_____GARDEN TALK _____
EDITOR’S NOTE: UF/IFAS County Extension Director for Nassau County and Horticulture Agent III, Rebecca Jordi addresses questions about landscaping and gardening in northeast Florida. She is also a University of Florida faculty member. _________
QUESTION: I heard you speak in one of your plant clinics about the problems of trees and shrubs being planted too deeply. You talked about removing the soil from around the root area. What I don’t understand is how you know when a tree is planted too deeply. HC
JORDI: Sir Arthur Conan Doyle’s famous character, Sherlock Holmes, would reveal the secret to his deductions and often he would be told how elementary and obvious his answer once the connection was shown. You will shortly see how easy it will be to determine when a tree or shrub is planted too deeply in the ground.
Trees should have a natural flare at the bottom of the trunk where the root structures are formed. A tree planted too deeply will look like a fence post rather than a tapering tree. Ah, that is elementary! Well, yes it is.
Research provided through the University of Florida by Dr. Ed Gilman has shown twig dieback, reduced branch and foliage growth occur on trees planted too deeply in the ground. The upper most root structures should be just at or slightly below soil level as too much soil on top of roots restricts oxygen to the roots. Restriction of oxygen to the root structures reduces the root’s ability to absorb necessary water and nutrients.
The best cure for trees planted too deeply is to remove the excess soil from the root area. Leave about 12-18 inches around the base of the tree with nothing but a few inches of soil. Then mulch lightly outside the area with 2-3 inches of mulch, preferably using organic mulch as your first choice.
For those of you whose soil is slightly alkaline your best choice of mulch is a pine product such as pine straw or pine bark. The next plant clinics will be held at the Yulee satellite office between 10am and 2pm on March 21, 2011 and April 4, 2011. Bring in samples of poorly performing plants, trees and lawn grass and we will provide strategies for bringing them back to better health. There is no charge for plant clinic sessions. Check out Dr. Gilman’s solutions for too deep planting.
QUESTION: My camellia flowers normally stay on the tree for a long period of time but a few of the flowers turn brown and drop off quickly. What is wrong? BD
JORDI: There are environmental reasons for browning of camellia flower petals such as cold temperatures, too much sun or severe wind exposure. However, there is a serious disease of camellias which can cause the flower petals to turn brown.
It is easy to distinguish the difference between the disease and environmental causes as the fungal disease causes the vascular tissue to be darker than the surrounding petal tissue. The first sign of the fungal disease will be spots on the petals but the spots soon spreads to the rest of the petal tissue and then to the center of the flower at which time it is called flower blight. As with any disease, the conditions for the pathogen (fungus) have to be perfect. Early spring rains often provide that perfect environment for the fungus, Ciborinia camelliae, to damage the petal tissue. Ultimately the entire flower turns brown and the flower usually drops within 24 to 48 hours. Only the flowers of the plant are affected.
The best management is sanitation. Remove all diseased flowers and especially those which have dropped off the tree. This fungus lives in the soil so it is best to remove and replace old mulch when the disease is detected in a camellia plant. Fungal soil drenches are available which will be absorbed by the roots and transferred to the rest of the plant helping to maintain long term control. Topical fungal sprays are also available which can be sprayed directly on the flowering portion of the plant. As always, please follow the directions on the label for best results.
QUESTION: What can you tell me about the plant called Coral Bells? CB
JORDI: I suspect you are referring to the perennial plant also called Alumroot, Heuchera sanguine, which produces a flower on a long, slender stalk in the spring but the flowers are short lived. However, the foliage on these lovely ground cover plants is outstanding ranging in color from deep purple to lime green. Heuchera must be placed in a shady site.
There is conflicting information regarding their cold hardiness zones which range from zones 4 – 9. This plant has been widely studied and has produced over 50 varieties – too many to list. With so many cultivars it is difficult to determine whether they all can survive our hot, humid summers. Therefore, it would be best to use this plant sparingly until it can demonstrate an ability to perform well in Northeast Florida. Peach Melba is one of the newer Heuchera plants being sold in our local retail garden centers as a “Proven Winner” with the label stating it is hardy in zones 8 and 9. For those wanting plants resistant to deer, Heuchera may be a good choice. The flower apparently also attracts butterflies and bees.
The plant reaches heights of about 2 feet with 1-2 foot spread. It looks as though it would make a great ground cover under trees as long as it did not receive too much sun. It also does not like soil too moist so be sure the area is well drained. It can also be propagated by seed.
Rebecca L. Jordi, County Extension Director
UF/IFAS Environmental Horticulture, Nassau County Extension
543350 U.S. Highway #1
Callahan, FL 32011
904-491-7340 or 904-879-1019