How Do Weeds Prevent Wind & Rain From Eroding Topsoil?

Tenacity

• Anyone who has pulled even a single weed encounters some of the systems that help weeds survive on all kinds of land. Typically, the strongest part of a weed is its root system. Weeds, such as purslane, chickweed and morning glory, typically have thin, fragile stems that break easily, but grow back quickly making it hard for the gardener to eradicate. Tough, wide-spreading root systems make weeds excellent soil-holders, as original plants send out runners or rhizomes to establish colonies of plants. Roots of weeds like field bindweed can rapidly grow 15 feet or more from the main plant.

Multiple Reproduction Systems

• Prolific seed production making spreading easy characterizes many weeds. Seeds further survive several means of transportation to new locations: blown by the wind, eaten and excreted by birds and animals, adhering to animal fur and human shoes or clothing. Purple loosestrife plants may generate as many as 30 flower stalks, producing more than a million tiny seeds per plant per season. New plants are produced by a variety of means besides seeds. Japanese knotweed spreads via seeds, rhizomes and plant fragments discarded but not destroyed by gardeners. While this can result in squeezing out of native species, these aggressive aliens form soil-holding thickets and clusters.

Size and Scope

• The Plant Conservation Alliance Alien Plant Working Group's "Least Wanted" list serves as a reminder that not all weeds are little. Russian olive reaches heights up to 30 feet, and black locust, tree of heaven and Siberian elm are all on the invasive list. Heavy drinkers with widespread roots, large weeds both help control water flow and serve as primitive windbreaks.

Mixed Benefits

• Some weeds, while not an ideal long-term solution to erosion problems, contribute to soil renewal, making eventual planning of more useful ground-holders possible. Several "Least Wanted" stars, including black locust, Russian olive and white clover, all share the ability of legumes to restore nitrogen to soil. White clover can be used as a cover crop, plowed under improving soil tilth until replaced with a native or productive crop. The U.S. Natural Resources Conservation Service also offers reminders that the line between weeds and valued native plants is thin. A chart of native prairie plant root systems shows plants like goldenrod and a number of grasses that some gardeners would treat as weeds, all with soil-hugging root systems ranging from 4 to 12 feet in depth.