The Benefits of Organic Mulch for Trees in the South Florida Urban Environment

Urban trees such as those present within south Florida are often stressed by their environment. Limited root space, poor soil, and lack of nutrients are common issues. While soil/foliar testing, root zone excavation, and fertility programs are encouraged, there are simpler ways to improve overall tree health. One of the most cost-efficient and effective ways to achieve this is mulching.

Mulch is simply defined as a substance which covers soil. Mulch comes in organic (wood chips, pine straw, leaves) and inorganic forms (rubber, landscape fabric, rocks). While both forms of mulch may help to retain soil moisture, reduce weed competition, and reduce soil temperatures, organic forms of mulch have greater benefits.

The most overlooked benefit of organic mulch in the urban landscape is its ability to improve the soil it is applied to. When mulch is applied to a typical sandy South Florida soil, for example, its immediate benefits are reducing erosion, dust, and water runoff. The long-term benefits are surprisingly far-reaching. When mulch breaks down, it adds organic matter to the soil. Over time, this simple amendment can increase soil fertility, water-holding capacity, reduce bulk density, and increase beneficial microbes. Basically, this helps improve the overall quality of the soil and provides a natural buffer to sudden changes that would otherwise impact tree health.

When assessing overall tree health, soil is of upmost importance. When the soil is healthy, overall tree health is greater, and the ability of the tree to ward off pests and diseases may increase. Mulch is an accessible, affordable, and relatively easy way to contribute to long-term soil health.

In the landscape, weeds and turf grass often compete with a tree’s critical root zone for water, nutrients, space, and light. Sod also has different fertility and water requirements than most canopy trees and palms.  For these reasons, it is recommended that tree owners remove sod underneath the dripline of the tree prior to mulch application. Removing sod will also reduce excess fertilizer and water use. Organic mulch may then be applied to a depth of 2-3 inches. Take care not to bury the tree trunk or major buttress roots (this often leads to rot) and keeping the mulch at least 6-12” away from the trunk is also recommended. Depending on the specific type of mulch used and site conditions, older mulch may be raked and replaced seasonally to increase aeration. These simple adjustments can reduce maintenance and costs for the tree owner and contribute to the overall health of our urban forest. 

For additional information about the tree benefits of mulch and organic matter please click here SL273/MG454: Soils and Fertilizers for Master Gardeners: Soil Organic Matter and Organic Amendments (ufl.edu).  (Guest Post by Kirstie McCullough, ISA Certified Arborist) 

                                                How to Properly Apply Mulch

 

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