When it comes to stopping weeds, mulch really matters
By Dawn Pettinelli - UConn Home & Garden Education Center
Home & Garden - posted Mon., May. 7, 2012
While planning, preparing, planting and maintaining gardens are some of my most savored activities, weeding is not usually a chore I relish. By far, the best way to cut down on weeding is the judicious use of mulch.
Mulch has many other beneficial effects aside from weed control. It insulates the soil from summer and winter temperature extremes, retains moisture, allows for increased penetration of rainfall, decreases erosion, reduces disease incidence and looks attractive.
Mulches are divided into two categories. Organic mulches are derived from natural materials which will eventually decompose, enriching the soil. Inorganic mulches include black plastic and landscape fabrics. New biodegradable mulches are being developed from cornstarch and cellulose.
Inorganic mulches are primarily effective during the growing season. Black plastic suppresses weed growth by excluding light. It can also increase yields of heat-loving plants like melons and peppers.
While quite practical in the vegetable garden, black plastic does have its drawbacks when used in more permanent plantings. If used around trees and shrubs, the plastic inhibits air and water exchange. This can lead to root die back, especially on poorly-drained sites. A better choice for such areas would be landscape fabric, which allows for water and air penetration. Persistent weeds like quackgrass can eventually grow through the landscape fabric, but it keeps most weeds at bay. Usually, landscape fabrics hold up for several seasons. They can be topped with organic mulches such as bark nuggets for a more pleasing appearance.
In my opinion, organic mulches are generally the best choice in the home landscape, especially for permanent plantings. For perennial and annual beds, small particle size mulches like shredded hemlock bark, buckwheat hulls, cocoa hulls or shredded leaves work well. For shrubs and larger ornamentals, use larger particle size mulches, such as bark or wood chips. The larger particle size mulches generally last three or four years before they need replacing.
Common mulch problems are artillery fungus, slime mold and sour mulch. Not putting on mulch too deep and fluffing it up occasionally generally keeps annoying fungal organisms in check. An inch of mulch around perennials and annuals and 2 to 3 inches around trees and shrubs is sufficient, but never pile mulch up around the crowns or stems of your plants.