Marcia Mathews, Singh, Raghuwinder, Strahan, Ronald E., Fontenot, Kathryn, Kirk-Ballard, Heather
Get Your Soil Tested!
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Here in the ArkLaMiss, winter months are the perfect time to install trees and shrubs into your landscape so they will be less susceptible to transplant shock. Plus, the soil is still warm enough to allow the root system to expand and become well-enough established for spring bud break.
As with any horticultural endeavor, careful planning before planting will ensure a healthy tree or shrub for years to come. First, have the soil tested to ensure pH and nutrient levels are where they need to be for the species to be planted. Azaleas, blueberries, camellias and gardenias, for example, will need a more acidic soil (a lower pH) than most other species. Soil test results from the LSU AgCenter should include instructions on what to amend your soil with.
Taking time to prepare a good planting hole will pay dividends in years to come. Underground roots are positively geotropic. That is, they will automatically grow downward, toward Earth’s center. Focus on the width of the planting hole instead of depth. Make the hole two to three times wider than the root ball or, if a potted tree or shrub, the pot. This will give roots plenty of room for growth and expansion. Some sources say to build a mound of soil in the center of the planting hole to set the tree or shrub on. If your soil has good drainage, this isn’t necessary. If you’re planting bare-root trees or shrubs, building a mound of soil in the hole is a good idea as it will encourage roots to start growing outward. If you’re planting grafted trees, make sure the graft union is above soil level.
LSU AgCenter Northeast Research Station
What are heirlooms? These are our old-time favorite flowers that are passed down from generation to generation by seed, division or simply by existing undisturbed in a landscape over the years. Perhaps you remember the hollyhocks growing along the wall of your grandmother’s house or the Johnny-jump-ups bordering the flowerbed of your childhood home. These plants embody the nostalgia of days gone by but not forgotten. You can keep these plants going along by reintroducing them to your landscape. Not only do they perform well in our area, having survived years or even centuries of cultivation, but they also add great beauty to our outdoor spaces. Here are some cool-season heirlooms to plant this winter in your cottage gardens and mixed borders for a uniquely Southern appeal.
Bachelor’s buttons, also known as cornflower, are native to Europe and have been around for centuries. They have since become naturalized, growing wild in some north Louisiana parishes. Pick up just about any wildflower seed packet and cornflower is usually in the mix. They come in an array of blue, white, and pink blooms atop swaying pale green foliage. They grow to about 2 to 3 feet tall and look great in mixed borders and make excellent cut flowers. Seed packets of various colors, mixes and sizes are available in garden centers and can be sown in a full sun location in late fall to early winter. Bachelor’s buttons will bloom heavily through spring into early summer. Plants are very cold tolerant, surviving most frosts and freezes.
Nasturtiums are an old-time garden favorite. Introduced to the U.S. in the early 1800s, they are originally native to South America, where they grew as perennials. Now, they are grown as self-seeding annuals and are widely available in many growth habits and bloom colors to suit your gardening needs. The foliage and flowers make a spicy addition to salads, and the seeds can also be pickled and used much like capers. Plant nasturtiums in full sun to light shade. They perform quite well in poor soils, so little if any fertilizer is necessary. Nasturtiums look great as low borders or in mixed containers. Seeds germinate quickly usually within a week. Sow seeds in late winter to early spring. Plants will tolerate light frosts, but zone 8 can be susceptible to hard freezes.
Calendula, or pot marigold, is one of the oldest cultivated garden plants, dating back to the third century. It was brought to the New World with the first European settlers for its edible and medicinal uses. The flower petals were eaten or used to color cheeses. The leaves were added to soups and salads but could also be used in poultices to stop bleeding. Today, calendula is grown for its cheery daisylike blooms in an array of orange, yellow, cream and pink hues. Seed packets for the many varieties available can be purchased through garden centers or online retailers. Sow seed directly in the garden in a sunny spot in late fall or early winter. Due to their compact, upright growth habit, these plants make great fillers in mixed borders and flowerbeds. Calendula is very cold hardy, blooming faithfully until daily temperatures exceed 80 degrees Fahrenheit.
Snapdragons have a long history in the garden and for good reason. Brought to America by early settlers, snapdragons quickly became a widely popular garden plant for their colorful and unusual flowers. Children throughout the centuries have enjoyed pinching the flowers to make the petals snap open and shut like a dragon’s mouth, hence the common name. Available in many colors and growth and flowering habits that range from tall to dwarf and mounding to spiking, there is a snapdragon out there to meet your needs. Shop your local nursery or garden center in the fall for the best selection. Plant in full sun in the fall, placing tall and spiking varieties to the backs of beds, or dwarf and mounding types to the front as a border. Snapdragons are exceptionally cold tolerant, surviving the winter with ease into the spring, when it puts on show. Plants usually die back with the summer heat but can be grown as a perennial if planted in the right microclimate.
Chinese forget-me-not was introduced to the United States specifically for ornamental horticulture purposes in the 1920s. The dainty true-blue flowers of Chinese forget-me-not made it a favorite among early American gardeners. Its charming name, derived from various legends of love and devotion, added to its appeal. This species offers more ornamental value than its native relative, the woodland forget-me-not. Firmament is the most common and widely used variety and is usually included in wildflower mixes. Use fresh seed and sow twice as much to achieve the desired germination rates. Sow in full sun to part shade in the fall. Chinese forget-me-not is grown as a cold hardy annual that will reseed.
The Louisiana Super Plants collection offers several alternatives to these traditional heirlooms for your cool-season cottage garden. Camelot foxglove, Diamonds Blue delphinium, Sorbet violas, Jolt dianthus, Homestead Purple verbena, Supertunia Vista Bubblegum and Swan Columbine are all cultivars of tried-and-true heirloom plants that make perfect additions to any home landscape, cottage garden or flowerbed. These plants have been put to the test and are more widely available as transplants in most nurseries. Whether you use Louisiana Super Plants or go old-school with plants from seed, you are sure to have a show-stopping landscape with these cool season beauties of times gone by.
LSU AgCenter Northeast Research Station
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