Spring is just around the corner and you’re probably already thinking about how you’re going to hate dealing with all of those weeds. Hand weeding is great exercise, but it gets pretty tiring after a couple of hours, and herbicides are always a last resort.
In any garden or landscape the first line of defense against weeds should be mulch, and for good reason. Used properly, mulches not only stop weeds, but also help build the quality of the soil. There are so many possible choices that choosing the right one for you can be difficult.
The best mulches out there are what professional landscapers call organic mulches. These mulches are made of various types of bark, shredded or chopped wood, pine needles, leaves, or some other form of cut up plant pieces.
The great thing about organic mulches is that they not only stop weeds, they also enrich the soil as they decompose. Of course that does mean that they need to be replaced over time, but that’s a small price to pay for weed control and healthy soil. The organic mulches that break down the most slowly include pine bark and pine needles.
Leaves tend to disintegrate rapidly and blow away, however, they do have the not insignificant advantage of costing absolutely nothing. Because of how rapidly they disintegrate, as well as the possibility that they may have been treated with herbicides, grass clippings tend to be a poor choice for mulch.
A distant second on the list of mulches for your garden is gravel or rock. Gravel certainly stops weeds, but it doesn’t decompose or help the soil. Over time soil will work its way into your gravel and weed seed will fall onto these small, fertile areas. When this happens weed control is out the window. Raking gravel once a month or so is a good practice to keep weed seeds under control.
A final problem with gravel is that, periodically, people will use limestone gravel. This type of gravel really isn’t appropriate in the garden or landscape because it will change the acidity of the soil to the detriment of most plants. It is a mulch to avoid.
Perhaps the worst choice for weed control is rubber mulch. It offers nothing to the soil it covers, blocks rain water from getting into the soil, may leach toxic chemicals into the earth, and is difficult to rake.
For any mulch a depth of about two to four inches is best. Organic mulches will usually need to be reapplied once a year, though heavy applications of pine bark may last for two years and shallow applications of leaves may last less than a year. If you are mulching around trees and shrubs be sure to leave an inch or two of space between the trunk and the mulch. Roots can grow up into mulch and if the mulch is right against the tree roots may surround the trunk, eventually strangling the plant.
No landscape is ever weed free, but with proper mulching with an organic mulch early in the season you can get a head start on controlling weeds and building a strong soil.
Jeff Gillman is director of the UNCC Botanical Gardens.