The Biscayne Times

Apr 03rd
Soil Compaction Kills Your Trees PDF Print E-mail
Written by Jeff Shimonski, BT Contributor   
December 2019

Commercial “nutrient” injections won’t fix the issue

TPix_YourGarden_12-19hrough the loss of so much tree habitat, and the preference for open landscaping on residential and commercial properties, Miamians are being increasingly affected in obvious ways.

These days we all worry about driving down flooded roads after heavy downpours. People driving compact cars have a real problem on inundated roads, and even SUVs can stall in deeper water. More rainwater is running onto roadways because we’re covering all that land with impermeable concrete and compacting any remaining soil.

The photo that accompanies this article is of a local road I drive along several days a week. It was still raining when I took this photo. It had been one of those weeks when it seems to rain almost every day, and any open ground was probably saturated when I took the photo.

But I notice as I drive through residential areas -- and as you can see in this photo -- it’s rare for the entire street to flood. Plus, I’m seeing more flooding on roads next to newly constructed homes. As is clear in this photo, flooding occurs next to regular parking areas, even on bare ground, because the soil is so compacted that the rainwater just runs off into the street.

This area where the photo was taken has few, if any, storm drains. Thus it takes a while for the flooding to dissipate. In areas where there are storm drains, the water is just diverted to the ocean and bays near us.

Just think of the other stuff that flows into the storm drains along with the water -- lawn chemicals, fertilizers, and all the organic matter that landscapers blow off the properties into the streets, not to mention the dog crap that people leave on any open piece of exposed grass without picking it up. This is called “nonpoint source” pollution.

But I digress. The point here is that compacted soil left behind after new construction leads to many problems.

I came across one problem recently, after writing an after-the-fact tree evaluation on a newly built residential property where a number of live oak trees had most of their roots removed during construction.

I’d completed my report and sent it out to my client with a number of recommendations, including how to resolve the issues of compacted soil around the remaining large trees.

Tree protection fencing hadn’t been put up to protect the roots of these trees, as required during construction, and now the trees were suffering from soil compaction. That compaction keeps water and oxygen from reaching the tree roots, which then start to die. When the roots die, the tree’s canopy begins to thin out. Less water and fewer nutrients reach the foliage, so tree growth slows considerably.

A couple of weeks later, I got a call from a pest control company that also offers horticultural chemicals to clients. They had some questions regarding several large live oak trees on the right-of-way adjacent to the property that were in decline from soil compaction.

My client, who’d built the house, needed to make the trees look better before turning over the property to the new owner, and had contacted this pest control company to inject the trees with “nutrients” to make them look better.

The person from the pest control company asked me what kind of permitting was needed to inject trees in the right-of-way in that municipality. I asked why the company didn’t know the answer already, if they provided that kind of service. There was no answer.

I then asked if they’d read my report, which recommended “air spading” to de-compact the soil around the trees in order to let water and nutrients reach the roots. Again, no answer.

Frustrated, I then asked if they were aware that the injection service they were providing was only treating the symptoms, not the underlying causes of the tree decline, which would continue, despite their treatments. No answer, and the phone call ended.

I see the results of soil compaction everywhere in South Florida. During construction, municipalities rarely enforce the required tree protection zones, and as a result, trees that are left are in decline once construction is finished.

Then, because municipal code requires a few trees and some shrubs to be planted around the project, new landscaping is dug right into the compacted fill. But because the roots of these plants can’t grow into the compacted soil, and because any of the soil biota that could work with tree roots is dead, the new landscaping is almost entirely dependent upon regular fertilizer applications. Without regular fertilizer application, most of these trees decline -- and without substantial roots, they topple over in storms.


Jeff Shimonski is an ISA-certified arborist municipal specialist, retired director of horticulture at Parrot Jungle and Jungle Island, and principal of Tropical Designs of Florida. Contact him at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .


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