Common Bermuda grass (Cynodon dactylon) is the only species that is grown from seed; all other hybrids and species of Bermuda grass fail to produce seed and are started from sprigs or stem segments. Bermuda grass is a warm-season grass that grows only when soil and air temperatures are warm enough. Young seedlings must grow sufficiently in size to survive any cool or wet weather that occurs during the winter dormancy period. Bermuda grass is grown across U.S. Department of Agriculture hardiness zones 7 and warmer.
Seeding Time Frame
Texas A&M University notes that Bermuda grass seed is best sown when soil temperatures are above 65 degrees Fahrenheit. Too cool soil temperatures retard seedling development and/or extends the length of time necessary for roots to establish and support further plant growth. Soil temperatures of 68 degrees F to 75 degrees F are ideal and, according to Seedland, sowing is appropriately done from late spring to late summer. Pike Nurseries of Atlanta more specifically state "from mid-May to mid-August."
In the United States, the general rule is to not sow Bermuda grass seed past mid-August. In more northern areas, the seed needs at least 90 days before the first expected fall frost date to grow and establish; in warmer southern regions this time is reduced to 60 days prior to frost. In warm winter regions like Southern California and southern Florida, seeding occurs year-round if soil temperatures are above 65 degrees F.
Insufficient time before a fall frost on newly sprouting Bermuda grass results in plant death. Germinating seeds nipped by frost or subfreezing temps are fully killed. Young plants with small root systems and few leaves do not survive well since they have little food-making abilities or resilience to frosty temperatures. When Bermuda grass is dormant during cold weather months, above-ground leaves or stems may die back, but it rejuvenates from its healthy underground rhizome roots in spring.
Seedland mentions that if it is absolutely necessary to sow Bermuda grass seed in autumn or winter when soil and air temperatures are too chilly, dormant seeding is a option, albeit risky. Temperatures must not rise above 60 to 65 degrees F when fall and winter frosts or freezes may occur. The risk with laying Bermuda seed in cool weather is that any warm spells causes germination. Once nighttime temperatures drop to freezing, these seedlings are killed.
Seedland and Pike Nurseries mentions that Bermuda grass will establish and thus survive a winter of frosts and mild freezing temperatures if 60 to 90 days of active growth occurs after seed germination. Proper site preparation, irrigation of seedlings, environmental warmth, and correct timing and dosages of nitrogen-rich fertilizers helps Bermuda grass seed establish. As long as seed grows with adequate time before the initial onset of frost, the lawn will overwinter and continue to grow the following spring once it warms up adequately.