Horticulture Hints Winter 2018

Jeb Fields, Sexton, Mary, Singh, Raghuwinder, Strahan, Ronald E., Himelrick, David G., Fontenot, Kathryn  |  11/16/2018 6:25:21 PM

The LSU AgCenter recommends planting Louisiana Super Plants to brighten up your cool-season landscape

Now is the time to plant cool-season color in Louisiana landscapes. Louisiana Super Plants are rigorously tested to ensure a top-quality plant for your home garden.

Sorbet violas can be grown in full sun or part shade and will provide a rainbow of colors throughout the fall and potentially into the spring. Space them about 10 to 12 inches apart and enjoy the fantastic color. We really like the purple and gold ones!

Louisiana’s most landscape-durable petunia is Supertunia Vista Bubblegum. These can be planted now — or you can wait until later in the winter — to provide fantastic bubblegum color to any landscape. Also, try them in hanging baskets for an extra bit of pop.

Fall is a great time for ornamental edible landscape plants, and Redbor kale is no exception. Used as a bed liner or a focal plant, this purple-colored kale is a fantastic performer in the landscape that will surely impress.

Amazon series dianthus, Swan series columbine and Camelot series foxglove are all fantastic cool-season color options for fall planting to brighten up the garden.

For more information about these and other Louisiana Super Plants, please visit http://www.lsuagcenter.com/superplants.

Winter Protection of Landscape Plant Materials

Freezing temperatures can be very harmful to many of our landscape plants. However, there are a few steps you can take to help protect your garden from a freeze.

Move plants inside

If at all possible, move plants in containers inside the house. Even an external space, such as a garage or shed, will provide some insulation and, if connected to the house, will often get plenty of radiant heat to keep plants safe. If you do not have any room inside, try moving potted plants next to the house to get some added warmth from the walls.

Mulch

A fresh layer of mulch will provide added insulation for the landscape root systems. If possible, mulch up to the stem to provide as much coverage and insulation as possible. Mulch can also be applied to the surface of container plants for a bit of extra protection.

Cover

Covering plants is one of the easiest and best ways to provide additional freeze protection. Low-growing bedding plants and ground covers can be blanket-covered with fabric or plastic. Container plants should be grouped together and blanket-covered. Make sure when that the cover reaches the ground. The root system is what must be protected — not the foliage. If a cover is draped over the top of a shrub or tree but does not completely touch the ground, all the soil warmth will be lost. If you cannot completely enclose the plant, it is better to wrap the covers around the base of the plant like a mulch blanket than to drape it over. Make sure to remove the cover when above freezing and during the day to let the plant get sunlight. It is fine to leave a cover on for a few days if needed, but remaining covered for too long can have detrimental outcomes.

Remember, the goal is to keep the root system insulated as opposed to just the foliage. If possible, place some soil or heavy material at the base of the cover to hold the sheet or plastic to the ground to create a heat seal. Take additional care to ensure you do not break any branches. Also, container-grown plants are more susceptible to freezes than landscape plants because the root system does not have the soil as an insulator.

Watering

Make sure you water prior to a freeze if the soil is dry. Freezes often are accompanied by dry winds, which can dry plants out.

Pruning

Pruning should be ceased near freezes. Pruning generally pushes for new growth to start, which is susceptible to cold temperatures. Hold off the urge to prune poor-looking plant materials directly after freezes as well. Often it will take many days, weeks or even months to assess true winter damage! Scratch the stem lightly with a knife or even your fingernail. If there is green tissue underneath, the branch is alive.

For more information regarding your specific region, please contact the local horticulture extension agent for your parish.

Dr. Jeb S. Fields, Ornamental Horticulture Specialist

Gardening in the Winter

Gardening not only provides you a form of exercise — it also increases the number of fruits and veggies in your refrigerator! Instead of a New Year’s resolution to make a healthy change in January, start in December by ending one year and beginning the next year on a great garden note!

Monthly Garden Tips

December is the last month I think of as actual winter. January and February to me are very early spring. In this last month of winter, here are a few to-do items to help keep the garden active!

December

  • Scout lettuce, strawberries and all cole crops for insects. Aphids, slugs, snails and worms tend to cause problems in the winter garden. Insecticides such as horticulture oil, insecticidal soap and bifenthrin products — Ortho Bug B Gon Max, for example — work great for aphid control. Insecticides that kill worms and loopers include Sevin, Bt (DiPel is a well-known brand) and spinosad. Snails and slugs are best controlled with baits. Early evening is when these pests feed. You want the baits to smell strongly, so apply baits in the early evening for best results.
  • Plan on planting potatoes? Till and hip rows in the garden now. Early January can be very wet.
  • Plant onion sets. Choose sets that are thin — the size of a pencil or thinner. Thicker plants tend to bolt in cold weather and set seed rather than form a bulb.
  • Cover blooming strawberry plants when temperatures drop below 32 degrees Fahrenheit. Plants not in bloom? No need to cover.
  • Order spring vegetable seed now if you want first pick of the great varieties. Wait too long and other gardeners will order all the good varieties.

January

  • Onions can be planted from mid-December to early January. In early January, continue to plant onions sets. Bulbing onion varieties that perform well include Texas Grano, Mr. Buck, Texas 1015Y, Pinot Rouge, Red Burgundy and Miss Megan.
  • Mid-January through end of February: Transplant broccoli, cabbage, cauliflower, chard, kale and lettuce.
  • Mid-January: Plant Irish potatoes into the garden. Cut the potatoes a few days before planting. Cut larger potatoes in quarters and smaller potatoes in half. This larger size helps reduce rot.
  • Vegetable growers in south Louisiana should start their tomato, eggplant and pepper transplants mid-January. North Louisiana vegetable growers should wait until the end of January or the beginning of February. It takes between eight and 10 weeks to germinate and grow into decently sized tomato, pepper and eggplant seedlings for the garden. Keep seedlings in a warm and BRIGHT area. One week prior to transplanting, move the seedlings outside to harden off.

February

  • Continue to transplant broccoli, cabbage, cauliflower, chard, kale and lettuce transplants into the garden. Successive planting —adding a portion of a row or a new row — every two weeks ensures a steady harvest.
  • Direct-seed beets, turnips, mustard, parsley, radishes, lettuce, snap beans and Irish potatoes.
  • Leave space for spring crops, which will go into the garden in March and April.

Dr. Kathryn Fontenot, Vegetable Crops Specialist

Create a Festive Wreath With Local Plants

Collecting your own materials for a wreath during the holidays can be a fun and rewarding experience. Wreaths can be as simple or elaborate as you like. Look around your yard to find inspiration and collect a variety of cuttings. Try to find plants with different shades of green leaves and incorporate several different types of plant material to make your wreath interesting. Aim for a 6-inch cutting. If a branch is too long or heavy, it may fall out of the wreath. You’ll need a pair of sharp pruners to make a clean cut.

Plant material choices that are easily found in Louisiana include holly, magnolia, juniper, camellia, smilax, nandina, boxwood, eucalyptus or pine. Magnolia leaves are an excellent choice because their leaves are green on the top and soft brown on the bottom.

Use small branches with leaves attached to build the foundation of your wreath. Also look for shrubs with berries to add accents of color. Hollies, beautyberries and pyracantha bushes are all producing berries this time of year. Don’t forget to include herbs, such as rosemary, which will add a nice fragrance. Consider using a small poinsettia bract for a pop of color.

After cutting the twigs, immediately submerge the base of the cutting in a bucket with a few inches of water. This will ensure your trimmings won’t dry out before you assemble the wreath. Add texture by using pine cones, acorns or burlap. Dormant vines such as wisteria or grape can be a creative addition. The vines won’t have leaves, but their branches can be contorted or twisted and will make an interesting addition. Tuck your cuttings into the wreath base and fasten with floral wire if needed. Keep the wreath on an outside door. Inside air is too dry and hot and will cause the leaves to drop prematurely.

Mary Sexton, Extension Associate

Jujube and Loquat: Two Uncommon Fruit Crops for Louisiana

Jujube –

Scientific Name: Ziziphus jujube

Overall Ease of Care Ratings

Insect and disease pest control: Easy

Weed control: Moderate

Climatic adaption: Good

Pruning and training: Easy

Pollination requirements: Self-fertile

Chilling requirement: 200-400 hours

Adaption to hot/humid conditions: Good

Cold hardiness: Good

Site and Soil Requirements: Jujubes are native to China but have been grown in the U.S. for well over 100 years. Jujubes do best if planted in full sun. Jujube will do well in very hot weather and are tolerant of most soils. The trees need good drainage. They can grow in soils with high salinity or high alkalinity.

Irrigation Requirements: Plants are drought-resistant. Young plants will benefit from watering during extended drought periods.

Plant Spacing and Mature Canopy Size: Jujubes should be set out 12 to 15 feet apart because they require high light intensities for good production. Trees grow 20 to 25 feet tall. Trees produce many shoots that arise from the roots, so they can become weedy if allowed spread. Allowing plenty of room to mow around the tree will help in controlling unwanted suckering.

Years to Bearing: Two to three.

Potential Yield: Up to100 pounds on mature trees.

Planting Stock: Bare-root dormant nursery plants are usually available from November to March.

Varieties: Li and Tigertooth. GA-866, Sugarcane, Big Jim, Sherwood. Additional varieties for fresh use are Honey Jar, Shanxi Li, and Chico. Good drying varieties include Lang, Li and Shanxi Li.

Establishment: Jujubes prefer a soil with a pH of 5.5 to 6.5. Dig a hole wider than it is deep. Never plant a tree below the soil line visible on the trunk marking the previous soil level. Water the hole so the water penetrates deeply. Set the tree in the hole and back fill. Water it in thoroughly again.

Pruning and Training: Pruning is seldom needed on jujubes, because the trees have an open, upright growth habit. Pruning is not recommended for jujubes other than to remove dead limbs and clean up the lower branches. Any suckers coming from below the graft union should also be removed. Jujubes usually produce numerous thorny root suckers. These root suckers need to be removed promptly to prevent the tree from becoming weedy.

Fertilization: Jujubes appear to do well with little or no fertilization. Light broadcast applications of a balanced fertilizer during the growing season will speed growth.

Harvesting: The plum-sized fruit has a thin, edible skin surrounding white flesh. The single hard stone contains two seeds. When the fruit is brownish-green, it is like a mealy apple in texture and flavor. However, when fully dehydrated in a shriveled brown condition, the fruit is much better tasting and very similar to a date. Many people prefer them during the interval between the yellow-green stage and the full red stage. At this stage the flesh is crisp and sweet, reminiscent of an apple. Under dry conditions jujubes lose moisture, shrivel and become very sweet (20 percent natural sugars). If the fruit is picked when too green, it will not ripen. The fruit on a jujube tree does not ripen all at once, which allows harvesting over a long season.

Weed Control: Good weed control is essential.

Major Insect Pests: Jujubes have few insect pests.

Loquat

Scientific Name: Eriobotrya japonica

Overall Ease of Care Ratings

Insect and disease pest control: Easy

Weed control: Moderate

Climatic adaption: Fair

Pruning and training: Moderate

Pollination requirements: Cross-pollination

Chilling requirement: None (evergreen)

Adaption to hot/humid conditions: Good

Cold hardiness: Good

Site and Soil Requirements: The loquat is a favorite landscape tree in southern Louisiana. The loquat is colloquially referred to as a Japanese plum. Loquats are adapted to a subtropical to mild-temperature climate. Loquat trees are very cold tolerant and may withstand temperatures down to 8 degrees to 10 degrees Fahrenheit. Temperatures above 95 degrees Fahrenheit may negatively affect loquat tree growth. Where the climate is too cool or excessively warm and moist, the tree is grown as an ornamental but will not bear fruit. The loquat is a large evergreen shrub or small tree. Loquats are easy to grow and are often used as an ornamental. Their boldly textured foliage adds a tropical look to the garden and contrasts well with many other plants. Loquats are wind tolerant and grow best in full sun, but also do well in partial shade. They grow well on a variety of soils but need good drainage.

Irrigation Requirements: Loquats are drought tolerant but respond well to irrigation. They will not tolerate continuously wet ground.

Plant Spacing and Mature Canopy Size: The tree can grow 20 to 30 feet high but is usually much smaller than this at about 10 feet. Loquat trees not pruned may grow moderately large and should be planted 25 to 30 feet or more away from structures, electrical lines and other trees for best production. Trees that are pruned to limit their size may be planted slightly closer. Trees planted too close to other trees or structures may not grow normally or produce much fruit because of shading.

Years to Bearing: Three.

Potential Yield: Mature loquat trees may yield from 35 to 200 pounds per year depending upon tree size and care. The new flowers and fruit are often destroyed by freezes if temperatures fall below 27 degrees Fahrenheit. Because of their early blooming habit, they seldom fruit in colder areas unless they are in a protected location. In northern parts of the state, plant loquats in a protected location where at least half the day receives sun. Good choices are on the south side of a heated building and under tall pines.

Planting Stock: Two-year-old container plants.

Varieties: Loquat fruits grow in clusters, are oval, rounded or pear-shaped, 1 to 2 inches long with a smooth or downy, yellow, orange or sometimes red-blushed skin. The succulent, tangy flesh is white, yellow or orange and sweet to subacid or acid, depending on the cultivar. Each fruit contains three to five large brown seeds. The loquat is normally pollinated by bees. Some cultivars are self-infertile, and others are only partially self-fertile. Flowers of the early and late flushes tend to have abnormal stamens and very little viable pollen. There are numerous loquat varieties. Loquat varieties have a range of peel and pulp colors as well as flavors. Most loquats obtained from nurseries are seedlings and vary in fruit quality. Fruit from seedling trees are sweet but may be small. Several improved varieties are available, but these are hard to find and can usually be found only at nurseries that specialize in exotic fruits. Big Jim and MacBeth are two varieties that have done well in south Louisiana. The varieties Oliver and Premier have had fire blight problems in south Louisiana. Most loquat varieties are self-pollinating, but a pollinator variety improves fruit set. Champagne and Advance are reported to be self-infertile. Gold Nugget, Thales and Tanake are additional varieties that could be tried on a trial basis. Other varieties include Emanuel, Golitch, Juda, Judith, Oliver, Sherry, Thursby, Bartow, Fletcher Red, Hardee and Wolfe.

Fertilization: Loquats benefit from regular, light applications of nitrogen fertilizers, but too much nitrogen will reduce flowering. Administer two small applications of a complete fertilizer per year during the period of active growth. Do not apply any nitrogen-containing fertilizer after August because this may induce the tree to continue to grow during the winter and therefore reduce flowering in the spring.

Pruning and Training: Loquats grow best in full sun but also do well in partial shade. Loquats also make attractive espaliers. Judicious pruning should be done just after harvest, otherwise terminal shoots become too numerous and cause a decline in vigor. The objective of pruning is a low head to facilitate fruit thinning and harvest. Prune also to remove crossing branches and thin dense growth to let light into the center of the tree. Loquats respond well to more severe pruning.

Cold Protection: Well-established trees can tolerate a low temperature of 12 degrees Fahrenheit. The killing temperature for the flower bud is about 19 degrees, and for the mature flower about 26 degrees. Fruit are set in the fall and mature in the spring. Winter temperatures below 25 degrees usually destroy the fruit.

Harvesting: Loquat fruits should be allowed to ripen fully before harvesting. They reach maturity in about 90 days from full flower opening. When ripe the fruit develops a distinctive color, depending on the cultivar, and begins to soften. Unripe fruits do not ripen properly off the tree and are excessively acidic. Under most conditions, the loquat tends to develop an alternate-bearing pattern, which can be modified somewhat by cluster thinning in heavy production years.

Weed Control: Because of the shallow root system of the loquat, care should be taken in mechanical cultivation not to damage the roots. Wood chips or similar materials can be used effectively in a 2-to-6-inch mulch layer around the loquat tree. Keep mulch 8 to 12 inches from the trunk to prevent rotting of the base of the tree.

Major Insect Pests: Loquats have few pest problems. Scale, fruit flies and birds can be a problem.

Major Disease Pests: Fire blight (the same bacterial disease that attacks apples and pears). Pruning out diseased limbs often gives adequate control. Do not fertilize heavily because that can increase fire blight damage. Phytophthora can cause crown rot and Pseudomonas eriobotryae can cause cankers.

David Himelrick, Fruit Specialist

Winter Turfgrass Management

Bleak Time for Turfgrasses Begins in December

December begins a bleak time for warm-season turfgrasses. 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. Actually, you should have stopped nitrogen fertilization on home lawns by late summer — late August to very early September for St. Augustine grass and centipedegrass.

Nitrogen fertilizer on dormant to semi-dormant St. Augustine grass, centipedegrass and zoysia 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.

Soil Sampling and Liming

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 the soil well, 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 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.

Turf Establishment

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. Augustine grass and centipedegrass, can be laid during winter and established successfully during the spring. 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.

Brown Patch Disease

Brown 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 brown patch. Damage from brown patch will slow spring green-up, and diseased areas will remain unsightly until warmer spring weather conditions help with turfgrass recovery.

Winter Weed Management

Broadleaf weeds, such as clover and lawn burweed (sticker weed), and annual bluegrass that infests St. Augustine grass, centipedegrass, zoysia, and dormant bermudagrass can be managed with applications of atrazine herbicide applied in February and March. These are good months to spray winter weeds because they are still actively growing and not producing seed. Also, herbicides containing three-way mixtures of 2,4-D plus dicamba plus mecoprop, such as the Trimec product, can be used for winter broadleaf control with less turf injury potential in all Southern turfgrasses this time of the year. Weed-and-feed products can be substituted as your first application of fertilizer during the early spring.

When to Fertilize Lawns

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 brown patch disease. Lawns may be fertilized in the New Orleans area by late March, but delay fertilizing areas north of Baton Rouge until early April. Consider fertilizing lawns in north Louisiana around mid-April.

Dr. Ron Strahan, Turfgrass and Weed Specialist

Citrus Canker

Citrus canker is a serious disease of all citrus species and is caused by the bacterium Xanthomonas citri subsp. citri. The disease is thought to have originated in Southeast Asia. Different strains of the bacterium occur in citrus-growing regions of the world, but the Asiatic strain is considered the most severe and widespread form of citrus canker.

Citrus canker is a highly contagious disease, and all citrus varieties are susceptible, but some varieties are less susceptible than others. Listed from the most susceptible to the least susceptible citrus varieties are grapefruit, trifoliate oranges, navel oranges, sour oranges, sweet oranges, lemons, satsuma oranges, tangerines, Mandarin oranges, king oranges, kumquats and Mexican and Key limes.

The bacteria cause symptoms on all above-ground plant parts, including leaves, fruit and twigs. Young expanding tissue is highly prone to infection, and as the tissue becomes mature and hardens off, it becomes less susceptible. Natural infection requires free water on the leaf surface to permit bacterial access through stomates or wounds. The pathogen prefers a temperature range from 68 to 86 degrees Fahrenheit but is active over a wide temperature range. Lesions appear at about 10 days to two weeks after infection.

Symptoms on leaves and fruit start as tiny raised blisters that expand and become tan to brown as the disease develops. Lesions are visible on both sides of the leaves, with water-soaked margins surrounded by yellow halos (Figures 1 and 2) that become raised and corky as they age. The pathogen forms raised, corky, crater-like lesions on the fruit (Figures 3 and 4).

Similar lesions are present on the twigs and leaf petioles, but the water-soaked margins may be reduced, and the yellow halos are absent. As the disease intensifies, defoliation and twig dieback occur, and severely blemished fruits drop prematurely.

The bacterium enters the host tissue through stomates and wounds. It is not carried by insects or other organisms, but the wounds caused by citrus leafminers may serve as infection sites (Figure 5).

Bacteria survive in old lesions, and under wet and warm environmental conditions they exude from these lesions and disperse short distances through windborne rain, lawnmowers, other landscaping equipment and people carrying the infection on their hands, clothing or equipment. Long-distance dispersal of citrus canker generally is attributed to human movement of infected or exposed citrus material and storms like hurricanes and tornadoes.

Louisiana residents are urged not to move any infected citrus plant material within or outside the state. Louisiana has a state quarantine that prohibits entry of citrus nursery stock from outside the state. Homeowners must buy citrus trees from certified Louisiana nurseries only.

If you believe your citrus trees have symptoms like those shown in this fact sheet about citrus canker, please do not take any samples or transport any part of the plant. Instead, contact the U.S. Department of Agriculture at 225-298-5410 or the Horticulture and Quarantine Division of the Louisiana Department of Agriculture and Forestry at 225-952-8100. More information about citrus canker can be obtained by calling Dr. Raj Singh with the LSU AgCenter at 225-578-4562 or emailing rsingh@agcenter.lsu.edu.

Raj Singh, Plant Pathologist


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