Photograph by Joe Mac Hudspeth, Jr. ·


Wonder Weeds for Waterfowl

From the Spring 2007 issue


Webster’s dictionary defines ‘weed’ as, “Any undesired, uncultivated plant.” However, an ecologist recently said a weed was, “A plant without a home.” The latter definition seems fitting for a community of wild grasses and sedges that many waterfowl managers and hunters call ‘moist-soil’ plants.

As the name implies, moist-soil plants are adapted for living and reproducing in wetlands. They thrive in seasonally flooded wetlands, which are not flooded year round but usually remain wet during the growing season.

Moist-soil plants generally are annuals that produce lots of seed or tubers each year because of their short life span and need to spread their genes at the end of a single growing season. Abundant production of seeds and tubers is good news for waterfowl as ducks and geese worldwide feed on these natural morsels of energy and other important nutrients.

In the Lower Mississippi Valley (LMV), where wetlands and agriculture abound, migrating and wintering waterfowl feed heavily on both natural and agricultural seeds. However, wildlife scientists from Mississippi State University (MSU) recently reported in Delta Wildlife (summer 2005) that the abundance of waste rice—grain missed by combines during harvest—and other crop seeds has decreased significantly over the past 25 years.

The decrease is largely due to earlier harvests which leave seeds in the field to decompose, get eaten by blackbirds, snow geese, and rodents, and sprout but not produce a mature plant and seed head in fall before wintering waterfowl arrive.

The MSU scientists also reported that moist-soil seeds and tubers can fill part of the ‘grain gap’ due to the decreased abundance of waste crop seeds. Their published research revealed that harvested rice fields in the LMV in late fall contained only about 70 pounds of waste rice per acre compared to almost 500 pounds of moist-soil seeds per acre in managed wetlands in the same region.

Not only do moist-soil seeds partially compensate for the decreased abundance of waste crop seeds, but many of the seeds and tubers targeted in moist-soil management provide nearly as much food energy to waterfowl as agricultural seeds. For example, MSU scientists have reported that mallard ducks can obtain, on average, about 3.2 kilocalories of energy by eating a gram of corn, rice, or soybean compared to about 2.8 kilocalories from a gram of moist-soil seeds such as from barnyard, foxtail, and panic grasses. Interestingly, tubers of chufa sedge, also common in LMV wetlands, may provide even more energy for waterfowl than corn, based on feeding trials with Canada geese.

Indeed, moist-soil plants seem to be ‘wonder weeds’. So how do we grow them?
A good summary of moist-soil plant management practices is covered in the “Waterfowl Habitat Management Handbook” by the MSU Extension Service (Publication 1864). Briefly, to produce moist-soil plant communities, managers should disk soil in spring or early summer and then try to keep soils moist during the growing season. Disking soil every year or two and keeping it moist during the growing season promotes germination of the natural ‘seed bank’ and stimulates vigorous plant growth. However, disking should not be done in the heat of summer (e.g., August). Soil disturbance during the ‘dog days’ of summer generally promotes germination by undesirable plants such as coffeeweed, cocklebur, and sicklepod.

If undesired weeds appear, herbicide applications may be needed to prevent them from overtaking the moist-soil plants. Again, the handbook mentioned above identifies a variety of herbicides useful in controlling unwanted weeds. Always remember to use herbicides that kill broad-leaf weeds and vines (e.g., 2, 4-D) but which do not harm desired moist-soil grasses and sedges.

What about growing moist-soil plants with ‘hot’ foods such as rice, corn, and milo? Actually, rice, corn, and milo are agronomic grasses that compete quite well with moist-soil grasses and provide greater food energy for waterfowl than most natural seeds. MSU scientists are studying what they term ‘dirty rice’ and ‘grassy corn and milo.’ Basically, moist-soil grasses and sedges are allowed to grow amongst the grain crops which are not harvested but left for wintering ducks.

Grassy corn in particular can increase potential duck use per acre about ten-fold or more because corn generally yields more bushels of seed and has a greater energy value than moist-soil seeds. To produce grassy corn, habitat managers plant corn rows about three feet apart and apply herbicide once before or soon after planting to enable the corn to grow about a foot tall and establish a good root system without weed competition. The wide spaced rows allow sunlight to reach grasses and sedges that will grow amid the corn plants. Fertilizer and irrigation also may be necessary for production of normal cobs.

After grassy corn fields are flooded in fall-winter, they provide corn and abundant moist-soil seeds and aquatic invertebrates—the latter of which are critical sources of protein for ducks. The flooded grass under the corn is critical habitat for invertebrates. Indeed, the combination of high-energy corn, the stalks providing cover for waterfowl, and the protein-rich invertebrates—all within ‘swimming space’ for waterfowl—make flooded grassy corn a ‘duck magnet’ especially for mallards.

As said earlier, another definition for weeds is “A plant without a home.” From our perspective, moist-soil plants are ‘wonder weeds’. Try adopting these ‘wonder weeds’ into your ‘family’ of duck holes. If you do, you’ll provide a ‘home’ for weeds and waterfowl this winter.