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Photo: N/A, License: N/A, Created: 2014:03:27 12:37:06

“My trees and shrubs need to be mulched again — already?”

As spring is kicking into high gear, have you heard yourself saying this?

Before you look at your graying mulch beds and decide to mulch again, perhaps you should rethink the whole issue. Let’s consider the function, appearance and types of mulch.

Functional value of mulch: From an arboricultural perspective, which is the practice and science of the cultivation, management and study of individual trees, shrubs, vines and other perennial woody plants; the functional value of mulch is its most important aspect. Properly installed mulch preserves soil moisture, reduces soil compaction, discourages competition, protects against temperature swings and protects against trunk damage. In northeast Pennsylvania, the best functional mulch available is sold in bulk as “natural brown mulch.” This is available by delivery or pick-up from any garden center. Natural brown mulch readily decomposes, has natural tannins [astringents] to prevent seed germination and, in time, “knits together” to reduce washouts. Because of the benefits of mulch, studies show that a tree properly mulched will grow faster than trees grown in a lawn or on bare soil.

Aesthetic function of mulch: For most homeowners, the aesthetic function is the most important aspect of mulch. Homeowners are interested in the color of their beds, which is why colored or dyed mulch is used. This type of mulch retains its color longer than “natural brown mulch.” However, dyed mulch has significant problems. First, it is made from “white wood,” which is often composed of shredded pallets, meaning it does not readily decompose. In fact, in order to decompose, “white wood” actually temporarily takes nitrogen away from plants. Studies have shown that trees grown in dyed mulch grow slower than trees not grown in dyed mulch. Dyed mulch also lacks the tannins found in natural mulch. Since it decomposes slowly, dyed mulch does not seem to “knit together” like natural mulch, making it susceptible to washouts. The most important problem with the aesthetic function of mulch is that since homeowners apply it for color, they often apply it too often. This not only costs money and time, but the buildup can be harmful to plants and buildings. As a general rule, mulch should not be closer than eight inches from wooden components of buildings and mulch should not touch the trunks of any plants.

Alternatives to mulch: There are several alternatives to mulch that you can use but each has its own set of issues. For example, gravel is a poor alternative to mulch; although it retains its color, it is difficult to maintain and may leach harmful compounds into the soil, such as excess alkalinity. Grass clippings are an excellent mulch; although they begin looking ridiculous, in a short time they weather to a reddish-brown, and provide excellent function. Compost retains its color and adds nutrients to the soil. However, it may lack the water retention and weed prevention character of other mulches. Groundcovers such as pachysandra provide an excellent alternative to mulch.

So, perhaps this year, you might want to think about maintaining instead of adding to your mulch.
