Weekly Home Horticulture Column
Q. The landscape company that takes care of the property where I live has done it again. They have created these giant mounds of mulch under the bases of the trees in the common areas. I know this is not a good practice for the health of the tree. Can you tell me why?
A. Mulching under trees is a common practice to help retain soil moisture, keep weeds at bay and to create a buffer zone from maintenance equipment. Sometimes the only thing that does well underneath the shade of a tree is a 3-inch layer of mulch. But mulch applied too thickly can be a detriment to the tree. Thick mulch, or volcano mulching, can really stress the tree and shorten its life span. Too much mulch (in excess of 4 inches) over the tree's rootball can intercept water that should have reached the roots. Because of this, the UF/IFAS recommendation is to keep mulch about 12 to 15 inches from the trunk of the tree. This allows water to freely enter the rootball and keeps the mulch from resting on the trunk. Mulch resting on the trunk can trap moisture there and begin to rot the trunk. Roots from the tree will grow up into the thick mulch causing stem-girdling roots. Girdling roots ultimately can kill the tree. A 3-inch layer of mulch is all the mulch you need to put around the tree, and it can go out as far as the drip line of the tree canopy. For more information about proper mulching and other Florida-friendly landscaping tips, visit the UF/IFAS Extension website www.solutionsforyourlife.com.
Q. I have two bamboo plants with mites on the bottom of the leaves. The leaves are speckled green and yellow. Can you recommend the best pesticide to use on these critters, and any other recommendations? I was thinking about removing some of the good portions of the leaves. What do you think about that?
A. There are a few types of mites that can get on your bamboo plants. I am not certain which one you are having troubles with, but often it is a spider mite type that causes speckling of the leaves. You will need to use a 10x magnifying glass to see the mites. If you see loose webbing associated with the damage that is the area to start looking. Look for an eight-legged critter that is 1/60th of an inch in size. At that size you know they are hard to see with the naked eye. Oil sprays are recommended to break the life cycle of the mites. A product like organocide or horticultural oil will help with minor infestations. If your mite problem is out of hand, with lots of damaged leaves, you may need to use a miticide product like Avid to bring it under control. Removing leaves/canes will promote new growth, but you will have to spray the regrowth to bring the mites in check. Often times, mites come in from infected plants. It is a good idea to quarantine new plants before introducing them to your collection. For more information, contact the Alachua County Master Gardeners at 352-955-2402.
Q. My peach tree is in full bloom, and there is a lot of winter left. Will these flowers make it through the cold?
A. Peach trees bloom following a dormancy period and an accumulation of chill hours. Chill hours are hours below 45 degrees. Most of the peach varieties recommended for North Central Florida have chill hour requirements between 300 and 500 hours.
If your peach tree has a lower chill hour requirement, it accumulated the chill hours for the year, and after a few weeks of warm temperatures, it was ready to break bud or flower. In the Gainesville area, our average chill hours per year are 400 to 500 hours. When you are selecting peach varieties, it is important to keep this in mind. Peach varieties, such as Gulfprince (400), Gulfcrest (350), UF 2000 (300), Flordacrest (350) and Flordaking (450) have chill hour requirements that are appropriate for North Central Florida and are recommended for backyard growers. Seek out these types of peaches from your local nursery.
Peach buds, flowers and fruits can be damaged by freezes. Buds can take temperatures as low as 18 degrees, though. Fully opened flowers can withstand temperatures in the high 20s with a slight percentage loss of fruit. Severe temperatures (low 20s for several hours) usually destroy the entire buds, flowers and seeds in the fruit, which causes the small fruits to drop off. Commercial growers often ice over their orchards to protect the flowers. In a backyard situation, it is better to cover the tree with a high-quality frost cloth and place incandescent light bulbs in the canopy, or string old-fashioned Christmas tree lights (the large bulbs that get warm when they are lit) in the tree. For more information about selecting the right variety of peach for you, call the UF/IFAS Alachua County Master Gardeners at 352-955-2402.
Q. My family's home has some tangerine trees that were planted back in the '70s. We've never pruned them, and while I've heard they don't need pruning, some of the branches are overburdened with fruit. They seem likely to break.
A. We are in the middle of citrus-picking season in North Central Florida. Backyard oranges, tangerines, lemons and grapefruit are having a banner year, thanks to last year's mild winter and good summer rains.
Generally, citrus only need to be pruned to keep the tree to a size that makes picking safe and easy. Also, having a tree that is under 15 to 20 feet makes maintenance activities easier. Some citrus, like tangerines, go into a biennial bearing cycle, meaning they have a bumper crop one year and a very light crop the next. Thinning young fruit during the heavy years can help to moderate the crops, but for gardeners, thinning is the hardest thing to do; we hate to see the fruits of labors hit the ground. My advice for you is to lighten the load as soon as you can because the branches can break under the weight of a crop.
Then in March, after the danger of frost, prune the upper branches down by one-third. The tree may be in flower when you are pruning, so you will be sacrificing some fruit from next year's crop. It will be worth it to have a tree with strong branches that is easier to pick.
The University of Florida/ IFAS extension website www.solutionsforyourlife.com has two great documents on growing citrus titled "Citrus Culture in the Home Landscape" and "Citrus Problems in the Home Landscape."
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Peach Tree Blooms