Over the past year, the Cooperative Extension office has received a common complaint from homeowners with their inability to germinate warm season grass seed (bermuda, zoysia, centipede). Most of these homeowners were attempting to make repairs or improvements to existing yards, but failed to achieve a stand of grass. While the issue might be common, so is the solution.
There are essentially four components you need to germinate warm season grasses: Patience, Temperature, Soil, & WATER. Warm season grasses require a minimum soil temperature of about 70 degrees Fahrenheit to germinate. However, at this low temperature, seed may take as long as 28 days to germinate. Optimal soil germination temperatures are closer to 86-95 degrees Fahrenheit, which typically do not occur until mid-June through August. For Pamlico County, this means your seeding window is from May through August, with the earlier portion of this period requiring more days to achieve germination.
“Good seed to soil contact” is a phrase that is often used to describe the relationship between germinating seeds and the soil it is growing into. Soil is the media by which plants find water, nutrients, and structure needed for growth. Without immediate access to soil, germinating seeds will quickly dry out or fail to find the nutrients they need to survive. This means you must work to place the seed into direct contact with soil through proper site preparation. If you have a bare area, then light tillage before seeding and raking of seed into the soil will help to level the site and place seed into direct contact. Attempts to overseed warm season grasses into an existing stand of grass is usually unsuccessful. The seed almost never contacts the soil, failing to germinate, or if it does, the small plant quickly dies from lack of water. To achieve the best possible germination success, you should remove all plants and competition from the planting site. This will require removal of existing sod through cultivation and/or non-selective herbicides like glyphosate.
When planning to seed warm season grasses, irrigation is required for success. If you are hoping for mother nature to provide timely rains, you will be disappointed. Seeds must absorb a sufficient amount of water before they will break dormancy. This is the reason we can store seeds for long periods of time. To achieve optimal germination, irrigation should be provided to retain a moist soil depth of about one inch. Earlier in the seeding window this might mean irrigating once or twice per day, but when temperatures get above 85 degrees Fahrenheit, irrigating 4 to 5 times per day could be required. Light sandy soils that dry out quickly need more frequent irrigation compared to heavier, blacker soils. Adding compost or organic matter to the seeded area can help retain moisture for longer periods of time, as well as mulches from wheat straw or commercially available seeding mats. When using mulch do not completely cover seed.
