Because sorghum is self-fertile, a large plot is not needed for pollination purposes. Mix a balanced fertilizer into the bed or row before planting.
Choose a site that gets full sun, at least 6 hours of direct sunlight a day, and it’s best to stick to the edge of your gardens. Sorgham can get very tall and shade other crops you might not want shaded.
Sorghum needs soil temperature to reach at least 60°F, and does best seeded directly in the garden rather than in pots inside to start. Plant sorghum by hand, ½-1 inches deep, in clumps of four seeds per hole. Space the holes 18 to 24 inches apart. Four seeds should yield about three uniform stalks and heads, enough to make a few dried arrangements if you’re growing them for ornamental use.
For grain production, plant one seed every 4 inches on 30-inch spaced rows. An average head of sorghum will yield about one-tenth of a pound of grain.
Harvesting all three varieties is fairly simple and similar. For sweet sorghum, cut the canes at ground level about two weeks after the milk stage. Next, strip off the leaves and ground or press the canes, which will yield a light green juice that can then be cooked into sorghum syrup. At this stage, the seeds aren’t yet fully mature, but they can be used as animal feed, or cooked and eaten like other whole grains.
Grain and sorghum are harvested after the seeds fully mature. The hard, glossy seeds of grain sorghum are harvested by cutting them off with a small portion of the stalk attached. Dry them in a warm, well-ventilated place for at least a week, then roll the dried seed heads on a hardware cloth screen or soil sieve to free the seeds and separate them from plant debris. Your processed harvest can then be stored.
As for broom varieties, when seeds are mature, cut the stalks as long as you need them for floral arrangements or crafts. Allow the stalks to dry in small bunches.
Sorghum, Sorghum bicolor
Pollination, self/wind; Life Cycle, annual; Isolation Distance, 200 feet
Perfect, self-pollinating flowers are held in panicles (flower heads), which dry on the plant for easy harvest. Wind pollination is possible with very open flowers, though rare. Dry panicles can be cut individually as they are ready, and screened and winnowed to clean for storage.