Flooded lawn management
Record rainfall and flooding can take a toll on turfgrasses too. The excess water limits the oxygen levels in the soil and literally drowns the grass. The first sign of trouble is raw sewage-like odor which indicates a lack of oxygen in the soil.
Bermudagrass and bahiagrass are most tolerant of flooding and centipedegrass is least tolerant. Zoysiagrass and St. Augustinegrass are intermediate. The extent of damage depends on the length of flooding and whether scalding occurs. Scalding occurs when two to four inches of water cover the grass in full sun, raising water temperatures high enough to damage the grass.
To assess turf damage, look for green leaves or green or white runners above and below the soil surface, or white roots. Green and white indicate a healthy plant while soft, milky white or brown stems and roots suggest the plant is dead. Lightly raking brown turf areas will help determine if some grass has survived.
Steps to consider in salvaging your lawn include the following:
- Improving surface and subsurface drainage. Keeping drains clean, digging temporary surface drains on putting in subsurface drains may be the first step.
- Removing any sediment like soil and organic debris on the surface by raking or shoveling will help surviving turf recover.
- Mowing off dead leaves is also helpful.
- Applying about one-half pound of nitrogen per 1,000 sq.ft. Should help encourage turf recovery and then follow normal maintenance practices for the rest of the year. If 40 to 50 percent of the area has healthy grass, you probably have enough present to "grow in" the rest.
If over 60 percent of your lawn is lost, consider the following options:
- Sodding which produces an instant lawn with less long-term mess.
- Seeding with centipedegrass, St. Augustinegrass or common bermudagrass. Bermuagrass established fast but is limited by shade. Seeding done late in the year is subject to winterkill, particularly when done less than eight weeks before the normal first killing frost date which is in late October in most of South Georgia.
- Vegetatively plugging can be done later in the growing season than seeding.
- Establishing a temporary cover with ryegrass or tall fescue. This should be seeded about the first of October. Perhaps Kentucky 31 tall fescue seeded at five pounds per 1,000 sq. ft. may survive if seeded in September or late August. Higher seedling rates will lead to disease and other stress problems and should be avoided. If tall fescue is used and centipede is wanted, the tall fescue will survive until next summer when centipede could be seeded or plugged into the tall fescue providing a gradual transition.
Finally, in conditions like these, keeping things simple and being patient are probably well warranted. Additional information can be obtained from you local county extension office.