Part 4: How Mulch Work Do You Want To Do In Your Garden?

Author: Teresa Watkins
Published on: Jul 7, 2004

How do you know when you’re finished with your garden project? Well, the final touch is spreading the mulch under all of your ornamental shrubs, trees, and around perennials for an aesthetic finish that shouts “TAH-DAH”. But using mulch in your garden is so much more that just the icing on the cake, it’s a smart move to help the environment and lessen your yard chores.

Mulching in the landscape stops erosion of dirt and sand from going into the road and stormwater drains and helps decrease the competition for water and nutrients that weeds and grass will cause. It reduces the amount of weeds in your garden beds by reducing the sunlight necessary for seed germination. Mulch also lowers soil temperatures, which helps decrease your water bills by slowing evaporation, allowing the plants to need less water. Any way you look at it, mulching is an absolute must in any sensible and responsible gardener’s landscape.

Yet it amazes me how such a simple concept of using mulch in the garden can be blown out of proportion and be overdone to the point of being not only wasteful, but becoming an actual detriment to the homeowner. People think they are doing the right thing when using the “more is better” approach; they don’t understand that creating mulch “mountains” of six to 12 inches of mulch around their trees defeats the purpose of what they are trying to accomplish: water conservation.

Mulch should be applied to a depth of two to three inches around planting material throughout the landscape while keeping it away from the trunks of shrubs and trees. You want to be able to see the flaring out of the trunk at the base of the tree. If you can’t see the flare, your tree or shrub is planted too deep. Plants need to breathe; when planted too deep, they struggle without oxygen and usually never recover from retarded growth or die. Keeping the mulch up against the trunk or using too much mulch will also cause fungal diseases and rot. Especially with citrus trees — this is a good time to let you know what not to mulch! Do not mulch under the leaf drip of any citrus trees. Citrus needs good drainage and likes dry, sandy soils.

Another reason for only using two to three inches of mulch around your plants is that if you use more you will prevent any rainfall or irrigation to soak into the ground. The organic mulch will absorb the water and with high temperatures, evaporate before getting to the root system.

So what type of mulch should you use? Which one is the best — organic or non-organic?

The answers are whatever you want and both types can be best — it’s up to your personal preference, how much you want to work, and your purpose in using it. Organic mulch – such as pine bark or wood chips -- is preferable when you like to dig around and turn your soil, allowing the mulch to decompose into soil. Non-organic mulch – rocks, pebbles, or the newer rubber mulch, a recycled product from used tires – doesn’t need replacing and can be another source of color and texture.

The benefits of using organic mulch is that if you use certain wood mulches, they become a pervious groundcover that will allow percolation of water into the ground, allowing easier decomposition and eventually enriching your soil. You can also help the environment by using recycled organic mulch from your own yard waste or municipal recycling center, which is often free. Organic mulches can be a good source of compost while adding a natural, tropical, or wooded forest ambiance to your garden design. Types of organic mulches available are cypress, eucalyptus, pine bark, meleleucca, and shredded recycled wood products.

The downside of using organic mulch is that they require more work when you have to replace it (some wood types more often than others do) every one to two years. Organic mulches, such as cypress, meleleucca, and eucalyptus will fade quickly too, going from glossy golden browns and grays to matte, dull colors in a matter of weeks. Organic mulches like pine bark nuggets and pine needles can last for up to three to four years, keeping their color the entire time depending on your soil conditions and location. Speaking of color, there are mulches now on the market dyed to resemble redwoods and other unnatural color schemes. This is a choice that only you can make with your design palette. My advice is that if your mulch is the prettiest element in your landscape, you may need to rethink your landscape design. Colored mulches work best in designs of evergreen, non-flowering landscapes that also take into account your house colors. If in doubt, use a color wheel and keep your landscape palette, including your mulch within the same color group. Let your natural mulches be the aesthetic framework for your garden mural.

Non-organic mulches like rocks, stones, pebbles, and lava rocks can be a more permanent solution for the “Stepford”, non-maintenance yard. Rocks can be used to contribute to a southwestern theme for a desert garden or add unique interest to a water garden feature whose theme is carried throughout the yard. Advantages of using pebbles, stones, or rocks in your landscape as mulch is that it reduces maintenance — you won’t have to replace it except maybe once every ten years or so, if installed properly with a meshed landscape fabric underneath it. If you don’t use landscape fabric, you will see your stones quickly sucked into the chasms of the earth below, benefiting an unknowing but grateful gardener in China. Make sure you have cleared your garden bed of any weeds with tubers, rhizomes, or bulb-like roots. They will thrive underneath garden mesh even without sunlight and heat and you will find that you have even more weed problems in the future.

Using pebbles or stones underneath your plants though has more disadvantages than advantages, in my point of view. When you use stones, make sure that it is exactly what you want. If you change your mind after spreading a ton of pebbles underneath all your garden plants, who is going to pick them up to get rid of them when you change your mind six months later? My suggestion is that you use organic mulch first and then work your way to rocks if your garden is new. Established, full-grown plant gardens can be easier to define exactly where you want to use pebbles and you won’t be apt to change your mind after you have them down. Rocks and stones will also create hotter environments around plants, which will need more watering and may wilt easier in the summer heat.

Rubber mulch is the latest innovation in mulches on the gardening scene, again, with its pros and cons. The value of rubber mulch is that it’s a pervious surface, allowing water to drain into the earth, replenishing ground and surface water, and it’s not attractive to insects. Rubber mulch is also an excellent groundcover for parks, children’s playgrounds, parking lots, and personal car and boat common areas. It is a softer surface so if you are concerned about children hurting themselves, this is an excellent choice but make sure you buy the better quality rubber and not the cheap rubber mulch which still has protruding metal in it. With rubber mulch, you want quality. It’s also a permanent alternative, not needing replacement, so make sure it’s what you ultimately want. Rubber mulch has the distinct advantages of having hundreds of rainbow choices to select with blues, purples, greens, pinks, yellows, and oranges.

I have seen a homeowner’s landscape mulched with teal blue rubber around his tropical plants; it not only was colorful but also gave me a feeling of Caribbean ocean coolness that you would not get with wooded mulches. If you have a pool landscaped terrace, tropical colored mulch would add to the festive surrounding. The disadvantages of rubber mulch are few, but there are some. Mostly it’s the aestethics of using rubber — you may not want to use artificial mulch in your organic landscape. Costs are also higher than organic mulches but then you don’t have to pay to replace it every year either. The other point is that the color may affect the temperature of the rubber. Dark colors will absorb heat more readily than lighter shades. As with dyed organic mulches, be careful using colored mulches in your design as it may camouflage your flowers rather than highlight them.

Serious concerns regarding rubber mulch that have not been academically substantiated fully is that of petroleum leakage and the mulch's combustibility. There are environmental studies showing both pros and cons of rubber mulch and individually each homeowner should decide what is best for their landscape. If forest fires are a concern in your area and you want to use mulch, you may want to choose the permanent solution of rocks, not wood or rubber mulch around your house.

One myth of mulch that I would like to dispel is that “mulch attracts termites”. Scientifically, there’s good news and bad news regarding mulch used in the landscape. The good news is that mulch doesn’t attract termites, which is a myth, according to research studied by Dr. Duryea of the University of Florida/IFAS Entomology department (http://cfyn.ifas.ufl.edu/scape.html). The bad news is that in the Southeast, there are between one to three million termites per acre of property whether you mulch or not — that’s even if you use rocks. Dead snags, shrubs, trees, compost piles, with any decomposing wood is considered a food source for termites, so it’s not a question of if you are going to have termites, but when! The termites are not necessarily coming for the mulch as much as a food source, but rather for the warm moisture that the ground retains in the soil from having the mulch underneath planting material. So, if you are over-watering, keeping the ground wet around the foundation of your house, even if you use non-organic material, you will be more likely to attract termites closer to your house. You know that air conditioner hose drip outside your house that is constantly leaking all summer long? It’s an excellent source of moisture to attract termites. To keep your house foundation as dry as possible, follow these recommendations:

1) Follow irrigation schedules for best management practices. Over-watering can cause more insect problems.

2) If you are concerned about termites, use meleleucca mulch. Meleleucca was the only mulch in UF/IFAS research studies that termites would not eat. (Duryea, UF/IFAS, 2000)

3) Keep mulch and planting material from house foundation two to three feet away.

4) Use only two to three inches of mulch at a time. Closer to the house, use only one inch of mulch to allow foundation to dry out.

5) Repair or direct all water drips, i.e. gutters, leaky irrigation equipment, air conditioners, away from foundation.

Using mulch can relieve you of many garden chores, such as weekly weeding, watering often, and frustratingly replacing plants that die from stress of heat. Along with less work, mulching can add the finishing touches that will add an air of professionalism to your garden. Then you can stand back with arms outstretched saying “TAH-DAH!” and listen to your neighbors and friends’ ‘oohs and ahs’ of admiration.

They will know that you are a great gardener, but you will know that you’re a sensible and responsible gardener as well!

For more information and links on mulch and compost:

Mulch - http://cfyn.ifas.ufl.edu/scape.html

Composting - http://cfyn.ifas.ufl.edu/compost.html

Rubber Mulch - http://www.americanrubber.com