Gardening in Larimer County

by Trudi Manuel
 Colorado State University Cooperative Extension Master Gardener
 Larimer County

Some of us remember the all-too-catchy jingle used by a major corn chip producer, “Munch, munch, munch a bunch of Frito corn chips.” Gardeners in Colorado who want to do right by their plants and vegetables should change the ditty to, “Mulch, mulch, mulch a bunch of organic matter right now.”

Gardeners know that watering and weeds are two of our biggest worries. Mulching helps reduce the amount of water needed to grow healthy plants, as well as control weeds and save our backs. Getting rid of weeds is a mighty task requiring diligence, persistence and plenty of mulching. According to research, mulching reduces evaporation from the soil surface and cuts water use by 25 to 50 percent. It helps to control weeds that rob moisture from the soil and compete with struggling plants.

In our arid climate, xeriscape landscapes continue to gain ground with gardeners who want to use low water-use plants and reduce water needs. The use of mulch placed around the plant, but not against it, is recommended. Mulch touching the stems of plants may encourage rodents or insects living in the mulch to feed on the plant and damage or kill it. Also, don’t be concerned if bark mulch has mold or a slimy substance underneath the top layer—this is the natural process of microbes breaking down the mulch into organic matter, thereby improving the soil.

Organic mulches, like grass clippings, pine needles, shredded bark, bark chips or chunk bark, straw, wood chips and leaves all have their advantages and disadvantages. Wood chips are long lasting and readily available, but texture and color uniformity can be a drawback. Chips also have to be reapplied when the bare ground shows or new plants are added to the garden.

It is recommended to apply mulch to a depth of three to four inches, with the exception of dried leaves and straw—these should be applied in a four to six inch depth. For a 100 square foot area, apply three inches of mulch; for an 80 square foot area, apply four inches.

Inorganic mulches include weed-barrier fabrics, rock and gravel. Weed-barrier fabrics reduce weeds, and if covered with mulch, are generally long lasting and a good substitute for black plastic.

As organic mulches decompose and the mulch is used to breakdown organisms in soil, some soil nitrogen deficiency occurs. Yellowing, primarily of lower leaves, is a sign of nitrogen deficiency. This can be corrected by adding two pounds of a complete fertilizer, such as 10-6-4, or one-quarter pound of ammonium sulfate to a 100 square foot mulched area.

For more information on mulch, see Colorado State University Extension Fact Sheet #7.214, “Mulches for Home Grounds”