An excellent tool for weed management and moisture retention in the garden, mulch comes in many price points and varieties. But which one is right for your yard?
The answer to that is complicated — and a little contentious among seasoned gardeners.
“If you ask three different people their opinions about mulch, it wouldn’t surprise me if you got three different answers,” said Kate Garland, horticultural specialist at the University of Maine Cooperative Extension.
The best mulch for the job will also depend on the crop — if a mulch is appropriate at all, that is.
“A lot of the fast season crops like radishes and lettuce, it’s not really practical to mulch them,” said Tom Roberts, owner of Snakeroot Farm. “Lettuce is really susceptible to slugs, [and] if you have a lot of mulch around it, you’re likely to have a lot of slugs around it. The same thing is true for any of your really fast growing things: basil, dill, cilantro — even broccoli, we don’t bother mulching because it’s so quick.”
For other crops, though, mulching is important to prevent weeds, improve moisture retention and reduce the amount of labor you need to put into your garden.
Roberts said gardeners should consider the goal of using mulches. If you are using mulch to suppress weeds, Roberts said consider which weeds you are trying to suppress. Annual weeds growing from seed might be easier to eliminate with mulches, while perennial weeds with fleshy roots such as dandelions or quackgrass may need additional measures.
“Are you trying to keep weeds down, are you trying to add moisture, are you trying to keep the soil cool?” he said. “There are a whole bunch of reasons you can choose one mulch over the other.”
Black plastic mulch
Laying down a sheet of black plastic with openings for where your crops are planted is a popular, inexpensive method for mulching. One of the primary advantages of black plastic as mulch — especially in Maine for warm-loving crops like tomatoes, peppers and cucurbits — is that black plastic warms the soil by conducting the sun’s heat when applied securely on a firm, level plot.
Black plastic is effective for retaining moisture, but weeding and watering must be maintained around these openings. Some sort of irrigation under the black plastic might be prudent, especially during dry years.
However, black plastic is wasteful, as the sheets are generally thrown away at the end of the growing season.
Landscape fabric lasts longer than black plastic and can be reused year after year. This is especially useful for landscaping, ornamental gardens and perennial crops. Landscape fabric is often topped with a layer of bark mulch or another organic substrate.
However, weeds can grow through the landscape fabric and become difficult to remove. Garland limits the use of this mulching technique in-between rows of the vegetable garden where she can easily sweep off dirt carrying weed seeds.
However, there are distinct downsides to landscape fabric, Garland said. After the fabric is laid down, it is often topped with a layer of bark mulch or another organic substrate. Over the years, she said, soil — along with weeds — can accumulate on top of the mulch and fabric as well.
There are a wide array of organic options for mulches, including shredded leaves, pine needles and straw. These mulches come with the added benefit that as they decompose, they can add helpful nutrients like nitrogen and carbon to the soil.
Roberts gathers organic materials like leaf litter and grass clippings from his neighbors over the course of the year.
“It’s amazing when you think about what you could use for mulch, you can look around and see all sources of mulch during the year,” he said.
Smaller plots likely do not require sourcing mulch from around the neighbor. To save costs for your personal garden, Garland said to look around your yard for whatever is available, whether it is leaves, pine needles or glass clippings.
Still, making mulch from yard waste may keep costs low, but it still requires advanced planning. There are lower-maintenance, less time-intensive organic options as well. Bark mulches and wood chips, for example, are readily available at many garden centers, and are good to use in a landscape around well-established plants. Bark mulch can be expensive and may need to be raked off between seasons for annual crops.
For perennial plots, adding compost to bark mulches can also prevent it from accumulating, helping soil retain its moisture, prevent weeds and adding nutrients to the soil. Straw or leaf litter or other lower-maintenance alternatives to bark mulch that can be incorporated into the soil at the end of the season, but you should be cognizant of weeds seeds that could be carried in these mulches.
Newspaper, cardboard and paper
A layer of any of these materials placed under a layer of straw or bark mulch will serve as an extra barrier to weeds while easing the potential aesthetic eyesore of damp, shredded paper materials in the garden.
However, there are a few things to consider before you use these upcycled mulches. For example, you may want to research the types of inks and glues that are used on the materials you are upcycling beforehand to make sure you aren’t adding anything toxic to the garden.
Though there are some variations in the cost of mulches, the contributions that mulches can make to your soil as well as their impact on the environment, a lot of choosing mulch comes down to your personal preferences.
“It varies so much depending on personal preference, but also what types of crops you’re growing, how much time you have and also your aesthetics,” Garland said.