|
 Temperature and tolerance
Water temperature controls how long grasses can stay submerged and
survive, according to Dr. Bruce Branham, University of Illinois
professor and faculty Extension specialist. “Spring flooding with
cold water often results in minimal damage. Summer flooding with
warm water can cause rapid turf death if submerged more than a day
or two. Turf grasses vary significantly in their tolerance to
flooding. Fine fescues have poor submersion tolerance and can be
killed in as little as a day of submersion under warm water. On the
other hand, creeping bentgrass has excellent submersion tolerance
and can tolerate several days of flooding. Kentucky bluegrass has
medium submersion tolerance while perennial ryegrass has fair
tolerance to submersion injury.” (Beard, 1973)
Tips and timing
If the water came and went, but left the lawn covered with silt, the
silt should be removed as soon as possible with water from a hose.
This will allow the grass blades to start producing energy to aid in
recovery. The floodwater filled all the available pore spaces in the
soil displacing any soil oxygen. All plants need that soil oxygen to
actively absorb nutrition from the soil. In areas where water has
stood for many days, the grass plants are not likely to have
survived and more recovery or repair will be needed.
Table 1 Timetable
for seeding (can vary by 2 weeks or more)
|
Region |
Spring |
Fall |
|
Northern |
April |
Aug 15-Sep 7 |
|
Central |
Mar 15-Apr 15 |
Aug 15-Sep 15 |
|
Southern |
March |
September |
Adapted from Master Gardener
Manual University of Illinois
Seeding at the
proper time allows grass seed to germinate, grow, and be mowed
several times before the growing season ends. “Seeding can be done
any time of year, but the best chance of success occurs when seed is
planted in the late summer/early fall timings shown in Table 1,”
according to Branham.
Spreaders,
seeders, and species
Seeding options include a traditional broadcast seeding using a drop
or centrifugal spreader or using a rental “slit seeder” that cuts
through the dead grass and thatch layer and places the seed directly
in the soil at the proper depth. For areas up to 200 square feet,
you can get good seed-soil contact by buying a small amount of
topsoil and lightly covering the seed that was broadcast over the
area.
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This approach is practical for relatively small areas, but for
larger areas, a slit seeder will give you the best results. If using a slit
seeder, be sure to go in two directions to ensure a better stand of grass in the
coming weeks.
Grass seed is sold a couple of ways, and what you choose depends on your needs.
Blends combine several grasses of the same species (i.e. all cultivars of
Kentucky bluegrass) or as a mix combining different species (i.e. Kentucky
bluegrass and perennial ryegrasses). Your choice depends on the quality of lawn
you want to have or maintain and the sun-shade pattern. In older lawn settings,
a mixture may be preferred since over time a single species blend naturally
becomes a mixed lawn. Perennial ryegrasses can germinate in as little as 3 to 5
days while bluegrasses can take 10 to 14 days. If the lawn has been growing in
shade, consider fine fescues being much more shade tolerant than bluegrasses as
part of the mix.
If only a portion of the lawn has been damaged, you should identify what species
are present and match the seed you purchase to the species in the lawn. If the
lawn is mostly Kentucky bluegrass, then purchase a Kentucky bluegrass blend.
While bluegrass, ryegrasses, and fescues mix well and generally don’t appear
patchy. Branham also cautioned, “beware of very inexpensive seed, as it often
contains annual ryegrass. Annual ryegrass germinates very rapidly, usually in 3
to 4 days, but grows upright quickly, is a pale green in color, and will not
blend in with other grasses in the lawn.”
Weeds and their seeds
As the water recedes, many kinds of weeds can and will show up from the seeds
left behind from flooding. Some will germinate but not tolerate mowing and
naturally die as the lawn is mowed. However, there will be the opportunity for
lots of weed seed germination the following spring –over 90 percent of weeds are
spring germinators – and some of them will have the same fate and not tolerate
of being mowed. Annual weeds that germinate each spring are killed in the fall
by frost, but to prevent future populations, do not let them self-seed. If
perennial weeds establish themselves and survive being mowed, then weed control
treatments will be needed to remove them from the lawn. Whatever direction
taken, focus on establishing the lawn, weeds can be managed later. Satisfactory
recovery of the home lawn can take two years.
Beard, J. B. (1973). Turfgrass: Science and culture. Englewood Cliffs, NJ:
Prentice-Hall.
[Written by Richard Hentschel,
University of Illinois Extension, Horticulture Educator]
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