Get It Growing for 10/11/24
If you use mulch in your landscape, chances are it has thinned out over the summer and is in need of refreshing. If you’ve been putting off this chore, consider this: Mulching isn’t just about aesthetics. It’s actually an important gardening task that can do wonders to protect plants and trees as we approach our cooler season. And if you’ve never mulched before, it’s never too late to take advantage of the many benefits of this practice.
Whether you use pine straw, bark or some other material, most types of mulch are natural — so they decompose over time and must be replenished regularly to be most effective and look their best. We recommend reupping on mulch every fall and spring so plants and trees can enjoy a nice, thick (but not too thick!) layer year-round.
Here’s our comprehensive guide to using mulch.
Benefits of mulching
Mulch suppresses weed growth, reducing competition for water and nutrients — and the amount of time we have to spend pulling up those unwanted plants. Mulch also reduces evaporation, promotes better water filtration, retains moisture and wards off soil erosion. Perhaps most importantly, as the mulch breaks down, it adds organic matter to the soil, boosting its nutrient content and porosity.
In short, mulch is one of the best — and most affordable — steps you can take to improve the health and longevity of your plants and trees.
With fall and winter weather on the horizon, mulch offers another key benefit: insulating plant and tree roots from the cold. In warmer weather, mulch puts a barrier between the soil and the oppressive elements, helping keep roots cooler.
Mulch, of course, has aesthetic benefits too. Nothing dresses up a flower bed or vegetable garden like some fresh mulch. In shady areas beneath trees, most turfgrasses struggle to grow, so mulch is a good way to cover up the bare ground. At the same time, it creates a physical buffer that protects the roots, bark and trunk of trees from mowers and string trimmers.
Types of mulch
As the U.S. Department of Agriculture defines it, “Mulch is simply a protective layer of a material that is spread on top of the soil.” Several materials fit that bill, so you can pick the one that best suits your needs.
Composted pine bark. Hallie Dozier, an associate professor of forestry at the LSU AgCenter, says this is one of her favorite mulches. It’s readily available at any garden center. You can buy 2-cubic-foot bags for use in small areas or have a load delivered for larger projects. Because of its coarse texture, pine bark won’t break down too quickly — but the lightweight pieces don’t stay in place as well as other types of mulch.
Bark mulch is great underneath trees and in landscape beds. Avoid it, however, in vegetable gardens, where it can tie up nitrogen from the soil and prevent the nutrient from reaching plants.
Shredded or chipped wood. Mixed wood chips offer a wide range of options. Some shredded mulches are dyed red, brown and black; others are all natural. Most that are available commercially are partially composted and ready to contribute organic material and nutrients to your soil.
You may also be able to get fresh hardwood chips from your local utility or a local arborist — giving you a longer-lasting product and keeping these chips out of the landfill. As with bark mulches, fresh chips are best under trees and not in vegetable or flower beds.
Pine straw. Easy to find, this is an ideal mulch for vegetable gardens that also works well in ornamental beds. It does a good job of staying in place. Because its texture has lots of spaces between individual needles, pine straw is a champ at trapping warmth in the winter. But this airy texture also means it isn’t as good at blocking weed growth as wood mulches.
If you have pine trees on your property, you’re in luck. Simply sweep up the needles, and voila — free mulch.
Fallen leaves. In Louisiana, leaves fall from now until early spring, with live oaks providing the final round. This makes for Dozier’s absolute favorite mulch. Not only are leaves economical; they’re earth-friendly too. Many insects, including native bees, butterflies, moths and fireflies overwinter in fallen leaves and dead stalks in the garden. And using your own leaf litter keeps it from going to the landfill.
Still, leaves decompose quickly — and some gardeners won’t find them to be as attractive as commercially available mulches. You can make leaves look nicer by chopping them with a mulching blower or mower, which also will help them stay where you put them.
Other choices. Paper and cardboard, mixed compost from your yard, landscape fabric, plastic mulch, shredded rubber, rocks — the list goes on when it comes to materials that can be used as mulch. While nonorganic materials such as plastics, rocks and rubber will suppress weeds and moderate temperature, they do not give the benefit of improving the soil and may not be as breathable as an organic mulch of bark, chips or leaves.
You can use old boxes — ideally, use ones that aren’t coated with plastic film — held in place by rocks to mulch an area. Cover with a thin layer of another type of mulch to pretty it up if you like. Cardboard is excellent at suppressing weeds and breaks down quickly to improve the soil.
Mulching method
You can use your hands to spread mulch in small spaces; in bigger areas, you’ll probably want to use a rake. Your layer of mulch needs to be 2 to 4 inches thick to be most effective. Anything thinner will permit weed growth and won’t allow for moisture retention and temperature moderation. Lay it on too thick, and you’ll smother roots. Deep mulch traps too much moisture and heat, impedes proper airflow and encourages fungal and bacterial infections, among other problems.
Special care should be taken when mulching around trees. Spread out mulch horizontally to the estimated edge of the rootzone. If that’s not possible due to space or drainage considerations, at least extend the mulch to the drip line of the tree canopy — or just as far as you can practically go. Dozier says there is no such thing as a mulch ring that is too wide, at least from the tree’s perspective.
Don’t pile mulch up into volcano-like shape around the base of the tree trunk. Keep the transition space between the roots and trunk, referred to as the root collar, free of mulch so the tree can breathe. Piling mulch high against the base of the tree can cause its bark to deteriorate, allowing fungi and pathogens to enter the tree.
You may want to consider installing some kind of edging or barrier to contain mulch if you haven’t already. This will keep mulch where it should be — plus it helps visually set off mulched areas from the rest of the landscape.
Jason Stagg and Hallie Dozier demonstrate proper mulching techniques.
Use a rake to spread bark mulch into a 2-to-4-inch layer. Photo by Randy LaBauve/LSU AgCenter
Take care to keep mulch from touching the base of the tree trunk. Photo by Randy LaBauve/LSU AgCenter
The tree’s root collar should be kept free of mulch. Photo by Randy LaBauve/LSU AgCenter
Leaf litter is an economical, earth-friendly mulch option. LSU AgCenter file photo
Pine straw is a popular mulch that works well in beds, such as this one in front of the LSU AgCenter Hammond Research Station office building. LSU AgCenter file photo
Piling mulch into a volcano-like shape that touches the base of the trunk can lead to tree health problems. LSU AgCenter experts discourage this practice. LSU AgCenter file photo