Before the 1940s, most grain sorghums were 5-7 feet tall, which created harvesting problems. Today, sorghums have either two or three dwarfing genes in them, and are 2-4 feet tall. While there are several grain sorghum groups, most current grain sorghum hybrids have been developed by crossing Milo with Kafir. Other groups include Hegari, Feterita, Durra, Shallu, and Kaoliang. The grain sorghum head is a panicle, with spikelets in pairs.
Sorghums are normally self-fertilized, but can cross pollinate.
Hybrid sorghum seed is produced utilizing cytoplasmic male sterility. Sorghum flowers begin to open and pollinate soon after the panicle has completely emerged from the boot. Pollen shedding begins at the top of the panicle and progresses downward for 6-9 days. Sorghum can branch from upper stalk nodes. If drought and heat damage the main panicle, branches can bear panicles and produce grain.