Sudan grass (Sorghum × drummondii) is a rapidly growing, warm-season annual grass. It is utilized as a forage crop, providing high-quality hay and summer grazing, and is also an effective cover crop for soil improvement. Since it is a warm-season species, the success of the stand and the final yield are determined by planting the seed at the correct time. Understanding the plant’s specific temperature requirements is the first step toward a productive growing season.
Identifying the Optimal Planting Window
The most reliable indicator for planting Sudan grass is the temperature of the soil, not the calendar date. This warm-season grass requires a minimum soil temperature of 60 to 65°F (15–18°C) at the standard planting depth for successful germination and vigorous growth. Planting into soil that is cooler than this range significantly delays germination and leads to slow, weak seedling emergence. Seedlings that emerge in cold soil are highly susceptible to chilling injury and various diseases, resulting in a poor stand.
Producers must also ensure that the risk of the last killing frost has passed before planting. Sudan grass has zero tolerance for frost, and cold weather can be detrimental to the young plants. Although the critical soil temperature is the main trigger, waiting until approximately two weeks after the typical corn planting date in your region is a common guideline to meet these minimum heat requirements. Planting during this optimal window ensures the seed benefits from warm, moist soil conditions that promote uniform and fast germination, which helps the plants outcompete early-season weeds.
Planting Strategies for Specific Goals
The intended use of the crop determines how the planting window is managed, even after the minimum temperature requirements have been met. For producers aiming for a single, large harvest of hay or silage, planting should occur at the earliest optimal time, typically late May or early June, to maximize the full growing season. A delayed harvest significantly increases the total biomass yield, though this must be balanced against a slight reduction in forage quality as the plant matures.
When the goal is to provide continuous, high-quality forage for grazing livestock, a sequential or staggered planting strategy is effective. This involves planting smaller plots every two to four weeks throughout the early summer, rather than planting the entire acreage. Staggered planting ensures a continuous supply of young, vegetative grass, which has the highest feed value. The grass is ready for grazing when it reaches 18 to 24 inches in height.
For using Sudan grass as a cover crop, the planting window extends much later into the season. The grass can be planted from early summer through mid-August to accumulate substantial biomass before the first killing frost terminates its growth. This late-season planting is especially useful for scavenging excess soil nutrients and building organic matter. The plant only needs sufficient time to grow and be terminated naturally by cold temperatures.
Regional Timing and Season Length Considerations
Planting dates for Sudan grass vary widely based on the length of the local growing season. In Northern regions, where the frost-free period is shorter, the planting window is compressed, typically starting around late May or early June and closing by late June or early July. Producers must plant early in the season to allow enough time for one or two cuttings of forage before the autumn frost arrives.
Conversely, Southern regions benefit from an earlier start date and a longer growing season, allowing for flexibility in planting. In these areas, the optimal window can open as early as mid-April and remain open until mid-July for forage production. A longer season permits more succession plantings and provides the option to plant as late as August for emergency forage or cover crop purposes. Regardless of location, calculating the time needed for maturity is important, as Sudan grass typically requires about 45 days of growth for each harvest, necessitating at least 90 frost-free days for two cuttings.