University of Florida/IFAS Extension Director for Nassau County, Rebecca Jordi, provides expertise and tips about northeast Florida gardening and landscaping.

Looking Up At Tree Canopy, Old Oak Tree In Fernandina Beach
Looking Up At Tree Canopy, Old Oak Tree In Fernandina Beach

Gardening Q & A

QUESTION:  How far away can I plant from a tree?  LL

JORDI:  The general rule is to take the diameter of the tree at breast height and multiply it by 3.  You said the old tree was about 6 feet wide.  Yes, ideally this would be 18 feet out. This is obviously an old oak tree. The other thing to realize is the older a tree is, the less it likes things around it to change. Very similar to humans, the older we are the less we like to have things change around us. If you disturb the root area close to the tree you will likely see damage to the canopy or the top of the tree.

Size Of Mulch Area Depends On Tree's Diameter
Size Of Mulch Area Depends On A Tree’s Diameter

Prevent Future Tree Problems

I understand you want to plant within 2.5 feet of the tree, but this would not be wisdom. By doing this, you could turn the tree into a risk tree by causing the root area to become compromised and unstable. Here is an opportunity to prevent a potential problem in the future.  Consider mulching the area (2-3 inches deep with pine straw) under the canopy and placing a cluster of 3 container pots with shade loving plants. You would get the color you want while demonstrating the importance of protecting the root area of an old tree. The whole area under the canopy does not need to be completely covered with plants.  I would love to see trees in the landscape protected. 

Remove Grass From Under Canopy

One other easy step – remove the grass from under the canopy.  Grass does not grow well anyway as most require 8 hours of full sun.  Grass will not get enough sun under a tree. Trees and grass are terrible partners. Adding sod and soil on the roots of trees, especially older established trees, is a poor practice. Let’s protect our trees by following the appropriate landscape practices.

Now, before you go and get your chainsaw and start removing lower limbs from the trees to allow more sun on the grass, this is another common poor practice.  It makes the trees too top heavy which is another dangerous practice. Here again, humans are the cause of this practice and it can set the tree up for failure by toppling over because the weight is not distributed throughout the canopy. 

QUESTION:   What is the ideal soil pH for zoysia grass?  Mine has measured at 7.2.  CM

JORDI:   You soil pH is a little high for zoysia grass to be comfortable. Most plants growing here in Northeast Florida prefer the soil pH to be slightly acidic – between 6.0 – 6.5 and this includes zoysia, bahia, Bermuda and St. Augustine.  There are exceptions — there are always exceptions.

Zoysia Grass
Zoysia Grass

Centipedegrass requires an acidic soil pH of 5.0 – 5.5.  Bermuda and St. Augustine grow well between 6.0 – 6.5 but willtolerate a soil pH slightly higher than 6.5.  However, it is important to note this is an additional stress factor if the soil pH is not ideal. Remember pH is measured between 0 to 14; pH values less than 7 are considered acidic and above 7 are alkaline and 7 is neutral. When values are too low, some of the nutrients, such as potassium (K), calcium (Ca), or magnesium (Mg) located in the soil will not be available for the plant to absorbed through roots.  These plants can also show toxicity for other nutrients such as aluminum (Al), iron (Fe), or zinc (Zn).  In alkaline soils, iron (Fe), manganese (Mn), zinc (Zn), and boron (B) are often deficient. Soil pH can also affect beneficial soil bacterial and fungal activity, enhancing or inhibiting the development of soil-borne plant diseases or how efficiently microbes’ function as decomposing organisms.

Get Soil pH Tested!

It is critical to have your soil tested before selecting a lawn grass for our area. Builders, landscaper designers and HOA making the decisions for landscape plant selection really should consider pH before making their final decisions. Involving the local horticulture agents from UF/IFAS Extension is a good place to start.

Don’t Add Lime Without Soil Test

Something else to consider – we should not add lime to our landscape unless a soil test has been completed.  I know adding lime to soils in other parts of the country is a common practice – but it should not be here. Adding lime to the soil makes it more alkaline and the plants and grasses here prefer it slightly acidic.  Adjusting the soil to be more alkaline (raising the pH) is easy – changing the soil to be more acidic (lowering the pH) is NOT.  For more complete information read the UF/IFAS publication.

Bird's Nest Fungi
Bird’s Nest Fungi

QUESTION:  What can I do about the mushrooms popping up in my flower beds?  KB

JORDI:  There really is no chemical to kill them.  Your best management practice would be to pick them up immediately, bag them and throw them into the trash.  As soon as they show through the ground, remove them. This will eliminate spores from spreading and creating future mushrooms. They do not have true roots, so they pull out of the ground very easily.

Don’t Eat Wild Mushrooms From Landscape

Many mushrooms are saprophytes which means they feed on decaying material. In your flower beds, most likely some of the decaying material is the mulch. The other question I get regarding mushrooms is are they edible.  I do not feel comfortable telling someone to eat mushrooms from their landscapes. There are knowledgeable people who have made mistakes in identification so do not take this on yourself. In order to be safe, purchase your edible mushrooms from a grocery store. Please.   

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Rebecca L. Jordi
Nassau County Extension Director
UF/IFAS Environmental Horticulture 
543350 U.S. Highway #1
Callahan, FL 32011
904-530-6351

Also visit Nassau County Extension website.