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Field Crops, Grains & OilseedsSorghum-Sudan Planting Calendar
Sorghum-sudangrass is a heat-loving summer annual, so the planting calendar is set by warm soil rather than the first nice day in spring.
Key points
- Plant sorghum-sudangrass after soils warm well past the last spring frost, not on a fixed date.
- Confirm the soil temperature threshold with your state extension guide.
- Late plantings lose yield and risk frost, so count weeks backward from your first fall frost.
- Prussic acid is a livestock risk after frost or drought stress, so ask extension and your veterinarian.
- Keep records to tune the timing field by field.
When should you plant sorghum-sudangrass?
Sorghum-sudangrass germinates poorly in cold soil, and extension guides from Utah State, Kansas State, Georgia and Nebraska all tie planting to soil warming well after the last spring frost. Planting early into cool ground risks a thin, slow stand that weeds can overtake.
Look at your average last spring frost date, then wait until soil is consistently warm. Many extension guides give a soil temperature threshold for the crop; check the one from your state, since recommendations differ by region and variety.
Seed size and depth matter as well. Planting into moist soil at a shallow, even depth helps seedlings emerge together, and a firm seedbed helps seed make good contact with moisture.
How do you check soil temperature properly?
Take readings in the morning at seeding depth over several days, not just one afternoon. A single warm afternoon can be misleading if cold nights follow.
Keep a simple record of each field. South-facing slopes and sandy soils warm earlier than low, wet ground. Planting in order of warmth lets you stagger harvest as well.
If you have no soil thermometer, your county extension office or a state weather network may publish local soil temperatures that you can use as a rough guide for your area.
- Measure at seeding depth, in the morning
- Look for a steady trend over several days
- Plant the warmest fields first
- Confirm the crop's temperature threshold with your state guide
How late can you plant it?
Because it grows fast in heat, sorghum-sudangrass is often used as a late planted emergency or double-crop forage. An Ohio State newsletter on July plantings of warm-season annual grasses discusses how late seeding reduces total yield and raises questions about frost before the crop is used.
Work backward from your average first fall frost and the number of weeks the crop needs before your first cutting or grazing. If the math is tight, consider a different crop. Your state extension office can suggest options.
Consider how the crop fits your other work. A late planting after a small grain harvest can use a field that would otherwise sit idle, but only if you have the moisture to get it started.
When can you graze or cut it?
Sorghum-sudangrass can accumulate prussic acid after frost or during drought stress, which is a livestock safety issue. Extension publications describe waiting until plants reach a certain height before grazing and avoiding grazing right after a frost.
Because this is an animal health matter, follow the guidance from your state extension specialist and your veterinarian rather than a general rule of thumb. Ask specifically about regrowth after cutting or grazing and about stress periods.
Ask whether a hay or silage harvest suits you better than grazing, since cutting height and regrowth timing are handled differently and your extension specialist can explain the options.
What does it do to the next crop?
The crop produces a lot of biomass and can tie up soil nitrogen as residue breaks down. It is also used as a cover crop for weed suppression and compaction relief, as described in federal conservation fact sheets.
Plan the following crop with that residue in mind. Use a soil test and local recommendations for nitrogen, since nutrient management rules vary by state.
Residue from this crop can be heavy, so check how your planter or drill handles it before the next planting season, and adjust your tillage or no-till plan accordingly.
What should you write down?
Record planting date, soil temperature, stand quality, first harvest or grazing date and total number of cuttings. Add notes on weather stress.
These notes show whether your calendar is too early, too late or about right, and they help when you decide between sorghum-sudangrass and another summer annual next year.
Also note how weeds behaved in the stand. A dense, fast canopy often suppresses later weeds, which is useful information when you plan the next field. Add a line on what you would change next year, such as planting a week later or increasing the time between cuttings, so the lesson is easy to find.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.