FAQ About Mulch

Frequently Asked Questions

about Mulch

Q: I am re-landscaping my entire yard, and instead of mulch, rocks or pine needles, I am planning on using shells. Will shells create any type of problem for my trees, shrubs or flowers?
(Question from Naples, Florida)

A: Generally shells are much like a stone mulch. Except shells will slowly leach calcium into the soil as they very gradually degrade. If you already have a high pH (soil measure of acidity or alkalinity), which means your soil is alkaline, then using a shell mulch would slowly raise the pH. Also most Florida well water has a high (alkaline) pH which will also raise the pH of the soil over time. And generally most plants in our landscape prefer or do better with soils that are just slightly acidic. So you should have your soil pH tested at your local Cooperative Extension office. It is usually a county department listing. Also, shells, like stones, used for mulch will be warmer than an organic mulch layer. And plants generally do better when soil temperatures are moderate not hot.

Having said that I still would encourage you to use organic material for the mulch for the following reasons:

Our Florida soils are sandy with little organic matter and organic matter is beneficial for plant growth by aiding water retention and slowly breaking down to provide nutrients to the plants. Organic matter also provides higher levels of micro-organisms and humus that are beneficial to soils and plants. Once you decide to stop adding organic mulch to your soil, the existing organic matter in the soil decomposes within several months and is gone. And there is no additional organic matter other than an occasional decaying root that will replenish this valuable soil asset — organic matter.

Organic mulch is by far the best thing and one of the least expensive things you can do for the long-term health of your landscape. And the organic mulch should be placed directly onto the soil with no weed mat which would inhibit the breakdown and movement of the organic mulch into the soil.

For more on organic mulching check out my web site page: Mulch.

As you can see I do have a organic mulch bias. But I have developed this bias over the years watching poor sandy soils become poorer and plants doing poorly.

Good luck however you decide to proceed.

Q: What kind of mulch would you recommend to use in beds around and close to our home. In the beginning we used cypress mulch and discontinued it a number of years ago because of the rampant destruction of cypress trees. Then we went to pine bark and encountered an ant problem, i.e. they entered the house. Our pest control people told us that eventually  these ants would attract termites. So we removed all of the pine bark and are left with the above question. Short of investing in stone (pebbles) I would greatly appreciate your advice. Thank you. (Question from St. Augustine, Florida)

A: There are many reasons stones should not be used as mulch. A couple reasons are increased heat retention and lack of improvement of organic matter of the soil the stones cover. In fact, since there is a weed mat barrier between the stones and the soil, any organic matter that existed in the soil becomes used up (decomposes) and disappears leaving a very low quality soil for plants and trees.

As I understand it, the main reason people want to switch to stone mulch from organic mulch is the belief that stones will not attract subterranean termites while organic mulch is said to be a virtual picnic for termites. The University of Florida entomology department did a study around 2001 or so on termites and mulch around buildings on the Gainesville campus. The research found that it is the moisture retention of mulch rather than the “food value” that makes an area hospitable to termites. In other words stone mulch is just as attractive as organic mulch to termites because it keeps the soil moist.  The recommendation is to keep mulch (stone or organic) about 12 inches back from building foundations.

The statement by your pest control service that ants (or conditions that are hospitable for ants) would eventually attract termites sounds like something made up on the spot by someone who is unknowledgeable or someone wanting to sell additional services.  The conditions for ants vary by the ant species and there are many species of ants in our environment just outside our front door. And these ant conditions really don’t have much in common with subterranean termite conditions. The pest control guys should put up a chemical barrier for the ants (just as a different type of chemical barrier is put up for termites) and stop making things up that will unnecessarily scare people.

Now the best type of organic mulch has a lot to do with your personal preference. We know that cypress mulch should not be used for ecological and sustainability reasons. From the research I have done, the best mulch available is the free chipped tree material that tree services produce every day. This material is a mixture of chipped logs, bark and green leaves and twigs. It good, readily available and it is free.

I have found another mulch that is composted and screened. It is available at several locations in north Florida but the closest is the Flagler C.D.S. (Construction Demolition Service) northwest of Bunnell. Another is the Mulch More company at 11436A Philips Hwy. in south Jacksonville. You can drive a pickup trunk or small trailer there and get a yard of mulch for about $7 or $8. The composted mulch is really good quality and I recommend it for all trees but especially for veteran trees. It is composted and is steaming when dumped into your pickup truck. Great stuff. For more information on mulch you can go to my web site:   Mulching To see some of the composted mulch under the Maltby Oak in Palatka, go to: Maltby Mulch You can see the mulch spread under the entire canopy of the Maltby Oak in the third photograph.

Keep in mind that mulch creates an environment that is conducive for all kinds of microorganisms and some larger critters. That is part of our Florida environment.  It is this diverse community of microorganisms and critters that help break down the organic mulch releasing humus and nutrients into the soil for the plants and trees. Organic mulch creates an environment that is so beneficial to trees. We are making the soil like the forest floor. And another benefit is mulched plant beds rarely require fertilizer.