It’s Time for Spring Clean-up in the Landscape

By Pam Brown, Urban Horticulture Extension Agent

The end of February and into March brings much warmer weather and plants in our landscape start to spring forth with new growth. This is the time of year when we want to refresh the landscape by removing any damage that was caused by cold weather, cleaning up leaves and other plant debris that collected under plants during the winter, planting annuals for spring and summer, and applying a fresh layer of mulch.

Now is the time to look at those plants that were damaged by the recent freeze that we had in most parts of the county. Plants that lost their leaves should be sprouting now. Prune these plants back to healthy sprouting buds that are growing to the outside of the plant by making pruning cuts at a slight angle about ¼ inch above the bud. Some plants may be only sprouting from the base or roots of the plant and you will need to prune the stems back to this growth area.

Cleaning up leaves and other plant debris that have fallen to the ground and removing diseased leaves and fruit is perhaps the single most important thing you can do to manage many of the leaf-spotting, powdery mildew, bud and flower blight, and canker fungi. This is because many of these fungi overwinter on plant debris. When this fungi produces spores, wind, irrigation and rain can disseminate them to other areas of the garden or landscape. Camellias and azaleas are susceptible to petal blight causing the flowers to turn brown and rot prematurely. All fallen buds, flowers or petals should be removed from under the plants as soon as possible. On camellias especially, if buds or flowers turn brown on the plant, remove as soon as you notice them. Keep your trash can or bag near by to avoid carrying infected debris across the yard.

Contaminated tools can also contribute to the spread of disease. Tools used to prune plants infected with witch's broom, canker, gall and other diseases should be disinfected after each use by dipping the cutting surfaces in a solution of one part bleach to nine parts water. Rubbing alcohol (70%) from the drug store will also work and does not require diluting. Disease can also be carried from plant to plant on hands. So, it is very important to disinfect your hands or gloves. Wash hands well, or you may want to carry into the garden with you some of the gel hand sanitizer that is now available.

In perennial beds, remove old flower heads, stalks, and any diseased plant parts. Examine roses for dead canes and remove them. Examine the shrubs and trees in your yard for dead branches or branches that are crossing and rubbing other branches. Prune these branches out. Pruning paint is not recommended to cover wounds made by pruning cuts.

If you planted annuals in the fall, such as impatiens, snapdragons, petunias, or geraniums, you may want to prune them back a bit and add some balanced slow release fertilizer. Gazania, Marguerite Daisy, Marigold, Nicotiana, Pentas, Salvias, Dianthus, and narrow-leaf Zinnia are some good annuals to plant in March for color through spring and into the summer. Gaillardia is a really drought tolerant flower that can be seeded directly into the ground near the end of March that will give you drought tolerant flowers all summer long. If you have shady areas where you want some color; Caladium bulbs have wonderful leaf colors.

When all of your clean up efforts are finished, put down a fresh layer of mulch. Be careful to keep the mulch a couple of inches away from the base of plants and not more than two to three inches deep. It is not necessary to remove old mulch beyond raking up diseased leaves and plant debris. Old mulch continues to decay, releasing organic matter and nutrients into the soil.

Once you have finished with your clean up – spruce-up activities, you are then ready to sit back, relax with a glass of iced tea and enjoy your handiwork – until those first weeds start showing up. A beautiful garden takes a lot of work, but I think the results are worth the effort!

Controlling Crabgrass

By Jane Morse, University of Florida/IFAS Extension Agent, Pinellas County

If crabgrass has taken over your lawn, early February is the time to put out a pre-emergent herbicide. Pendimethalin (sold as Pendulum, Pre-M, Turf Weedgrass Control, Halts Crabgrass Preventer) provides excellent control of crabgrass and is safe at the recommended rate on mature, actively growing grass (Bahia, Bermuda, St. Augustine and Zoysia). Apply herbicide when daytime temperatures reach 65 to 70 degrees Fahrenheit for 4-5 days in a row, or usually about the same time that azalea plants start blooming in the spring. Plan to reapply herbicide about 2 months later for season-long control.

If weeds are a recurring problem in your lawn, follow these steps to have a healthy, thick lawn that will out-compete most weeds:

1. Start off with the right grass. Bahia is best suited for sandy, acidic soils that are subject to drought. St. Augustine is better suited for mildly acidic to alkaline soils that are subjected to salty conditions. Also choose grasses based on the amount of care that you are willing to provide. Bahia has a low maintenance level, St. Augustine a moderate level, while Zoysia and Bermuda have a high maintenance level. For areas of dense shade choose a shade-tolerant ground cover or use mulch.

2. Mow at the right height. Set those mower height adjustments high for St. Augustine and Bahia grass which should be mowed at a height of 3 to 4 inches. Dwarf St. Augustine grasses (Delmar, Jade, Seville) are mowed at 2 - 2 ½ inches. Bermuda is mowed at ½ to 1 ½ inches and Zoysia 1 - 2 inches. Proper mowing height and frequency will get rid of many annual weeds.

3. Mow often. Only 1/3 of the leaf blade should be removed each time the lawn is mowed. The shorter it’s mowed, the more often it needs to be mowed. Repeatedly removing too much of the grass blade (more than 1/3) will eventually kill the grass. Keep the mower blades sharp for the best cut. Mow when grass is dry.

4. Water only when it needs it. When 30% of the lawn starts to show symptoms of wilt (i.e. folded leaf blades, bluish-gray color, foot-prints that last for more than 10-15 minutes, and soil is dry), water the grass (unless rain is expected in the next day). Apply ½ to ¾ inch of water each time the lawn is watered. Overly wet lawns promote sedges, spurges and dollar weed, as well as root rots. When watered and mowed correctly the grass will develop a deep root system and will not require water as often. Water in the early morning when dew is still present. Watering late in the evening promotes disease development.

5. Fertilize correctly. Lawns that have been over-fertilized are much more prone to getting chinch bugs, brown patch, grey leaf spot, pythium blight, powdery mildew and thatch. Under-fertilized lawns are prone to getting take-all root rot, dollar spot and rust. Of course, if the lawn gets attacked by these insects and diseases, large areas die off, leaving a perfect place for weeds to sprout.

Fertilize St. Augustine two weeks after the start of spring regrowth using a complete fertilizer (16-4-8) containing slow-release nitrogen (e.g., Isobutylidene diurea [IBDU], Sulfur-coated urea [SCU], urea formaldehyde, cottonseed meal, or poly-coated sources). Sewage sludge products are also a slow-release nitrogen source, but avoid them if you have palms. Apply 1 pound of nitrogen to 1000 square feet of lawn (divide 100 by the first number on the fertilizer bag to get the pounds of fertilizer to apply per1000 sq. ft.) e.g. 6.25 pounds of 16-4-8 fertilizer per 1000 square feet. Apply ferrous sulfate or a chelated iron source in July. For Bahia grass apply a complete fertilizer with slow-release nitrogen in March and August and an iron source in May.

6. Scout. Watch turf closely for symptoms of disease or insect attack. Keep track of any problems on a calendar and note the location where symptoms first appeared. Knowing when to expect a certain disease or insect pest (i.e., chinch bugs, brown patch, etc.) will help to catch problems early before much damage can be done. Pest problems should be greatly lessened or non-existent when proper maintenance steps are used. Using these steps will lessen the need for pesticides, fungicides and herbicides and help to keep our environment clean.

For more information call the Extension Service’s Horticulture Help Line at 727-582-2110, visit our website at: pinellascountyextension.org; or visit the University of Florida Turfgrass website at turf.ifas.ufl.edu.

Pruning Crape Myrtles

By Pam Brown
Urban Horticulture Extension Agent

Crape myrtle (Lagerstroemia indica) is a small tree that prefers hot, sunny climates. It is well adapted to our climate here in Pinellas County. Once well established, these trees are extremely drought tolerant and have low fertilizer requirements. Crapes grace us with lovely blooms in the summer. And, if pruned or trained properly, the bare trunk and branches are very sculptural after loosing leaves in early winter.

The common practice of chopping off the tops of crape myrtles is a severe pruning practice that induces excess vegetative growth, promotes sprouting at the base of the plant, creates unnatural branch structure, and results in larger but much fewer flowers. Many prune this way because the plant is too large for the space where it is planted or they see their neighbor’s trees pruned this way and feel that this must be the correct way to prune. There is also the misconception that this type of pruning is necessary to promote blooming. In actuality, light corrective pruning is all that is needed.

The best way to assure that the crape myrtle that you have planted will not grow too large for the space provided is to choose a cultivar for the mature size it will become. There are dwarf, semi-dwarf, intermediate and tree forms of crape myrtles. The University of Florida/IFAS publication Crape Myrtle in Florida (http://edis.ifas.ufl.edu/MG266) lists cultivars by name, size, color of blooms, and disease resistance.

Flowers are produced on new growth and crape myrtles will bloom without any pruning. Pruning can produce blooms of larger size, but there will usually be fewer of them. Removing seedpods as they form during the summer can stimulate another flush of blooms before fall. Full sun is required for best flowering. So, crape myrtles planted in shade will not develop many blooms.

Pruning should be done in January or early February before new growth starts. To allow the plant to develop into the small graceful tree that it is destined to become, select one to several strong trunks originating from the ground and prune off any weaker remaining stems at ground level. As the tree grows, remove lateral branches to one-third or halfway up the plant. Also remove any branches in the developing canopy that are crossing or rubbing another branch. This will develop an open canopy, which allows air circulation that will discourage fungal disease. Any broken or dead branches should also be removed. All cuts should be made either to the trunk or to a side branch that is facing out from the center of the tree. These are called thinning cuts that should not produce a heavy flush of dense growth in the canopy. In addition, the sprouts (suckers) that grow up from the base of the tree should be pulled out while they are still green a succulent.

There are lovely examples of properly pruned crape myrtles in several locations on the grounds of the Florida Botanical Gardens.