Choosing and Installing Mulches
Mulch is used to cover the soil in a landscape or garden. It is often composed of tree bark, leaves, needles, wood, or grass. Sometimes mulch is made from stone and other inorganic materials, such as recycled tires.
Read on for answers to common mulching questions and a list of mulch types. We also offer help calculating how much mulch to purchase for your project.
Water savings, erosion control, weed suppression, and of course aesthetic appeal — there are so many reasons to add mulch to your landscape!
Why should I use mulch?
Proper mulching is an essential component of any Florida-Friendly landscape. Perhaps most importantly, it is the cornerstone of a great weed-control program. Mulch keeps the soil moist longer after irrigation, too. This gives plant roots extra time to soak up water. Mulch also protects plants' roots from extreme temperatures by creating a buffer between the soil and the air.
And mulch isn't just good for your plants; it's good for your soil. Organic mulches can add nutrients to the soil as they decompose. This improves your soil's aeration, structure, drainage, and ability to hold nutrients. Mulch can even help reduce erosion and protect plants from certain diseases.
Of course, choosing mulch is as much about appearances as it is about landscape health. In areas of deep shade, turfgrass and ornamental plants won't thrive. And some areas are too difficult to mow or irrigate to sustain healthy turf. Consider mulch as an attractive and Florida-Friendly alternative to bare ground in these shady and problematic areas.
Which mulch is right for my landscape?
When selecting a mulch, consider not only cost and color, but also origin, durability, and nutrient content.
Cypress is an example of a mulch with a questionable origin. Unfortunately, some of this mulch comes from Florida's endangered wetlands. Because its origin is difficult to determine, the Florida-Friendly Landscaping™ Program does not recommend the use of cypress mulch. Another mulch with an origin to reconsider is utility mulch. It comes from local trees and brush and can bring weed seeds and other pests along with it.
Durability is another important consideration. Organic (once-living) mulches decompose over time. As they do, they settle, reducing the depth of your mulch layer. At this point weeds will begin to germinate again. Erosion and evaporation from the soil will increase. When the depth falls below two inches, it's time to replenish the mulch. You can do this easily by adding another thin layer of mulch on top of the existing bed. Replacing the mulch entirely isn't recommended; you may damage surface-level plant roots.
Inorganic (never-living) mulches, like pebbles or rubber mulch, are very durable. They will last a long time and don't settle like organic mulches. That said, their nutrient content is zero so they will not improve the soil below them. And because these products do not decompose, they can become a nuisance out of place. You will need to keep an eye out for mulch straying into your lawn or other un-mulched areas.
Below are descriptions of the mulch options available at most home and garden stores:
Pine bark is a byproduct of the forest industry. It comes in ground and nugget forms and has a rich brown color. Pine bark settles slowly. One study by UF/IFAS found it to maintain two-thirds of its original depth after two years.
Pine straw (needles) comes from pine plantations, which produce paper and wood products. They give a very natural look to landscapes. And, unlike some mulches, pine straw is not likely to wash away because the needles knit together. Pine straw is among the least expensive mulches, but it breaks down and settles quickly. You will have to re-mulch the area often.
Fallen leaves (including grass clippings) can be raked up for free in your landscape and used as mulch. This type of mulch is high in nutrients but decomposes quickly. You'll need to rake regularly to keep your beds covered. Like pine straw, leaf mulch brings a very natural look to the landscape. Large leaves, like sycamore, may require mowing to prevent the mulch layer from matting.
Cypress mulch is composed of both wood and bark. Cypress trees grow in Florida's forested wetlands. They are often harvested for lumber and used in fencing, flooring, furniture, and other products. Leftover pieces are made into mulch, but cypress mulch may also come from whole trees cut from wetlands. As previously stated, the Florida-Friendly Landscaping™ Program does not recommend the use of cypress mulch.
Mixed hardwood mulch is produced from scrap lumber, recycled pallets, or tree stems too small for use in manufacturing. Aesthetically, it is an excellent substitute for cypress mulch. Hardwood mulches are often dyed to add red, brown, black, or gray color to your landscape. They settle faster than pine bark but significantly slower than pine straw or fallen leaves.
Melaleuca mulch is made from the exotic invasive trees. It gives the same traditional look as mixed hardwood and cypress mulches. The product is cured at a high temperature to kill any seeds so they won't germinate in your garden. It settles very slowly, meaning it will last a long time. In one study by UF/IFAS, melaleuca mulch outperformed pine bark and cypress mulch in durability.
Eucalyptus mulch typically comes from plantations in South and Central Florida. Trees there are grown specifically to be made into mulch. They grow quickly, so this mulch is considered renewable. Eucalyptus mulch is slightly less durable than cypress but longer-lasting than utility mulch or pine straw.
Utility mulch is sold or given away for free by many utility companies. This mulch comes from the material gathered when trimming trees and plants growing too close to power lines. Be aware that it can come with weed seeds and other undesirables. Sometimes dirt and leaf matter comes mixed in, too. For these reasons, utility mulch may not be a good choice for flower and vegetable gardens. It is, however, ideal for driveways, walkways, and natural areas.
Gravel and pebbles can be used as mulch. As inorganic materials, they won't contribute to the soil's nutrient content or water-holding capacity. Be sure to first install a woven ground cloth to keep stone mulches from sinking into sandy soils. Inorganic mulches last a long time, but need to be regularly cleared of debris to look their best.
Rubber mulches made from recycled tires are not recommended by UF/IFAS. They are generally less effective than organic mulches in suppressing weeds. This recycled material also absorbs heat, leading to extremely high temperatures in the ground beneath. Finally, some UF/IFAS Extension staff are concerned about the possibility of toxic chemicals leaching into the soil as the material slowly degrades.
How much mulch should I buy?
Florida-Friendly Landscaping™ recommends mulching to a depth of 3 inches. One cubic yard of mulch will cover 324 square feet of ground at 1 inch deep, or 108 square feet at 3 inches deep. At a three-inch depth, one cubic yard of mulch will cover an area about 10 feet wide and long.
To find out how much mulch you need to cover a larger space, you'll need to calculate the square footage of the area.
Rectangular areas: Multiply the length (L) of the planting bed by the width (W). Example: 5 feet long X 10 feet wide = 50 square feet to cover.
Circular areas: Measure the distance from the center of the circle to its edge. This is the radius of the circle. Multiply the radius by the radius again, then multiply the answer by 3.14. Example: 5 feet from the center to the edge X 5 feet from the center to the edge X 3.14 = 78.5 square feet to cover.
Irregular areas: Estimate these areas by dividing them into circles and rectangles. Add the smaller areas together to estimate the whole.
Once you have your square footage, multiply it by the desired depth of the mulch. Finally, divide that answer by 324 (the amount of mulch needed to cover one cubic yard). This answer will tell you how many cubic yards of mulch you need to cover your area. Example: (128.5 square feet to cover X 3 inches deep) divided by 324 = 1.2 cubic yards of mulch needed to cover.
How do I install mulch?
When applying mulch in the home landscape, follow these simple guidelines:
Maintain a 2- to 3-inch layer around established trees, shrubs, and bedding plants. Coarse materials, such as pine nuggets, may be applied 4 inches deep, but don't allow mulch to accumulate to a greater depth. Adding more mulch can harm plants if the mulch intercepts rain and irrigation meant for plants' root systems.
Rake older mulch to refresh its appearance and benefit plantings. Some mulches can become matted, preventing water and air from seeping through.
Avoid "volcano mulching." When mulch is piled against the base of a tree, it holds moisture. This encourages rot in the trunk. Mulch piled against the trunks of young trees may also create a habitat for rodents. These animals chew the tender bark, and can ultimately kill the trees.
Mulch to the drip line or beyond. The mulched area around the tree should be at least 8 feet in diameter. In the forest a tree's entire root system, which usually extends well beyond the drip line, would naturally be mulched by fallen leaves.
When using rock mulch, a little goes a long way. Rock mulch should be used minimally in the landscape. Reserve it for use on pathways, in dry creek beds, or under downspouts.
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More from UF/IFAS
- Improving Weed Control in Landscape Planting Beds
- Landscape Mulches: How Quickly Do They Settle?
- The Facts About Termites and Mulch