Figure 1. Differences in wheat growth and development as affected by planting date. Wheat planted late October showing no primary tillers, while wheat planted early October has started to tiller. Both crops still need significant fall growth to properly prepare for winter dormancy. Photo taken at the North Agronomy Farm, Manhattan, KS, by Romulo Lollato, K-State Research and Extension.
It is important to look not only at the topgrowth, but at the root system development as well (Figure 2). Roots coming out from the seed are called seminal roots and are used to take up water and nutrients throughout the whole growing season. There aren’t very many of these roots so their contribution to overall wheat water and nutrient uptake is limited.
The two protrusions coming out of the white area about an inch above the seed in the photo of early-October planting in Figure 2 are crown roots. These roots take up most of the water and nutrients the plant will need, and they are very important for the plant to survive the winter. If a cow were grazing on this wheat, though, she would probably pull the plant out of the ground as she is eating the leaves as there aren’t many roots holding the plant in the soil yet. This wheat crop still needs considerable fall growth prior to grazing or winter dormancy.
Figure 2. Wheat seminal and crown roots development as affected by planting date. Both rooting systems are not well enough developed to be grazed, and may be susceptible to nutrient deficiencies or desiccation damage over the winter if the crown roots do not get more developed. Photos taken at the North Agronomy Farm, Manhattan, by Romulo Lollato, K-State Research and Extension.
The photos below illustrate various degrees of growth and development, and what you’d like to see when you examine your wheat this fall.
Figure 3. Wheat fall growth and development as affected by planting date. As expected, there is better canopy coverage with early-planted wheat for dual purpose (mid-September planting) as compared to wheat planted at the optimal planting time for grain only (mid-October planting). This does not necessarily mean the early-planted wheat is in better condition for winter, however. As long as the wheat planted in mid-October has 1-2 tillers and good crown root development (as in Figure 4B below), the plants will have adequate growth going into winter. In addition to having adequate topgrowth and root development, factors such as the extent of the plants' cold hardening, variety differences in winterhardiness, soil moisture and temperature, and snow or plant residue protection on the soil surface will ultimately have an impact on winter survival. Photos by Romulo Lollato, K-State Wheat Extension Specialist.
Figure 4. (A) Some of the crown roots are over an inch long. If the weather is mild for a couple more weeks, the roots should grow even more, which would be desirable. (B) Ideal wheat above and below ground development before winter dormancy, with crown roots fully developed and able to provide water and nutrients to the plant. With this amount of crown root development, wheat plants should be well anchored so that if cattle were grazing the wheat they couldn’t pull the plants out of the ground. Photos by Jim Shroyer, professor emeritus, K-State Research and Extension.
Romulo Lollato, Wheat and Forages Specialist