May 30, 2001
Stillwater Gazette
Betsy Halden

Organic mulches for gardens and landscape plantings

Have you wondered if and why you should use a mulch around your new plantings? Have you questioned the advantages of using an organic mulch? Organic mulches serve several important functions . They help control weeds, conserve soil moisture, and stabilize soil temperatures. They reduce soil erosion by reducing the impact of raindrops and water runoff. They can help reduce the severity of some diseases, such as blights on tomatoes. They help keep fruits, vegetables, and flowers free of rain spattered soil. They also reduce fruit and vegetable spoilage. Organic mulches also provide an attractive background for landscape plantings.

The type of mulch determines how much should be applied. Most organic mulches should be 2 to 4 inches in depth. You can select the mulch according to factors such as availability, cost, appearance, function, and durability.

Here are the characteristics of several organic materials which may be used as mulches.

Lawn clippings. Allow lawn clippings to dry before applying to garden beds. The fresh, green material will settle and form a dense mat. Grass may produce an unpleasant odor. If the lawn has been treated with a broadleaf weed herbicide, don’t use the clippings until after the lawn has been mowed two or three times. The best source of grass clippings is a well-maintained lawn. Clippings from a weed-infested lawn will likely contain a large amount of undesirable weed seed, such as dandelion, plantain, and crabgrass. Grass clippings are not long-lasting and work best in vegetable gardens or annual flower beds.

Straw. Straw that is free from crop and weed seed is an excellent mulch for vegetable gardens and strawberry beds. Wheat, oat and soybean straw serve as good mulches. If you don’t have a readily available source of straw you can buy it a local nursery or garden center. Straw may provide a winter habitat for mice and other rodents. Be careful when using it around trees and shrubs.

Leaves. Leaves should be shredded or composted before applied as a mulch. Shredded or composted leaves do not mat down as readily as whole leaves, are less likely to blow away in the wind, and decompose more quickly. Shredded or composted leaves are an excellent mulch for vegetable gardens, raspberry plantings, perennial flower beds, and around trees and shrubs. Leaves make a poor winter mulch for strawberries and herbaceous perennials.

Pine needles. Pine needles are light, airy, they decompose slowly, and they make an attractive mulch. They may last several years and may be easily removed if necessary. Pine needles are acid in reaction and make an excellent mulch for acid-loving plants. They also can be safely used in vegetable gardens and around landscape plantings. A large, well-established windbreak is a good source of pine needles.

Cocoa-bean hulls. Cocoa-bean hulls are a by-product of chocolate production. Cocoa-bean hulls are light, easy to handle, and have an attractive brown color. They also have a delightful aroma. Unfortunately for chocolate lovers, the aroma lasts for only a few days. Although cocoa-bean hulls are relatively expensive, a mulch depth of 1 to 2 inches is sufficient. Cocoa-bean hulls are an excellent mulch for annuals, perennials, and roses. The material generally lasts only one growing season.

Shredded newspapers. Shredded newspapers or whole sheets may be used in a vegetable garden. Most newspapers use organic inks so we do not need to worry about lead contamination. If you use newspaper sheets, place a layer of 6 to 8 sheets between plant rows in the garden. Water the sheets so they stick to one another and to the soil surface. Then anchor them down with soil to prevent them from blowing away in the wind.

Wood chips. Wood chips make an excellent mulching material. They are available from local arborists and tree trimmers. The chips are obtained by passing tree and shrub trimmings through a mechanical chipper. Wood chips should be composted for at least one month to reduce the risk of transmitting disease to plants. Wood chips work best as a mulch around trees and shrubs and in perennial beds.

Bark mulches. Bark mulches are available shredded or as chips, nuggets, or chunks. They are often available in bulk quantities from nurseries and landscapers. Bark mulches are attractive, weed free, and they decompose slowly. Bark mulches are best used around trees and shrubs and in perennial beds.

There are several Extension publications on mulches. For additional information visit the Yard & Garden Line News at www.extension.umn.edu.

The Yard & Garden Line is a great resource for gardeners. If you have a question about garden or landscape plants, insects, wildlife, plant disease, soil testing call the Yard& Garden Line at 612.624.4771 in the metro area or 888. 624.4771 in greater Minnesota. All services are free of charge except for sending samples or talking to the University Yard & Garden Clinic experts.

Betsy Halden is a Master Gardener with the University of Minnesota Extension Service. University of Minnesota Extension Service materials were consulted in the preparation of this column. You can reach Betsy Halden at eahalden@comcast.net