Sara Shields, Singh, Raghuwinder, Strahan, Ronald E., Fontenot, Kathryn, Kirk-Ballard, Heather
Get Your Soil Tested!
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You may have noticed some recent changes to our demonstration gardens as a result of the drainage project in and around the LSU-Alexandria campus. In an effort to re-establish the Louisiana Super Plant demonstration garden out front, we replanted from the Sorbet series of violas, one of our “go-to” cool-season annuals. Sorbet violas were added to the Louisiana Super Plant list in 2012 and have continued to perform wonderfully every year we have planted them in the demonstration gardens. The violas grow 6 to 8 inches high and about 1 foot wide and should be spaced about 10 to 12 inches apart. Best planted in full sun, these members of the violet family can be planted any time from fall through early spring and will continue growing into late April or early May and possibly later if we have a milder start to the summer months. Be sure to fertilize at planting and irrigate during times we are not receiving regular rainfall. With a little planning and care, these Sorbet violas can provide a nice pop of color in your landscape beds, containers or hanging baskets.
We hope you enjoy these winter months! If you have any gardening-related questions, please contact your local LSU AgCenter extension office.
Sara Shields, Ph.D.
Louisiana Master Gardener State Coordinator
Central Region Horticulture Coordinator
When I was starting out in professional forestry, I was a service forester in an urbanizing county in Virginia. One of the questions I frequently encountered was “What is the fastest growing tree for my landscape?” While this is still a common question, we generally recommend folks avoid planting fast-growing trees because they are more likely to be short lived and become maintenance headaches. In essence, fast-growing trees tend to have weak wood, so broken branches and tops would require heavy cleanup.
I still receive that question quite often in my capacity as county agent in Beauregard Parish. One tree that folks often inquire about is the water oak. The best description I have of water oaks is to think of them as the “teenagers of oaks” in that they have “issues.” According to Debbie Shaughnessy and Bob Polomski, of Clemson Cooperative Extension, water oaks have these problems:
I can affirm the observations of Shaughnessy and Polomski by virtue of site visits with homeowners. While water oaks can be good shade trees for the first 30 or 40 years, large water oaks tend to have broken branches and obvious cavities. When these compromised trees are near homes, improvements and parking areas, I consider them to be hazard trees and recommend their removal.
If you have a younger water oak, enjoy it while it is healthy and robust. Preventative pruning, such as training to a central trunk, keeping the main branches spaced at least 2 feet apart and avoiding making large pruning cuts, can help maintain the health of younger water oaks. However, as a water oak ages, keep an eye on it for damage, which will likely be a site for decay. If you have concerns about your water oak, contact your extension agent or extension forester and ask for a site visit to see if your aged water oak is becoming a hazard to your home.
Associate Extension Agent
Like most trees and shrubs in the landscape, pruning fruit trees should occur when the plants are dormant. While pruning fruit trees in the middle of January is not a suggested practice, early to mid-February is recommended for several reasons. For one, the average last frost date in this part of Louisiana is March 15, so waiting until February to start pruning decreases the chance for damage from a late frost. It is also best to wait and prune at a time when the tree can heal pruning injuries and not be so stressed. Pruning too early might encourage growth, especially if temperatures fluctuate significantly. This tender new growth could be severely damaged if we happen to get a late frost.
For young trees, it is typically better to wait until late February or early March, which gives the trees a chance to break bud. Pruning after the trees have broken bud will allow you to go through and assess which limbs are dead, diseased, decayed or otherwise damaged. Additionally, pruning fruit trees also eases harvesting by shaping and reducing tree height. Pruning will also increase flower production on trees that bloom on new growth, such as peaches. Proper pruning will also allow for more light to reach the fruit, in turn improving fruit color. Thinning the fruit crop later in the season will further improve the fruit quality by improving fruit size and sugar content.
It is important to follow proper pruning techniques when pruning fruit trees because different methods of pruning are used on different fruit species. The first step is to remove those dead, diseased, decayed and damaged limbs mentioned above. The branches should be cut back to a fork or bud, but be careful not to cut the branch collar, which is a ridge or area of wrinkled wood found around the base of the branch. The branch collar serves to heal nearby wounds, in which it quickly grows over the cut surface. You should not leave a stub sticking out of the collar because the collar will not be able to grow over the cut surface.
The next step is to remove the branches that grow toward the center of the tree. Branches crossing nearby limbs could cause rubbing injuries and should be removed. Additionally, removing these center branches will increase light penetration and air circulation to the center of the tree canopy. If there are any limbs of equal size that form a sharp “V” shape, one of the limbs should be removed before the limbs get very large to prevent splitting. Limb growth can be directed by pruning back to a bud or shoot that is pointing toward the direction where growth is desired.
Knowing the pruning process can help you assess each individual tree beforehand to decide which limbs need to be removed on each tree. The LSU AgCenter has informative publications on the issue. They are available both online and in your local LSU AgCenter extension office.
Sara Shields, Ph.D.
Louisiana Master Gardener State Coordinator
Central Region Horticulture Coordinator
Winter is a great time to get outside and get things done in the garden. We are very fortunate here in the South to have good weather during the winter months for gardening, and it is an excellent time to plant trees and shrubs in the landscape.
Although deciduous trees and shrubs are in their dormancy, roots are still actively growing. Planting during December, January and February provides plants with several months to develop a strong root system before they put out a new flush of leaves and flowers in spring.
The structure of trees and shrubs in our lawns and gardens is very apparent this time of year. Dead branches, low-hanging branches and branches that cross one another are visible now and should be removed. Take this opportunity to trim your trees and shrubs. Removal will be much easier without the additional weight of leaves.
As retail nurseries begin clearing out Christmas trees and merchandise, they will be bringing in a new stock of woody trees and shrubs. Tropical plants will be available later in the warmer season when they are less likely to be damage by colder temperatures.
The National Arbor Day Foundation has started the Time for Trees initiative to highlight how “trees clean our air, protect our drinking water, create healthy communities and feed the human soul.” Founded by J. Sterling Morton in 1872 in Nebraska City, Nebraska, where an estimated 1 million trees were planted, Arbor Day is celebrated every year. In 2021 it will be celebrated in most of the country on April 30. On this day, individuals are encouraged to plant trees.
Louisiana celebrates Arbor Day on the third Friday of January. The LSU AgCenter Botanic Gardens at Burden will hold its annual Arbor Day event on Jan. 23 from 9 a.m. to 1 p.m. Free and open to the public, this event will feature educational talks on native trees given by experts from the LSU AgCenter. You and your family can plant a tree while there and get GPS coordinates so you can come back and visit “your” tree and watch it grow for generations to come.
When deciding what trees and shrubs to purchase and plant, it is best to sit down and consider the year-round interest of those plants. A great design will have beauty and interest in each season. That can include evergreen plants, flowering plants and deciduous plants that have excellent fall foliage change.
Evergreen trees and shrubs provide year-round greenery and are popular in almost every landscape design. Some good, large evergreen trees include live oaks (Quercus virginiana), Southern magnolias (Magnolia grandiflora), Leyland cypress trees (Cupressus × leylandii) and American holly trees (Ilex opaca).
The Southern magnolia has fragrant white flowers in late spring to midsummer, and in winter the female American holly trees sport gorgeous red berries that attract birds and other wildlife.
Some medium-sized evergreen trees are the Southern wax myrtle (Morella cerifera), camphor tree (Cinnamomum camphora) and red bay (Persea borbonia).
You can choose from several small evergreen trees with many different functions. Some have flowers and put on a display in the late fall into early spring. These include the camellia (Camellia japonica) and camellia sasanqua (Camellia sasanqua).
Other fragrant flowering trees include loquat (Eriobotyra japonica), banana shrub (Michelia figo) and sweet olive (Osmanthus fragrans). Other trees — including the Burford Chinese holly (Ilex cornuta ‘Burfordii’), yaupon holly (Ilex vomitoria) and eastern red cedar (Juniperus virginiana) — provide ecosystem services such as wildlife food.
Compared to evergreen trees, deciduous tree have a much larger selection for use in Louisiana. Some large deciduous trees with good fall foliage change that are also great as shade trees for the landscape are American beech (Fagus gramdifolia), bald cypress (Taxodium distichum), basswood (Tilia americana), pecan (Carya illionensis), tulip tree (Liriodendron tulipifera), sycamore (Platanus occidentalis) and cucumber magnolia (Magnolia acuminate).
Some outstanding small, spring-flowering deciduous trees are the fringe tree (Chionanthus virginicus), flowering dogwood (Cornus florida), Taiwan cherry (Prunus campanulata), saucer magnolia (Magnolia X soulangiana), parsley hawthorn (Crataegus marshallii), redbud (Cercis Canadensis) and silverbell (Halesia diptera).
Other deciduous trees with outstanding fall foliage change are the American hornbeam or ironwood (Carpinus caroliana), hop-hornbeam (Ostraya virginiana), swamp red maple (Acer rubrum Drummondii), Japanese maple (Acer palmatum), southern sugar maple (Acer barbatum), green ash (Fraxinus pennsylvanica), sweetgum (Liquidambar styraciflua), Chinese pistache (Pistacia chinensis) and many oak species, such as shumard oak (Quercus shumardii), nuttall oak (Quercus nuttallii), white oak (Quercus alba) and post oak (Quercus stellata).
Planting trees is a great way to leave a lasting legacy for generations to come to enjoy. In my humble opinion, trees are the key to combating climate change by conserving energy, sequestering carbon and reducing the overall concentration of greenhouse gases in the atmosphere.
Consider this proverb: “The best time to plant a tree was 20 years ago. The second-best time is now.”
Heather Kirk-Ballard, Ph.D.
Consumer Horticulture Specialist
Heather Kirk-Ballard, Ph.D.
Consumer Horticulture Specialist
Let’s make the most of December’s garden and start the New Year off right by following best management practices to get the most out of our fruit and veg crops.
December is the last month I think of as actual winter. January and February to me are very early spring. So, in this last month of winter here are a few to-do items to help keep the garden active!
Kathryn “Kiki” Fontenot, Ph.D.
LSU AgCenter School of Plant, Environmental and Soil Sciences
Most lawns should be dormant or at least close to this stage by Christmas. Because lawns are not actively growing, fertilizer applications are not needed during the winter. Most lawn fertilization for growth should have stopped on home lawns by late summer (late August to very early September for St. Augustinegrass and centipedegrass).
Nitrogen fertilizer on dormant to semidormant St. Augustinegrass, centipedegrass and zoysiagrass lawns can lead to increased brown patch and winter kill. Also, nitrogen applications during this time have a greater potential for leaching or movement into nontarget areas.
I’m a big believer in soil testing. If your lawn did not perform well last growing season or you just want to get a quick check on soil pH, get the soil tested. Winter is an excellent time to collect soil samples and submit them for analysis.
Samples should be a composite of soil collected from 3 to 4 inches deep at various places around the lawn. Mix well and reduce the sample to about a pint of soil and take it to the LSU AgCenter Extension Service office in your parish or to a participating garden center. Make sure to specify the type of grass you are growing on the soil test form.
Soil samples submitted to the LSU AgCenter result in a wealth of information concerning the overall fertility of your soil. If results of the soil test indicate the soil pH is too acidic, lime will be prescribed in the soil test recommendations. Sulfur may be prescribed for soils that are too alkaline. Winter is the best time to apply lime or sulfur so that it can be activated by for the growing season next spring and summer. The correct soil pH is extremely important and has everything to do with nutrient availability and fertilizer performance.
Postpone any permanent warm-season turfgrass seeding until next spring. Soil and air temperatures will be too cold for germination and growth.
Sod, such as St. Augustinegrass and centipedegrass, can be laid during winter and established successfully during the spring. But remember to maintain good moisture to prevent the sod from dying. Establishment of sod is easiest, however, when sodding is delayed until the middle of spring, well after spring green-up.
Large patch disease can come and go throughout the winter if the weather is mild. Treatment with fungicides containing myclobutanil, propiconazole, pyraclostrobin, and triticonazole and azoxystrobin will reduce the spread of large patch. Damage from large patch will slow spring green-up, and diseased areas will remain unsightly until warmer spring weather conditions help with turfgrass recovery. These diseased areas become more prone to weed infestations.
Broadleaf weeds, such as clover and lawn burweed (sticker weed) and annual bluegrass infesting St. Augustinegrass, centipedegrass and zoysiagrass and dormant bermudagrass, can be suppressed with a late fall followed by a winter application of atrazine herbicide. The window for these atrazine applications is from October to early March. Herbicides containing a three-way mixture of 2,4-D plus dicamba plus mecoprop (trimec-type herbicides) can be used for winter broadleaf control on the same lawns that were sprayed with atrazine. MSM (metsulfuron) works well on lawn burweed and is highly effective on clovers and false garlic. Weed-and-feed products can be substituted as your first application of fertilizer during the early spring.
When it comes to managing lawn burweed specifically, don’t wait until the stickers show up in April to treat. It’s too late then. Spray burweed in early November with products mentioned previously. Repeat these applications in February and March.
Lawns may show signs of green-up in southern Louisiana in late February. Do not push turfgrass growth with fertilizer at that time! Fertilizer applied too early will feed winter weeds and will result in lush turfgrass growth that is more susceptible to injury from late frosts and increased levels of large patch disease. Lawns may be fertilized in the New Orleans area by late March, but delay fertilizing central Louisiana lawns until April. Consider fertilizing lawns in north Louisiana around mid-April.
Ron Strahan, Ph.D.
Turfgrass and Weed Science
Sooty molds are a result of nonplant pathogenic fungi that grow superficially as a thin black layer on leaves, fruit, twigs and stems of various crop plants or trees. The fungi grow on the honeydew produced by insects with piercing-sucking mouthparts. The insects, including aphids, leafhoppers, mealy bugs, psyllids, scale insects and whiteflies, pierce the plant tissue with their stylets and feed on plant sap. While continuously feeding, these insects ingest a large volume of sap fluid into their bodies, which is not entirely digested. After extracting nutrients from the sap, these insects excrete excess water and sugars from their bodies in the form of a sticky, sugary substance called honeydew. Most of the time, these insects feed on young, tender new growth and the honeydew drops below on all plant parts, including leaves, fruit, twigs and stems. Additionally, the honeydew covers understory vegetation, concrete surfaces, sidewalks, furniture, parking lots, etc., under host plants infested by sap-sucking insects.
Sooty molds are saprophytic fungi with dark, powderlike spores that break down honeydew. Abundance of sooty molds lead to formation of a thin, black layer. There are several species of sooty molds, but the most common ones are Capnodium spp. and Fumago spp. Sooty molds do not directly affect the host plant on which they reside but can inhibit the photosynthetic ability of the plant by covering leaves, twigs, fruit and stems. Under extreme conditions plants entirely covered with sooty mold may lose vigor and be predisposed to other plant pathogens. Plant growth may also be retarded, and yields can be significantly reduced. The aesthetic value of the plants covered with sooty mold is greatly reduced.
All plant species that are hosts for sap-sucking insects with the piercing and sucking type of feeding are affected with sooty molds. Some of the common landscape plants heavily affected by sooty mold are azaleas, camellias, citrus, crape myrtles, magnolias, oleander, pears, pine, roses, sago palms and viburnum. Hedges, small bushes or other plants, such as boxwoods, Indian hawthorn and ground covers, get sooty mold if the trees under which they are planted are infested with these insects. This happens when the honeydew from insects high in the canopy of trees drops on the vegetation underneath.
Managing sooty molds is very simple. Keep insects, such as aphids, mealy bugs, scale insects and whiteflies, in check. Once the insect problem is solved there will be no new sooty mold occurrence. The existing sooty mold infestation dries out after some time and easily sloughs off the infested areas.
Pressurized water can be used to wash off the sooty molds. Care should be taken while using pressurized water because it may damage the plant parts.
Insect infestations are generally controlled with insecticides, insecticidal soaps or horticultural oils. Before applying any kind of chemical pesticide, it is very important to identify the insect properly. Samples of plants infested with insect pests may be taken to your extension agent for identification. Consult with your local extension agent on the use of chemicals for managing insects. The LSU AgCenter Plant Diagnostic Center is also available to diagnose your plant health problems.
Raghuwinder (Raj) Singh, Ph.D.
Horticulture Pathology Extension Specialist