Planting an Oak Tree in soil with Coral Rock

NanMatt · 29th July 2008, 01:32 PM

We dug a hole to plant our 12 foot oak tree and found huge coral rocks. We broke as much rock as we could but there is still a lot left. We took the chance and planted our tree. Even though there was a lot of soil , I am having second thoughts.
Will the tree root and thrive or will the coral rock prevent it from happening?
I live in Southern Florida and our soils are filled with coral rock.

Garry Brockley · 29th July 2008, 05:54 PM

How deep was the hole before you hit coral? did you add any other growing media, how big was the root ball

Eric Frei · 29th July 2008, 06:59 PM

Florida Plant Care --The Soil: Creating Lush Landscape Begins with a Healthy Soil

Quote:

Fertilizer management of South Florida's alkaline soil can help any gardener or landscaper improve plant care and create a lush tropical environment.

Blame thousands of years under the ocean for South Florida's challenging growing conditions in the soil for gardeners and landscapers today.

That's because marine deposits accumulated over that period. The ocean left a mixing of coral rock with sand and shell rock – all of which makes for an unusual planting media and difficult plant care.

“The problem with this soil is that virtually all of the beneficial aerobic bacteria – which are needed to breakdown fertilizers into a form that is available to many plants – are non-existent,” says Florida horticulturist Alexis J. Smith.

The calcium carbonate from the coral rock makes the soil alkaline; by definition, a pH always above 7.0. Soil rich in calcium carbonate is called calcareous.

Smith explains that the pH is so high that most of the nutrients become locked up in a form that is unavailable to plants. The high sands do not have any plant nutritional-holding capacity, and the fertilizers wash down through the soil past the plant roots.
Common Deficiency

The most obvious nutritional deficiency due to high pH is iron deficiency, which is most common in ixora and gardenias. A pH of 8.5 is 1000 times more alkaline than what ixoras require for lush dark green growth.

Smith points out that the usual chlorotic (yellowing) condition in ixora is because of lime-induced iron deficiency. However, iron is not the only element that is bound up. Magnesium, potassium, zinc and manganese are also unavailable.

While the ixora -- like other acid-loving plants such as hibiscus, gardenia, citrus, and Allamanda -- can be an attractive landscape plant, there are a few requirements gardeners need to know to keep ixora healthy and flowering in your yard.

“All acid-loving plants will require more fertilization management than plants that are adapted to growing in alkaline soils,” says Gail Keeler, Institute of Food and Agricultural Sciences, University of Florida. (November 2003)

“Mostly this involves being aware of the pH (or acidity) of the soil you are planting in. A pH of around 5 is good for ixora; this pH is slightly lower than for most landscape plants.”
How to Create Healthy Soil

According to Smith, there are a number of other ways to deal with theses soil conditions and create an environment for healthy plantings.

1) Start with a soil analysis on the entire project. Understanding the conditions that exist will guide the nutritional management of your plants.

2) Make a selection of plants that are tolerant of existing soil conditions. Cocoplum, for example, is tolerant to high pH, whereas ixora is intolerant and will turn chloritic within a few months in a calcareous soil.

3) Use fertilizers that have chelated materials. Keep in mind there are different chelates made especially for the higher pHs.

4) Use acidifying fertilizers. When combined with organic material, they reintroduce the microorganisms and bacteria needed for the reduction and breakdown of fertilizers.

5) Finally, to prepare healthy plants for winter in South Florida, make sure to cut plants back early and fertilize in late summer or winter.

Keeler and her UF team also recommend that you avoid planting Ixora or any acid-loving plant close to your concrete foundation, and screen soil in planting areas for any concrete fragments that may cause soil pH to be too high for good plant growth.

A few tips.

Always observe other vegetation and how it's going/growing.

Always observe what is indigenous to the area.

Many of our large eucs grow on shale and rock. The smaller and finer roots explore every fissure and hole in that rock. The larger roots often on top under a layer of mulch ... yes they do blow over.

One advantage is the rock is porous.

Roots aren't rock breakers, sure they can exert some pressure but in reality they'll find an easier way. Also they want water and nutrient.

Mounding up soil and mulch will help.

NanMatt · 30th July 2008, 01:07 AM

Thanks for your replies. We dug the hole about 2 1/2 feet and 1 x the size of the root ball. We put in some potting soil and mulched it. We couldn't make the hole wider because of the rocks surrounding it so we decided to dig deeper.
I've see other oaks thrive but perhaps with proper fertilization considering the tough growing conditions in South Florida.

29th July 2008, 01:32 PM	#1
NanMatt I'm new here so be nice Join Date: Jul 2008 Location: MIAMI, FLORIDA Posts: 3	Planting an Oak Tree in soil with Coral Rock We dug a hole to plant our 12 foot oak tree and found huge coral rocks. We broke as much rock as we could but there is still a lot left. We took the chance and planted our tree. Even though there was a lot of soil , I am having second thoughts. Will the tree root and thrive or will the coral rock prevent it from happening? I live in Southern Florida and our soils are filled with coral rock.

29th July 2008, 05:54 PM	#2
Garry Brockley Bayside Tree Care Brisbane Join Date: Jun 2008 Location: Brisbane Aus Posts: 1,641	Re: Planting an Oak Tree in soil with Coral Rock How deep was the hole before you hit coral? did you add any other growing media, how big was the root ball __________________ My business:- Brisbane Bayside Tree Care

30th July 2008, 01:07 AM	#4
NanMatt I'm new here so be nice Join Date: Jul 2008 Location: MIAMI, FLORIDA Posts: 3	Re: Planting an Oak Tree in soil with Coral Rock Thanks for your replies. We dug the hole about 2 1/2 feet and 1 x the size of the root ball. We put in some potting soil and mulched it. We couldn't make the hole wider because of the rocks surrounding it so we decided to dig deeper. I've see other oaks thrive but perhaps with proper fertilization considering the tough growing conditions in South Florida.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode