Sorghum-Sudangrass as a Cover Crop
Grass cover crop
Sorghum-sudangrass is a fast-growing, warm-season annual grass that is a cross between grain sorghum and sudangrass. It is one of the most productive summer cover crops available to gardeners and small farmers, valued for the large amount of biomass it puts on in a short window. It is a common choice for filling a summer gap between spring and fall crops.
Benefits
Sorghum-sudangrass produces a heavy volume of top growth and a deep, fibrous root system, which together add a large amount of organic matter to the soil. Those aggressive roots help break up compacted layers and improve soil structure and water infiltration. The tall, dense canopy shades the ground and suppresses many summer weeds, while the fibrous roots hold soil in place and reduce erosion during heavy summer rains. As a grass, it is not a nitrogen fixer, so it is often paired with a summer legume when adding nitrogen is also a goal.
When to plant
Plant sorghum-sudangrass in late spring or summer once the soil has warmed and the danger of frost has passed, since it needs heat to grow well. It is typically drilled or broadcast into a prepared seedbed and lightly covered, and firm seed-to-soil contact helps with even emergence. Your local Cooperative Extension office can give you general seeding ranges and timing that fit your region.
Growing it
It grows very quickly in warm weather and can reach several feet tall within a matter of weeks under good moisture and heat. Many growers mow it once it reaches roughly three to four feet to encourage thicker stands, stronger root growth, and more tillering, which increases the total organic matter it returns to the soil. It is fairly drought tolerant once established but responds strongly to summer heat and adequate moisture.
Ending the cover crop
Sorghum-sudangrass is a warm-season annual, so it will winterkill on its own once temperatures drop in fall in most regions. To end it earlier, you can mow or cut it and then turn the residue into the soil, though the coarse, high-carbon stalks break down more easily if they are chopped or mowed first. A roller-crimper can also be used to knock it down and lay a mulch mat when it reaches the flowering stage. Because the residue is bulky and slow to decompose, allow time for it to break down before planting a following crop.
Best for
It is best for gardeners and small farmers who want to build organic matter quickly, smother summer weeds, or loosen compacted soil during a warm-season fallow period. It suits anyone with an open summer window who can plant into warm soil and wants maximum biomass in a short time.
General guidance for US growers. Seeding rates and regional mixes vary; your local Cooperative Extension office and NRCS can help you plan. Page updated Aug 4, 2026.