Switchgrass, a perennial warm-season grass native to North America, has gained recognition for its versatility in various land management applications. This robust grass is commonly utilized for conservation purposes, creating wildlife habitat, serving as forage for livestock, and increasingly, as a biomass crop for bioenergy production. Successfully establishing a healthy stand of switchgrass requires careful planning and precise execution, given its characteristic slow initial growth rate. This guide provides practical steps for preparing the site, planting the seed, and managing the stand through the critical first year to ensure a productive and long-lasting perennial cover.
Selecting the Right Variety and Preparing the Site
The initial step for successful establishment involves selecting a variety that is well-suited to the local climate and the intended application of the stand. Switchgrass is broadly categorized into two ecotypes: upland and lowland, which differ in their growth characteristics and adaptation. Upland ecotypes are generally shorter, finer-stemmed, and display greater tolerance to cold temperatures, making them the preferred choice for northern climates and drier sites. Lowland ecotypes, conversely, are taller, produce greater biomass, and are better adapted to warmer regions and wetter soils.
Proper site preparation is necessary to give the slow-establishing seedlings a competitive advantage against faster-growing weeds. Soil testing should be performed in advance to determine the soil’s pH and nutrient levels, allowing for amendments like lime, phosphorus, and potassium to be applied according to the test recommendations. Maintaining a soil pH of at least 6.0 is important for optimal nutrient availability and plant health. Pre-planting weed control is important for the success of the stand. Perennial weeds should be suppressed the season before planting using targeted chemical applications.
A firm, smooth, and weed-free seedbed is required, often achieved through tillage followed by rolling, or by using a burndown herbicide application, such as glyphosate, just before planting. Nitrogen fertilizer should be avoided at this stage, as it tends to stimulate weed growth more than the young switchgrass seedlings.
Executing the Planting: Timing and Technique
The timing of planting is related to the seed’s requirement for cold stratification, a process that breaks seed dormancy through exposure to cold, moist conditions. Planting can be done either during the winter (dormant planting) or in the early spring, allowing the natural freeze-thaw cycles of the soil to stratify the seed. For spring planting, the ideal time is when the soil temperature consistently reaches 60 degrees Fahrenheit, typically after the last hard frost.
The seedbed must be firm enough to ensure good seed-to-soil contact and consistent planting depth. Switchgrass seed is smooth and free-flowing, allowing it to be planted using specialized native grass drills, which are the preferred method for precise placement. No-till drills are effective and help conserve soil moisture, but success can be variable depending on the equipment and existing residue.
For smaller areas or if a specialized drill is unavailable, seed can be broadcast onto the soil surface. Broadcasting requires that the area be immediately rolled or cultipacked after seeding to press the seed into the soil. Planting depth is a common factor leading to establishment failure, as the seed must be placed very shallowly. The target planting depth should be between one-quarter and one-half inch, with shallower depths preferred in heavier soils.
Seeding rates are calculated based on Pure Live Seed (PLS), which accounts for the percentage of pure seed that is viable. A common drilled seeding rate for a pure stand of switchgrass ranges from 4 to 6 pounds of PLS per acre. If broadcasting the seed, the rate should be increased to 8 to 10 pounds of PLS per acre to account for less uniform coverage. The specific rate may be adjusted based on the quality of the seed lot and the environmental conditions of the planting site.
Post-Planting Care and First-Year Establishment
Patience is required during the switchgrass establishment process, as the seedlings are slow to emerge and develop during the first growing season. Much of the plant’s initial energy is directed toward developing a deep and extensive root system, which can reach up to 10 feet or more. Above-ground growth will appear sparse and may be overshadowed by weeds. Successful establishment is judged by having one to three switchgrass seedlings per square foot by the end of the first year.
Weed management remains important throughout the first year, as competition is the biggest impediment to stand success. While pre-emergent herbicides are generally not labeled for use on switchgrass, post-emergence herbicides can be used to control broadleaf weeds once the switchgrass seedlings have developed three to four leaves. Weedy grasses are more difficult to control chemically without injuring the young switchgrass plants.
A non-chemical control option involves strategic mowing or clipping of the weeds. This technique should be performed by setting the mower high enough to cut the weeds above the height of the switchgrass seedlings, typically leaving at least a six-inch stubble. Mowing reduces the competition for sunlight and moisture and prevents the weeds from producing mature seeds. The first-year stand should not be subjected to heavy use, grazing, or harvesting. Allowing the plants to establish root reserves without the stress of removal is important for stand longevity and future productivity.