MULCH MULCH MULCH
[The Kampong is an 11-acre (32,000 m2) tropical garden in Coconut Grove, an area of the city of Miami, Florida, USA. It is one of the five gardens of the non-profit National Tropical Botanical Garden (NTBG), and is open to visitors. An admission fee is charged.
The Kampong was originally the winter home of the famous horticulturalist, Dr. David Fairchild, in 1916. In his life, Fairchild introduced around 30,000 different plant species and variations into the U.S. At The Kampong, Fairchild created a garden that contained many of the plants that he obtained throughout his trips. Larry Schokman curated and managed the garden for many years until his retirement in 2008. - Editor, 2011]
The last six weeks have been hot and dry in Miami, while most of the country has experienced a series of snowstorms, rain, and cold weather. (This article was written in early spring. Ed.)
One of the secrets of growing healthy plants in these hot, dry conditions, in our rocky (oolitic) soils, is mulch, mulch, mulch. The benefits of organic mulch can only be described as superlatives.
When we started heavy mulching at The Kampong over ten years ago, we were warned by the skeptics and doomsayers that phytophthora would take its toll on the trees, fungus would be a problem, etc., etc. Many of these pessimists are now true believers.
Among the many benefits of mulch in our calcareous soil (if indeed it can be called 'soil') are its moisture retention, reduced evaporation from the dirt surface, pH reduced (i.e., mulch helps make our alkaline soils a little acidic), which in turn enhances the absorption of micronutrients by the plant. Heavy mulching also helps reduce weeds that continuously steal water and nutrients from the plants, and helps improve the tilth of the soil. Fewer weeds means lower maintenance costs. Weeds occasionally sprout in the mulch, but they can be pulled more easily from mulch than from limestone.
The mulch that is available to us usually comes from trees that are grown in our nutritionally deficient 'soils'. It is therefore important to remember that our plants still require extra micronutrients, preferably as a foliar application. (There are exceptions to this rule!) If there is a negative aspect to 'fresh' mulch, it is the carbon-to-nitrogen ratio which varies from 100:1 to 150:1. This means that more nitrogen is required to break down this 'raw' organic matter.
If extra nitrogen is not added, this process will 'steal' nitrogen from the very plants you are trying to help. To solve this potential problem, throw a couple of handfuls of urea, or any balanced granular garden fertilizer that you may have, onto the mulch which has been spread around your plants/trees.
How high can you pile mulch around your tree? At The Kampong we started out at 4-inches-high and slowly increased it to a height of 18 to 24 inches with only positive effects. We now have healthy earthworms crawling around previously barren/rocky areas. It is preferable not to pile mulch right up against the trunk of the tree, particularly citrus. Keep mulch 12 to 18 inches away from the base of your tree.
Organic mulch includes all biodegradable material, from wood chips to dry leaves, straw, grass clippings (should be mixed with a biodegradable material of a different size and texture; otherwise water cannot percolate through that matted mass of compacted grass, which in turn would generate too much heat and adversely affect a young plant). Newspapers and leftover salads and vegetables also form good compost.
If you are concerned that leftover vegetables might attract rodents, use a rat-trap or bait. The positive effects of using this type of organic material outweigh the negative possibilities of attracting rodents.
Gene Joyner, Chief Extension Agent of Palm Beach County, spreads a truckload of mulch around his plants five times a week. The plants at his "Unbelievable Acres" are unbelievably healthy!
Editor's note: [1994]
The many fully-grown trees at Gene Joyner's place provide a welcome canopy of shade for three or four understories of plants. The mulch under his trees is now several feet deep with not a blade of grass or weed to be seen. All of his plants flourish under their mulch cover.
The windbreaks on his 2½-acre garden are primarily Australian pines that tower 80 feet in the air, providing excellent protection from winter winds and several recent hurricanes.
Another bonus from the long-term application of mulch is that it attracts bacteria, insects and lizards which in turn attract birds and other creatures that are losing their habitat in our rapidly-urbanizing environment.
Fertilizer will not percolate into the aquifer, because it will be absorbed and utilized by this organic mass. We have also observed that fruit that fall from trees germinate very easily in the mulch. Maybe sometime in the future we might be able to grow some of the edible Chinese mushrooms in this matrix.
Using all your dead leaves and branches in your garden will not only improve your soil, but will also prevent the highest mountain in South Florida (Mount Trashmore!) from getting any higher, at increasing taxpayer expense.
So, the three secrets to healthy plants are MULCH, MULCH, MULCH!
This article appeared in the April issue of the bulletin of the Tropical Flowering Tree Society in April 1994. Mount Trashmore, a landfill, is the highest point of land in South Florida.
DATE: January 1995
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