Mulches for the garden

Conventional plastic rolls for covering the ground in and around plants and crops, of various colors, thicknesses, and manufacturers, have been used as ground covers since the 1960s.

Plastic forms resistant barriers that help reduce weed competition, conserves water, minimizes soil and water erosion, helps heat the soil to increase yield and crop quality and is used to get crops and plants to mature earlier.

Plastic does not transmit water, may create an adverse microclimate or very hot conditions especially in summer heat (when dark colors are used), and should be disposed of offsite since it does not break down and it has questionable environmental effects.

Determining how and when plastic ground covers are removed and where they are disposed of after the growing season may affect labor costs and disposal methods. Since plastic covers have limited recycling options, it is often taken to landfills, buried or burned which can release harmful chemicals into the environment and air.

If left out in the field it breaks into pieces, blows, or falls apart, but does not disappear. There are no good environmentally friendly alternatives to dispose of plastic. Where residual plastic is left in or outside the field there are known negative impacts to wildlife and water quality.

There are other alternatives to plastic. Fabric mulch or other woven (geotextile) fabrics and naturally occurring mulches have application for gardeners and farmers alike. Though fabric mulches do not break down in the soil and should be removed at the end of the season, they do transmit air and water and can serve as excellent weed, insulation and moisture control barriers.

They can be cleaned and reused for multiple years which can cut down on disposal costs. Many growers and gardeners regularly use crop residues including straw, hay, grass clippings, or leaves as mulches or cover and green manure crops which can be tilled into the soil. These types of mulches biodegrade well and can add valuable nutrients to the soil, assuming they have not been treated with pesticides, which are harmful to plants and animals. Sometimes these sources provide habitat for rodents or provide weed seed sources, so all materials should be used with caution.

Mulches continued next week.

For answers to gardening questions, contact the Master Gardeners at the WSU Grant-Adams Extension office at 754-2011, ext. 4313 or email your gardening questions to ga.mgvolunteers@wsu.edu. Visit our web page at grant-adams.wsu.edu.