Sorghum is planted in spring once soil temperatures reach 60°F at planting depth, typically from mid-May through early June across most of the U.S. Growing Belt. Getting the timing right matters more with sorghum than many other grain crops because its tropical origins make it especially sensitive to cold soil and late frosts.
Soil Temperature Is the Key Trigger
The single most important number for sorghum planting is soil temperature. While corn and soybeans can go in the ground at 50°F, sorghum needs the soil to be consistently at or above 60°F, measured at about 1.5 to 2 inches deep. Some sources cite a range of 55 to 60°F as the minimum for germination, but the standard recommendation from extension programs in major sorghum states is to wait for 60°F. Planting into cooler soil leads to slow, uneven germination and weak stands.
“Consistently” is the key word. A single warm afternoon doesn’t count. You want soil temperatures staying above that threshold for several days in a row, including overnight, before committing seed to the ground. Many state extension services publish real-time soil temperature maps you can check daily during planting season.
Planting Windows by Region
Calendar dates vary widely depending on where you are, but here’s a general framework for grain sorghum in the United States:
- Southern Plains and Deep South (Texas, Georgia, southern Oklahoma): Late March through April in the southernmost areas, moving into May farther north. Soil warms earlier here, so 60°F arrives sooner.
- Central Plains (Kansas, central Oklahoma, Nebraska): Mid-May through early June is the primary window. In northern Kansas and Nebraska, planting typically starts in late May.
- Western states (California’s Central Valley): Once soil temperatures hold above 60°F and freeze risk has passed, generally April through May depending on elevation.
The best yields in Kansas, the top sorghum-producing state, come from plantings made in May and early June. Earlier planting within that window gives the crop more time to develop tillers (secondary stems that each produce their own grain head), which stabilizes yield even if conditions turn stressful later in the season. Planting in late June or July produces fewer tillers and less stable yields.
Frost Risk and Early Planting
Sorghum seedlings have almost no frost tolerance. Research on seedling freezing thresholds found that significant injury begins at temperatures just below freezing, around 29 to 30°F, and damage increases sharply below that point. Even brief exposure to a light frost can kill young sorghum plants outright.
This creates a tension for growers: planting early improves yield potential, but sorghum seed planted in April across the Great Plains can encounter frost events in late April or early May. The practical solution is to time planting so emergence happens after the last expected frost date for your area. Since sorghum typically takes 7 to 10 days to emerge, count backward from your last frost date to find your earliest safe planting window. If your last frost date is May 10, for example, planting in late April could work, but you’re accepting some risk.
How Deep to Plant
Sorghum seed is small compared to corn or soybeans, so proper depth matters more than you might expect. The recommended planting depth is 1 to 2 inches, with 1.5 inches being the sweet spot for most conditions. The goal is to place the seed where it has at least a quarter inch of moist soil above it for good seed-to-soil contact.
In dry conditions, you may need to plant slightly deeper to reach moisture, but going beyond 2 inches makes emergence difficult. A Kansas State University planting depth study found that shallow placement at half an inch and deep placement at 3 inches both performed worse than the 1.5-inch target. If the top 2 inches of soil are bone dry and there’s no rain in the forecast, it’s generally better to wait than to chase moisture at excessive depth.
Grain Sorghum vs. Forage Sorghum
The 60°F soil temperature rule applies to both grain and forage types. The main timing difference comes down to maturity. Grain sorghum varieties range from early to late maturing, and choosing the right maturity for your planting date is critical. If you’re planting on time in May, a medium or full-season hybrid works well. If you’re planting late, switch to a shorter-season variety so the crop can mature before fall frost.
Forage sorghum follows the same planting window, but photoperiod-sensitive forage varieties behave differently. These types won’t flower until very late in the season (late November in most of the U.S.), which keeps them in a vegetative state all summer, producing maximum leaf and stem biomass. That’s by design for silage or hay, but it means they need to be harvested before a killing frost rather than left to mature grain.
Double Cropping After Wheat
Sorghum works as a double crop planted after wheat harvest, but this is a higher-risk strategy. Wheat comes off the field in June or early July in most of the Plains, leaving a short growing season for the sorghum to mature before fall frost. Hot, dry conditions in July and August can stress germination and grain fill.
If you’re double cropping, choose an early-maturing sorghum hybrid. Medium-late or late varieties simply won’t have enough heat units to finish before the season ends. Late-planted sorghum also tillers less, so bump up your seeding rate slightly and consider narrower row spacing to compensate. Weed pressure from warm-season grasses like crabgrass tends to be more aggressive in double-crop situations, so a solid pre-emergence herbicide plan is important.
What Happens When You Plant Too Late
Every week of delay past the optimal window chips away at yield potential. Late-planted sorghum faces more heat stress during its critical flowering and grain-fill periods, produces fewer productive tillers, and has a narrower margin before fall frost. In the central Plains, the cutoff for reasonable grain sorghum yields is roughly mid-June in the northern regions, late June in the south-central areas, and into July only in eastern Kansas where the growing season is longer.
If you’ve missed your ideal window, the most effective adjustment is switching to a shorter-season hybrid. A variety that matures 10 to 15 days earlier than your standard pick can make up for lost time and still finish before frost. Pairing that with slightly higher seeding rates helps offset the reduced tillering that comes with late planting.