16 Mar1998

Overstory #3 - Weeds as a Resource

Written by Kim Wilkinson and Craig Elevitch.

Weeds: A Problem or A Resource?

There is nothing either good or bad, but thinking makes it so. - W. Shakespeare

A very useful design principle is: Turn constraints or problems into opportunities. Weeds are often seen as major problems, and much energy and resources are spent fighting them. But are weeds really the problem, or is our perception of them the problem? What follows is a short exploration of some ways that weeds can be a resource for farmers, foresters, and gardeners.

Beneficial functions and uses of weeds

Weeds are vigorous improvers of land, constantly striving to create more diversity, organic matter, and abundance. Weeds on the land may be accomplishing what Nature knows needs doing there, better and faster than we are. For example:

Weeds support diverse soil microlife

Soil microlife feeds off plants. The diversity of plants on the surface is directly related to the diversity of microflora in the soil. Weeds can contribute greatly to that diversity. Removal of weeds to bare the soil reduces diversity. It is very likely that there is important soil life or function being supported by some family of weed that has yet to be documented. For example, several nitrogen fixing species used to be considered weeds, but are now valued and actively cultivated by many farmers.

Weeds control erosion and conserve water

Bare ground loses moisture to the air on sunny days, and soil to erosion when it rains. A healthy groundcover of living plants will conserve moisture and prevent erosion, and weeds can be part of that groundcover.

Weeds support insect and bird life, reduce risk insect pest problems

Butterflies, spiders, bees, dragonflies, praying mantis, ladybugs, and other insects need food and habitat to thrive. A variety of insects will also support birds. A healthy mix of insects encourages balance between predators and prey and reduces the chance of insect "problems."

Weeds are a source of food and medicine for people

Many plants that are sometimes considered weeds are prized as nutrient-rich vegetables or medicinals all over the tropics. A few examples in Hawai'i (all escaped introduced species) include amaranth, portulaca, bitter melon, chayote, Spanish needle and gotu kola. Many of these tolerate drought or other harsh conditions far better than cultivated vegetables, and can be quite delicious.

Weeds are a source of food for animals

Animals can be integrated in the farm to do most of the weed resource management. For example, ducks are used for selective weed control, because they can often be trained as ducklings to develop a taste for some weeds, and will eat those plants first when allowed to range freely.

Weeds provide food for other plants

In the tropics, nutrients essential to crop plant health are primarily in the organic matter, not bound up in the soil. Organic matter needs to cycle through the soil for nutrients to get to plants. Cutting weeds back and mulching plantings with them is a common practice with tropical farmers, and increases crop plant health. It is important to cut the weeds before they seed to keep the seeds from sprouting right next to the crop.

For more about ways to work with weeds, including permaculture ways of handling very aggressive and competitive plants, please see the unabridged version of this article at our website, Working with Weeds.

About the Authors

Kim M. Wilkinson is the Education Director for Permanent Agriculture Resources and editor of The Overstory. She has B.A. degrees in Anthropology and Ecology from Emory University.

Craig R. Elevitch is an agroforestry specialist with more than ten years of public and private sector experience in tropical agroforest and forest management. He has a M.S. degree in Electrical Engineering (Dynamical Systems) from Cornell University.