Amanda de Oliveira Silva, Small Grains Extension Specialist

First hollow stem (FHS) occurs just prior to jointing and is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of hollow stem below the developing grain head (Fig.1). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

Several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). Varieties can differ by as much as three weeks in onset of first hollow stem, and later maturity varieties generally reach first hollow stem later. Dual-purpose producers are encouraged to select varieties that are characterized as medium, late or very late in occurrence of FHS.

The latest FHS results for each variety planted in our forage trial at Stillwater are listed below (Table 1). A few varieties are at FHS (values at or above 1.5 cm), but values are likely to move slowly with current cold conditions in Oklahoma.

The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis.

Methods for scouting for FHS:

• Check for FHS in a non-grazed area of the same variety and planting date. Variety can affect FHS date by as much as three weeks and planting date can affect it even more.
• Dig or pull up a few plants and split the largest tiller longitudinally (lengthways) and measure the amount of hollow stem present below the developing grain head. You must dig plants because the developing grain head may still be below the soil surface at this stage.
• If there is 1.5 cm (~5/8″) of hollow stem present, it is time to remove cattle.

Table 1. First hollow stem results for each variety collected at Stillwater on 02/06/21. Plots were planted on 09/21/21. The threshold target for FHS is 1.5 cm. The value of hollow stem for each variety represents the average of ten measurements.

Similar to previous years, we will monitor occurrence of FHS in our wheat plots at Stillwater and Chickasha and report the findings on this blog.

• Additional resources available:
• PSS-2147 First Hollow Stem: A Critical Wheat Growth Stage for Dual-Purpose Producers.
• CR-2141 Fall forage production and first hollow stem date in small grain varieties during the 2019-2020 crop year