Mulch is any material placed over the soil to retard weed growth, maintain moisture, and improve soil conditions. Mulches also add a polished and well-maintained look to plantings. Generally speaking there are two main types of mulch: organic, and inorganic.
Inorganic mulches consist of gravel or small stones, and recently, recycled rubber. Because these mulches do nothing to improve the soil structure, they are generally only used in specific applications, such as paths, hardscaping, or other places where plants will not be desirable. Organic mulches, therefore, are preferred.
For mulching under trees in particular, you will want a lot of mulch, but not, perhaps, for the reasons you think. Mulch will improve the quality of soil, and the number of nutrients taken up by the roots. For this reason, you will want a layer of mulch over as much area as is practical.
Mulching as far as the dripline (the outer edges of where the rain sheds off the leaves) is a good rule of thumb, but tree roots generally reach much farther, and are only a few inches under the surface so the more you mulch (and reduce competition from grass) the more your tree will like it.
When it comes to mulch, more is not better. 2-4 inches of mulch under a tree is adequate. If you go too thick, you will starve the soil for oxygen, which is bad for the earthworms and other beneficial organisms, not to mention the tree itself. The so-called “mulch volcanoes” are not very good, either. The can harbor fungus or rodents which can damage the trees.
Mulches break down at different rates, but ordinary bark mulch does not need to be refreshed very often. If you are merely mulching to refresh the color, ask a landscaping company about vegetable-based dyes that can be spread over the mulch to improve the color without smothering your trees.
If you have any questions about mulch or mulching, contact us today.