Stage 3: Growing Point Differentiation (GPD)
The plant is entering a rapid period of growth. The growing point can be found just above the ground by splitting the stalk, and the number of seeds per head will be determined over the next couple of weeks. This stage typically occurs 30 to 40 days after emergence, when the plant is 12 to 15 inches tall.
At this stage, one or two of the bottom leaves may have fallen off, and tillers may be present at the base of the plant. Prior to GPD, the plant can withstand considerable stress with minimum effect on yield. However, stress during GPD can affect the potential number of seeds per head at flowering. Stage 3 is a key time to apply irrigation if soil moisture conditions are dry and irrigation is available.
Photo Source: C. Trostle, Texas AgriLife