By: Pam Brown, ELW resident
With the copious amounts of rain that has fallen over the last couple of months, landscape mulch is quickly decaying into the soil. Fall is a good time to refresh landscape beds with a covering of new mulch.
Mulch prevents loss of water from soil by evaporation, suppress weeds, and moderates soil temperature. It can improve absorption of water into the soil and reduce erosion. I favor organic mulch because it will add organic matter to our infertile soil as it decomposes. In addition, mulch adds beauty to the landscape. You don’t have to remove old mulch when you apply new. Just add the new mulch on top of the old and the old will just continue to decay adding much needed organic matter to the soil.
Two to three inches of mulch is the proper amount to add to landscape beds. It is important to keep mulch a couple of inches away from the base of plants to keep fungal diseases from developing.
With trees, a ring of mulch is desirable to protect the trunk from string trimmers used to remove grass. Keep the mulch away from the base of the trunk of trees as well. Mulch piled up against the trunk encourages unwanted roots above the soil line that can girdle the tree as well as also encourage fungus.
Some environmentally friendly and sustainable organic mulch choices are:
- Pine bark – a waste by-product of the lumber and pulp paper industry
- Pine Straw – from plantations or your own pine tree – my personal favorite
- Eucalyptus – chips or shredded – farmed sustainably on plantations
Utility mulch or recycled yard waste – usually available free from Pinellas County Utilities – good for areas that you need mulched but do not what to spend lots of money. It is not the most attractive, however, you can put down 2 inches of this mulch then cover it with about an inch of more expensive mulch to help control cost.
Melaleuca – an invasive tree here in Florida that is being harvested and ground for mulch. It is said to resist some insects including termites. It is usually sold as Floramulch.
Enviro-mulch – is a 100% organic wood product. According to the manufacturer, this ecologically friendly environmental mulch looks very much like a cypress mulch, and is an alternative to cypress, eucalyptus and colored mulches. This mulch is ground from all natural, virgin wood primarily oak and Florida pine.
Mixed hardwood – colored mulch – This mulch could be ground pallets or other wood by-products. It is dyed many colors, but red seems to be the most available. There is concern that this mulch could contain CCA-treated wood that contains arsenic or other poisons. The EPA has stated that chipped or ground CCA-treated wood is a hazardous and it is not allowed in garden mulch.
Oak and other tree leaves – this is a great way to use these natural products. If you have large leaves, run over them with a lawn mower to mulch them so that they don’t blow in the wind. Once in place, they can be covered with a layer of one of the mulches mentioned above to improve the look.
Cypress mulch is probably the most abundant in the stores, but I discourage using it because large stands of native Cypress trees are being cut to produce it. It is not farmed sustainably and is not usually a by-product of lumber production. In addition, it tends to mat down and not allow water percolation through it into the soil as well as the other mulches.
Rock mulch is popular with some people and it does give a uniform appearance. Rocks are not organic, so they do not add any fertility to the soil. But, they are permanent and do not need to be refreshed as often. One type of rock mulch that can cause some problems is marble chips. Calcium carbonate can leach out of these rocks causing the pH of the underlying soil to be alkaline. Some landscape plants (azalea, holly, Ixora, Camellia) cannot absorb sufficient iron from alkaline soils and can become deficient. Use an acidifying fertilizer especially for these plants to keep them healthy.
Rubber mulch is good for paths I suppose. However, research at the University of Washington found that zinc leaches out of these mulches at levels that are toxic to plants. There is also concern about chemical leaching when using it in children’s play areas and even concern about the volatile gasses which could be toxic that are released when the rubber mulch gets hot. Rufus Chaney of the USDA Agricultural Research Service, after over 20 years of research concludes that on the zinc factor alone, ground or chipped tire material should never be used in gardens or landscaping. I have also read that tire rubber crumbs are being used as bulking agents in commercial compost products. This really concerns me. The Black Kow Compost web site states that they do not add any type of fillers to their compost, so I assume this one is safe to use.
The question always arises about mulch and termites. A research study was done at the University of Florida (http://edis.ifas.ufl.edu/fr075) using, Eucalyptus, Melaleuca, Pine bark, Pine straw and Utility mulch. Termites fed on all of the mulches, but Melaleuca was the most resistant. Utility mulch was the most consumed then Pine.
In Florida, termites are already in our soil. Mulch increases the ability of termites to survive where they are already established by keeping the soil moist and temperatures moderate. Mulch applied greater than 4 to 6 inches thick up to the foundation can provide a bridge over the treated perimeter of a structure, allowing termites to walk over from landscape to house and avoid contact with soil treated with termiticides. Ideally it is best to keep a 12 inch area adjacent to the foundation free of mulch or other ground covers. Mulch is useful in keeping mud from splashing up against a house so, if you feel you need to use it, the recommendation is that no more than a thin layer (about one inch) of mulch be placed within twelve inches of the foundation to allow the soil beneath to naturally dry if you need it. Drying out is the termite’s worst enemy. You will also want to avoid watering next to foundation walls.
Termites are everywhere in the Florida soil environment, so the best defense is to keep termite protection up to date with soil treatments and/or bait systems. You can access additional University of Florida/IFAS Extension information about termites at: http://edis.ifas.ufl.edu/topic_termites