Successful moist-soil management is not just about flooding and draining water. The key is managing disturbance and water timing so beneficial native plants grow and produce seeds for waterfowl.
Design Matters: Include a Gradual Slope
Establish moist-soil units that can be flooded and drained using water control structures, with a gradual gradient that allows water depths ranging from about 1 inch to 18 inches when the units are fully flooded.
- This range of depths attracts a greater diversity of waterfowl because different species prefer different water depths.
- Shallow water (1–4 inches) attracts teal and shorebirds
- Moderate to deeper water (6–18 inches) is used by ducks such as mallards and gadwalls
A gradual slope also spreads birds out across the unit and allows food to become available over a longer period.
Flood Moist-Soil Units Slowly
Moist-soil units should be flooded slowly and in stages so food becomes available throughout migration and winter.
A common staggered flooding schedule is:
- 5–10% flooded: mid-August to mid-November
- 25% flooded: mid-November to late November
- 50–75% flooded: late November to late December
- 100% flooded: late December to mid-January
This staggered approach keeps fresh food available longer and prevents all food resources from being consumed early in the season.
Spring Drawdown Timing
Moist-soil units should be drained slowly beginning in March.
Water levels are typically reduced in 6-inch increments every 2 to 4 weeks. This gradual drawdown exposes mudflats over time and stimulates germination of beneficial plants.
General drawdown timing categories include:
- Early drawdown: March to May
- Mid drawdown: May to July
- Late drawdown: July to mid-August
Slower drawdowns often encourage greater plant diversity.
Let the Seed Bank Work
Most wetlands already contain a strong natural seed bank. When water is removed, desirable plants often emerge naturally.
Common beneficial moist-soil plants include:
- Native millet
- Annual smartweeds
- Nutsedges
- Panic grasses
These plants produce abundant seeds that are highly preferred by waterfowl.
Control Undesirable Plants
Moist-soil units should be monitored and managed for invasive or undesirable vegetation that can reduce habitat quality.
Common plants that may require control include:
- Lotus
- Cattails
- Alligatorweed
- Balloon vine
- Redvine
- Cocklebur
Control methods may include spot herbicide applications, mowing, or disking depending on the situation.
Herbicides are often used selectively when certain plants begin to dominate. Spot-spraying small patches is usually better than blanket applications so beneficial vegetation remains intact.
Examples of herbicides sometimes used include:
- Glyphosate for woody encroachment or heavy perennial vegetation
- 2,4-D for problematic broadleaf weeds such as cocklebur
- Imazapyr or imazethapyr products for certain invasive species or aggressive stands of undesirable vegetation
Disking for Plant Diversity
Disking can help reset plant communities and encourage desirable annual plants.
Disking moist-soil units during fall can promote plant diversity when the unit is drained the following spring. However, it may reduce food availability during the current fall and winter, so it should be used strategically.
Target disking in areas dominated by undesirable plants.
A good rule of thumb is to disk about 30% of the unit each year in a patchy mosaic pattern. Rotating disturbance like this helps maintain diverse plant communities and consistent waterfowl food production over time.
If you start seeing plants like smartweed, millet, sedges, and panic grasses, you are on the right track.
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