By Gil Landry
University of Georgia
Keeping your lawn vibrant and green year-round may take more
than
one grass. And you can have just that by overseeding your
warm-season grass with a cool-season variety.
For successful overseeding, you need to:
* Choose the proper seed.
* Properly prepare for and time the overseeding.
* Carefully maintain the overseeded grass.
* And attentively manage the spring transition back to the
warm-season grass.
You also need to maintain a healthy warm-season turf all year.
It’s particularly important to keep the soil fertile, relieve
soil compaction and prevent excessive thatch.
The best for your needs
The proper seed is the grass with the characteristics best
suited
to your particular needs. Annual ryegrass has fast been replaced
by perennial ryegrasses because of their improved quality, stress
and pest tolerance and manageability.
Overseeding rates in lawns range between 5 and 10 pounds per
1,000 square feet. Use high-quality, “Certified” (blue tag) seed
that’s free of annual bluegrass (Poa annua) to maintain
weed-free
turf.
Use seed treated with fungicides, too, such as Apron or Koban.
This is particularly true for early fall, since seedling blight
diseases can be a problem at this time.
10 pound fast, 5 pound thin
The 10-pound rate provides a fast stand for fall use. The
5-pound
rate provides a thinner stand that doesn’t provide much coverage
until spring.
The right seeding rate depends on how you want it to look and
how
much traffic the turf will bear. Higher-traffic areas need higher
seeding rates. However, higher seeding rates may also mean a more
difficult spring transition.
Proper timing results in a gradual transition from the
warm-season turf to the cool-season turf and back again. Some
common indicators for timing include:
* Soil temperatures at a 4-inch depth approaching 75 degrees
Fahrenheit.
* Night temperatures consistently in the 50s.
* Average midday temperature below 70, or two to four weeks
before the average annual first killing frost.
Soil-to-seed contact essential
The best way to make the actual overseeding successful is to
get
good soil-to-seed contact. Seedbed preparation generally consists
of close mowing or scalping, with some light vertical mowing, and
sweeping or vacuuming up the loose plant debris.
Generally, the more the turf is opened, the better the
establishment rate, but the more competitive the cool-season turf
will be in the spring. Seeds that germinate in thatch or above
the soil are more likely to dry out and die.
After dragging the seed into the soil, irrigate three to five
times per day until the seedlings are well established. But the
total water applied during a day would seldom exceed 0.5
inches.
Irrigate without causing puddling on the soil surface, for
free
water encourages disease. After the seeds germinate, gradually
cut back on the frequency and increase the time of watering until
you can establish a normal irrigation program.
Begin mowing when the seedlings are 30 percent higher than you
want. Use a mower with sharp blades and mow when the grass is dry
to reduce seedling injury.
Fertilize three weeks after seeding
Wait to fertilize until after the seedlings emerge. That’s
usually three weeks after seeding. Earlier fertilizing may
encourage warm-season turf competition. Generally, 1 pound of N
per 1,000 sq. ft. per month is adequate.
Most turf managers are recognizing the value of a year-round
turf
management program to a smooth spring transition. Proper
fertilization, irrigation, mowing, thatch control, cultivation
and pest management all year affect the transition.
A good transition also requires knowing and making use of
normal
climatic conditions. Most warm-season turf grasses resume growth
when soil and night temperatures approach 60 degrees.
Change mowing heights
Maintaining a mowing height that prevents the overseeding from
shading out the warm-season grass is critical to a smooth
transition.
Lowering the mowing height as the soil warms will stress the
cool-season turf and aid in soil warming. When temperatures are
high enough, applying soluble nitrogen can encourage warm-season
growth and encourage cool-season decline.
The key to successful overseeding is the same as with most
other
turf management programs: proper year-round management and
understanding the growing conditions being dictated by the
weather.
