Thursday, August 18, 2011

To mulch or not to mulch?

Mulch in the landscape does more than just affect the aesthetic quality.
  • Mulch conserves soil moisture - reducing how much water needs to be put on the landscape.
  • Mulch aids in the suppression of weeds - meaning less time hand pulling weeds and/or less herbicides sprayed on the landscape.
  • As the mulch breaks down it improves soil nutrient content and soil structure. If you have a home like many others in Miami with "fill" soil this is a huge benefit.
  • As organic mulches break down they tend lower the soil pH (this is helpful in Miami because we have high pH soil).
  • Mulch can create a grass free zone around landscape plants reducing damage to tree trunks during lawn maintenance.
Types of Mulch
Spread organic mulches around the base of the plants about 3-4" thick, but do not place mulch right up against trunk of plant.

  1. Pine Bark - This is a sustainable mulch product. The nuggets break down slowly and a re superior at weed prevention. The shredded bark is not as effective in preventing weed growth, but is less likely to float away.

  2. Other forest-based mulching products - Include eucalyptus (fast growing tree sustainable resource) and melaluca (good use of an invasive tree). A study from University of Florida found that melaluca mulch requires replacement less often than other mulches.
  3. Cypress bark - Although this mulch is attractive it is not a renewable resource and for this reason other alternatives are being promoted.
  4. Wood chips - less expensive than bark but can cause a depletion of available nitrogen once they break down. This includes the dyed mulches. The color mulches are dyed using an iron-oxide stain which is non-toxic, some of the wood however comes from scrap wood and may have been pressure treated wood which may increase the risk of arsenic leaching from the product as it breaks down. The color mulches should not be used food crops. Wood chips should not be used immediately adjacent to the wall of a dwelling in order to decrease the chance that these materials will attract termites
  5. Recycle your own yard waste to create mulched areas (see pic below). Some plants will self-mulch such as bamboo-meaning they drop leaves which act as mulch. Consider using leaf debris to build up your mulch. If you want that mulched look, use 2" of leaf debris and top it off with 1" of mulch.

A variety of materials are available: marble chips, river rock, pea gravel and lava rock. These materials will not breakdown and they will have no effect on soil fertility (nutrients) or structure. Some of these materials may retain too much heat and should only be used in shaded or low-light areas. If you are using an inorganic mulch consider using a geotextile mat ("weed" mat) to prevent the rocks from mixing with underlying soil.

This post was taken from the publication titled "Mulching Practices for South Florida" written by Dr. John Mclaughlin and Charles Yurgalevitch. To read the entire article Click Here.


  1. Thanks for this great informations!!


  2. Another informative blog… Thank you for sharing it… Best of luck for further endeavor too.