Southeast - Spring 2022

Mary Ferguson, Singh, Raghuwinder, Strahan, Ronald E., Fontenot, Kathryn, Kirk-Ballard, Heather

LSU AgCenter Horticulture Hints for Southeast Louisiana Spring 2022 header.

Past Issues


Get Your Soil Tested!

Get your soil testedjpg

www.lsuagcenter.com/soiltestingkits


Never miss an issue of Horticulture Hints from the LSU AgCenter!

Visit the Horticulture Hints website at
www.lsuagcenter.com/HortHints

Then click on the Subscribe button!

A well pruned, tall crape myrtle tree next to a walkway, outside a brick building.
Properly pruned crape myrtles.

Pruning:
How, Why and When


We prune plants for a variety of reasons. Sometimes, we prefer or feel obligated to maintain a certain appearance, such as a raised canopy on a plant that naturally produces growth near the base or a small number of trunks on a potentially multitrunked plant.

Often, we prune because a plant was put in a place for which it eventually got too large — close to a house, under a window or power line, etc. This type of pruning is largely preventable by attention to mature plant size and placement prior to planting.

One reason to train young trees, particularly, is so they’ll have good structure and not have the narrow crotch angles and included bark that make branch attachments weak. If you’ve ever wondered why Bradford pear trees tend to break apart in storms, this is why.

Removing crossing limbs to prevent damage and removing already damaged or diseased parts of plants are other reasons to prune.

When it comes to fruiting plants, we may prune to make picking easier, to increase sunlight penetration and air movement, and to improve fruit quality.

There are several things to consider when deciding if, when and how to prune. One of the primary considerations regarding when to prune is flowering time and, relatedly, whether a plant flowers on new growth (the current season) or old growth.

Ornamental plants that bloom in the late winter and early spring generally bloom on shoots that grew in a previous season. Many of our azaleas, like the southern Indica hybrids (Formosa, George Lindley Tabor, etc.), are poster children for this. To avoid sacrificing blooms, these should be pruned after flowering.

I’ve been asked how late is too late to prune azaleas. The end of June or first of July are sometimes mentioned as a cut-off dates, after which flower buds are likely to be forming for the following year. However, I don’t know exactly when flower bud formation starts here in southern Louisiana. This stage of bud formation is something that happens within the plant — not something we can see on the outside of a branch.

Rather than putting off pruning until the end of the window, if you need to prune your azaleas, you should go ahead and do it soon after blooms fade. This gives plants more time to recover before weather gets hot.

Other plants that bloom on old growth and should be pruned soon, if needed, include camellias, primrose jasmine, Carolina jessamine and bridal wreath spirea.

Crape myrtles, chaste trees (vitex) and American beautyberry are examples of the opposite situation. They produce blooms on new shoot growth, so they can be pruned in late winter, while dormant, without removing flower buds.

Some groups have species with both types of plants. Among the hydrangeas, mophead or “French” hydrangeas generally bloom on old growth, although there are exceptions, such as the Endless Summer series. Mophead hydrangeas are unusual among the old-growth bloomers in that they bloom relatively late in the season. Oakleaf hydrangeas bloom on old growth as well, while panicle hydrangeas, like Limelight, bloom on new growth and can be pruned in late winter.

Many roses bloom on new growth, which is why they’re often pruned in late January or early February. There are some roses, though, that bloom once per year on old growth and should be pruned after flowering. These include the Cherokee rose and Lady Banks’ rose.

Mary Helen Ferguson, Ph.D.
Associate Extension Agent

A small circular planter with two types of plants. One is a trailing, cascading vine. The other is a plant with bright purple flowers located in the center of the pot.

Get Creative With a Colorful Container Garden


You don’t need a large yard or a lot of space to create a beautiful garden. You can create beautiful planters or containers that fit any space with limitless plant combinations that bring beauty and joy to wherever you call home.

There are plenty of options to choose from when it comes to the size, shape and color of containers and planters — hanging baskets, window boxes, small and large containers for combination plantings, single plant containers and clusters of pots. Your options for the plants themselves are plentiful and diverse, too.

To create a beautiful container design, begin by choosing a container that suits your spatial needs. Most garden centers, retail nurseries and online shopping venues offer many types.

Next, choose the plants and arrange them in a design of your choosing. Keep them looking good until you want to change the design.

One of the great advantages is that you can change these out. Year after year, you can play with the plant combinations, colors, textures and themes.

A combination planter typically has what is known as a filler, a thriller and a spiller. If you haven’t heard these terms yet, let me explain them to you.

The thriller is the plant that is main attraction of your container planting. It will be the focal point of your design. Choose a plant that has some height and a striking flower form or color.

The filler is just as the name suggests. Use these plants to fill in areas to create a fuller look in the arrangement. Fillers are medium-sized plants, typically in a mounded form, that make up the bulk of the plant material in the container. You can choose just one type of plant for focal impact, or you can choose several different plant types of similar sizes.

Spiller plants are the trailing, cascading plants that flow over the sides of the containers and complete the arrangement.

When choosing fillers and spillers, a good rule of thumb is to use an odd number of plants — three, five, and seven and so on.

Symmetry brings a good balance to beginning designs. Although it is not required to have an equal number of similar or identical plants on each side of the focal point, it does bring a visual balance to the arrangement.

Be sure you bring different textures into the container planting and design. Add fine-, medium- and coarse-leaved plants. Use tall pieces that bring height for the focal point; shorter, mounding species en masse; and low-growing spiller plants to soften the edges of the container planting.

Lastly, use proportional sizes to match the container. For large containers, use larger plants; use smaller plants in small containers. The rule of thumb is that the tallest plant should not be taller than 1 to 2 times the height of the container.

Now is the fun part: picking the plants. Be sure that you use season-appropriate plants. For example, if you are creating a design for the summer, make sure you are using heat-tolerant, warm-season annuals and perennials.

Most trees and shrubs will be fine throughout the seasons, but be sure to use evergreen selections unless you plan to rotate them out with the seasons as you do with your annuals and perennials.

A metal rectangular planter planted with a variety of plants.
You can use interesting container for an artistic flair.
A large planter filled with ornamental kale and violas are the outside of the planter and yellow and purple flowering types of snapdragons in the center.
Ornamental kale snapdragons and sorbet violas make a dazzling container plant display.

Here are a few suggestions of Louisiana Super Plants for each category for medium-sized containers.

Thriller plants: Suncredible yellow sunflower, Flamethrower coleus series, Fireworks pennisetum, Senorita Rosalita cleome, Intenz Classic celosia, Flutterby Tutti Frutti buddleia, Camelot foxglove series, Diamonds Blue delphinium, Jolt and Amazon dianthus series.

Filler plants: Beacon impatiens series, Babywing begonia series, Serena and Serenita Raspberry angelonia, Mesa gaillardia series, Butterfly and Lucky Star pentas series, Sorbet viola series, compact varieties in the Sunpatiens impatiens series, Kauai torenia series.

Spiller plants: Mini Vista Indigo and Vista Bubblegum in the Supertunia petunia series, Homestead Purple verbena, lemon sedum.

Heather Kirk-Ballard, Ph.D.
Consumer Horticulture Specialist

Checklist for March, April, May


A basket full of purple egg plants with white verigation.
Eggplants.

March

  1. In the vegetable garden: Work compost and a preplant complete fertilizer, such as 13-13-13, at seven to 21 days before planting or laying mulch cloth. In south Louisiana plant beans, cantaloupes, collard greens, sweet corn, eggplants, herbs, mustard greens, okra, Southern peas, peppers, pumpkins, summer squash, tomatoes and watermelons. North Louisiana should wait until the beginning of April.
  2. In the lawn: Make your first mowing at a low setting and remove grass clippings. Continue to treat cool-season annual weeds in the lawn. Let your lawns begin to green up before you start fertilizing lawns this month after March 15 in south Louisiana and after April 1 for north Louisiana.
  3. In the landscape beds: Continue to enjoy your cool-season bedding plants that were planted in fall. They will have another outstanding display of color this early spring before it is time to replace them with warm-season bedding plants around the beginning of May.
  4. Trees and shrubs: Spring is a great time to plant new trees and shrubs. Consider size, fall foliage change, flower interests and whether you want evergreen or deciduous trees or shrubs when selecting new plants. Apply dormant oils to control scales, whiteflies and other sucking insects on trees and shrubs that may be affected. Fertilize this month if you missed it in February. Begin your preventative rose spray program in early March. Alternate fungicides to control blackspot and powdery mildew. Treat in the early morning or late evening every week. Copper is a great organic alternative to other traditional fungicides.
  5. Fruit: Apply fertilizer to fruiting trees that were not fertilized in winter now at the recommended rate. Recommended 8-8-8 fertilizer rates:
    • Blackberry – Half of a pound per plant.
    • Blueberry – Fertilize with 2 ounces per year of growth up to 1 ½ pounds.
    • Fig – 1 pound per year of 8-8-8 up to 10 pounds.
    • Citrus, peaches and plums – 1 to 1 ½ pounds per year of tree age up to a maximum of 8 pounds.
A flowerbed with tall, heat-shaped, white and green veriegated caladiums standing over some short dark green and purplish ornamental plants.
Caladiums.

April

  1. In the vegetable garden: Apply pine straw mulch to prevent weeds in the vegetable garden. The last week of April is a good time to side-dress vegetables planted in late March with ammonium nitrate, ammonium sulfate, calcium nitrate or potassium nitrate. Be sure to apply several inches away from the base of the plant and water in immediately to prevent burning. Stake tomatoes when the first flower clusters to prevent fruit from touching the ground and to help prevent fruit rot.
  2. In the lawn: Fungal diseases are common this time of year. Keep an eye out for large patch and gray leaf spot. St. Augustinegrass is susceptible and centipedegrass is more resistant. Use fungicides containing maneb, myclobutanil, PCNB, propiconazole, thiophanatemethy or triadimefon every 10 days as the fungus persists. Control cool-season annual weeds, such as bedstraw, chickweed and henbit, from producing seeds that will be a headache next winter if not taken care of now
  3. In the landscape beds: You can begin planting warm-season annuals, perennials and caladium bulbs this month. Thin border plants and clumping ground covers, such as monkey grass, liriope and hostas, this month. Use a 2-inch mulch layer on newly planted landscape beds to conserve moisture and to control weeds.
  4. Trees and shrubs: Prune spring-flowering shrubs, such as azaleas, camellias, viburnum and spireas, after they have finished flowering. Fertilize after pruning. Powdery mildew can be a problem on the foliage of ornamentals. Control with fungicides containing one of the following active ingredients: azoxystrobin, copper sulfate, myclobutanil, trifloxystrobin or triforine.
  5. Fruit: Thin fruit on your fruit trees this month. Thinning fruit improves the size and quality of the remaining fruit and can help reduce the spread of diseases.
Several limbs in covered in long dark leaves and bunches of light orange loquat fruits.
Loquats.

May

  1. In the vegetable garden: Now is a critical time to scout vegetable plants for immature stink bugs and leaf-footed bugs. If you see them spray soon. When they turn into adults, they are much more difficult to control. Continue to plant warm-season vegetables.
  2. In the lawn: Be on the lookout for weeds. If weeds are present, you can apply a lawn weed killer labeled for use on your lawn. Early weed control before going into hot summer months is essential for the best turfgrass vigor. If your weeds are under control, you can encourage vigorous turfgrass growth by aerifying your lawn. Plug removal is the best method to provide air to roots. If you fertilized in March, you may go ahead and fertilize again late this month. Lay sod or sprig your lawn this month and throughout the summer, if needed. Trees and shrubs: Mulch trees. Prune ever-blooming roses back by one-third of their height to encourage a vigorous fall bloom.
  3. In the landscape beds: Watering can be laborious in extended droughts in summertime. Consider installing a microirrigation system. Home installation kits and timers are homeowner friendly and readily available online and in stores. Be sure to buy a timer with a rain delay for days with rain. Next month is National Pollinator Month. Plant perennials, such as coreopsis, daylily, Echinacea, gaillardia, gerbera daisy, gaura, milkweeds, Louisiana phlox, passion vine, cardinal flower, sunflowers, bee balm, Mexican sage, verbena, rudbeckia, coral honeysuckle, rose mallow and irises.
  4. Trees and shrubs: This is a good time to prune spring-blooming shrubs now through no later than July to encourage new growth. Be careful not to prune summer-blooming shrubs, such as hydrangeas, butterfly bush and crape myrtles. Azalea lacebugs can be a problem in late spring and into summer. Look for white mottling or spots on the tops of leaves and dark brown insects on the undersides of leaves. Use acephate or malathion to control and be sure to cover the undersides of leaves to control the insects that are found there.
  5. Fruits: Bird netting may be necessary for fruit trees and shrubs this month. It is harvesting time for mayhaws, loquat, mulberry, peach, sweet orange, blackberries and blueberries this month.

Heather Kirk-Ballard, Ph.D.
Consumer Horticulture Specialist

Spring Vegetable Tips


If there is ever a time to be outside in Louisiana, it’s in the short-lived spring season we get. I recommend getting into the vegetable garden as early as possible. January and February are wet and cold. As soon as that garden dries in March, get going before it gets hot. The heat will come in a week, a month or, if we are lucky, in two months … in Louisiana you never know.
Two wood framed, triangular garden beds surrounded by pea gravel and filled with young snap bean and tomato plants.
Snap beans and tomatoes.

Steps to success

  1. Remove weeds and insect- and disease-infested plants from the fall garden.
  2. Work the soil. Loosely till or spade your garden area.
  3. Apply fertilizer or aged manures. A key to achieving heavy vegetable harvests is using adequate fertilizer. For example, most mixed gardens (all warm-season crops combined into one area) require a medium rate of fertilizer. There are hundreds of fertilizers to choose from. To keep the recommendation simple, I would apply one-half pound to 1 pound of 13-13-13 for every 10 linear feet of row in your garden space. That rate is assuming your rows are no wider that 48 inches. That is about 1 to 2 cups of 13-13-13.
  4. Water that fertilizer in!
  5. Plant!!! In south Louisiana plant in early-to-mid-March. In central and northern Louisiana plant April 1 or in late March if we are warm.
  6. Water your newly planted seeds and plants within one hour of planting. Keep the ground moist, not saturated, throughout the life of the garden.
A closeup of a pale yellow okra flower with dark purple center growing on stalk next to an okra pod.
Okra flower and pod.

Vegetables to Plant in March

Direct-plant snap beans, Swiss chard, radish, lettuce, collards, mustards, turnips, cabbage, broccoli and sweet corn seeds. Plant tomatoes, peppers and eggplant transplants. Plant cantaloupes, squash, cucumbers and watermelons well after danger of frost is over. This is usually after March 15 in south Louisiana and closer to April 1 in north Louisiana.

... and in April

Plant snap beans, butter beans, radishes, collards, cucumbers, eggplants, cantaloupes, okra, Southern peas (field peas), peanuts, pumpkins, winter squash, summer squash, sweet corn, sweet potatoes (late April), tomatoes (transplants), peppers (transplants) and watermelons.

... and in May

Most spring vegetables can be planted in May, since the soil has warmed and danger of frost has passed. Plant sweet potatoes (transplants), heat-tolerant tomatoes (Sun Master, Sun leaper, Florida 91, Phoenix, Bella Rosa, for example), okra, Southern peas, pumpkins, peanuts, sweet corn, watermelons, cucumbers, butter beans, squash, cantaloupe, collards and eggplants (transplants). Snap beans, butter beans, sweet corn, tomatoes (except heat-tolerant varieties) and peppers (transplants) should be planted in the early days of May to prevent poor fruit set because of high temperatures.

Enjoy the Garden,

Kathryn “Kiki” Fontenot, Ph.D.
Vegetable Gardening Specialist

Lawn Weed Control


Herbicides can be effective tools for reducing weeds in your yard, but the best way to manage weeds is to grow a thick, healthy lawn. Lawns that are managed properly are lush and healthy, with few weed problems.
A short, wide growing plant called blue eyed grass growing in turfgrass.
Blue eyed grass is an iris that often infests lawns in the early spring.
A plant with three lobed leaves with red fruit growing in turfgrass. There are pine needles scattered over the top of the weed.
Indian mock strawberry infests thin lawns.
Close up of a small plant emerging from the soil. A dime is put next to the seedling to show scale.
Crabgrass emerges in early February in south Lousiana.
A large patch of weeds called spotted burclover growing in turfgrass. Each leaf has three lobes with brown spots on a green leaf.
Spotted burclover is a common weed seen early in the spring.

Pre-emergence herbicides

Weed preventer or pre-emergence herbicides can be helpful in preventing the emergence of several summer annual grasses and broadleaf weeds. Pre-emergence herbicides may be applied safely in late winter to early spring to all established southern lawns. Most pre-emergence products for home lawns are granular and should be applied with drop or broadcast spreaders and “watered in” soon after application. These types of herbicides kill weeds as they germinate, so application timing is extremely important. You must apply before the weeds, such as crabgrass, germinate. Also, these pre-emergence herbicides that you are applying to prevent summer weeds will not kill any existing winter weeds. Residents in the New Orleans area and southernmost areas of the state should apply pre-emergence herbicides in late January or early February and then follow up with another application in mid-April. From Alexandria to Baton Rouge, residents should apply around Feb. 10, with a follow-up application in late April. If you live in north Louisiana, try to get these herbicides applied in late February, with a follow-up application by early May. Some pre-emergence herbicide trade names to look for are Scotts Halts, Barricade and Hi-Yield Crabgrass Preventer with Dimension. Consult product labels concerning rates and application techniques. When it comes to the successful use of pre-emergence herbicides, going a little early with your applications is better than applying too late. Winters over the last few years have been nearly nonexistent. Lack of cold weather has caused an earlier emergence of summer weeds. Let’s get those pre-emergence herbicides out on time.

Post-emergence herbicides

Post-emergence herbicides are used to kill weeds that already have emerged in the lawn. Winter broadleaf weeds usually are prevalent in the late winter to early spring throughout the state. MSM Turf (metsulfuron) and Celsius (theincarbazone-methyl + dicamba + iodosulfuron) are two highly effective broadleaf killing herbicides that have consistently performed well in LSU AgCenter evaluations on winter broadleaves. MSM is effective on wild onion, false garlic and blue-eyed grass (an iris), as well as most winter broadleaves. These are low-use-rate herbicides, especially MSM. Follow the product labels very carefully so that lawns and trees are not injured. Do not use Celsius on carpetgrass. More widely available broadleaf weed killers include “trimec type” herbicides formulated with the active ingredients 2,4-D; dicamba; and mecoprop. Some examples of trade names to look for with these active ingredients include Trimec Southern, Ortho Weed B Gon for Southern Lawns, and Ferti-lome Weed Free Zone. Product manufacturers will often recommend a follow-up spray two or three weeks after the first application. Broadleaf weed killers such as these are widely available and can be used on most southern grasses. Injury can occur, however, when using them on St. Augustinegrass and centipedegrass as the weather gets warmer in late spring. Atrazine is an herbicide that is effective on winter broadleaves and also controls annual bluegrass, especially when applied before the annual bluegrass flowers. Most garden centers have a good supply of atrazine on their shelves. Weed and feed products labeled for St. Augustinegrass and centipedegrass contain atrazine as their active ingredient. However, liquid atrazine sprayed on weeds in the yard has worked better in LSU AgCenter trials than atrazine weed-and-feed products impregnated on a fertilizer granule.

What about weed-and-feed products?

Weed-and-feed herbicides can be used at the times recommended for the first fertilizer application of the year. Apply weed-and-feed in the New Orleans area from mid-to-late March. For north Louisiana, early-to-mid-April is the time. Just be aware that applying weed-and-feed too early (late February to early March) may encourage outbreaks of large patch disease. Clean your sprayers thoroughly with an ammonia solution if the same sprayer is used for applying insecticides or fungicides on landscape plants. It is best to buy a sprayer specifically dedicated for weed killers, however, to avoid accidental injury to desirable plants. As always, be sure to read and follow product label recommendations before using any pesticide.

Fertilizing the lawn

Lawns vary in the amount of fertilizer required during the growing season. See the table below for information regarding the number and timings of fertilizer applications recommended for lawn species grown in Louisiana. Bermudagrass and St. Augustinegrass require the most fertilizer compared to other lawn grasses. Centipedegrass and zoysia only require one to two applications of fertilizer per year.

Lawn

Number of fertilizer applications/year

Recommended months

Bermudagrass

3

March/April, June, August (optional September)

Centipedegrass

1 to 1.5

April and possibly June at ½ fertilizer rate

St. Augustinegrass

2 to 3

April, June, August

Zoysia

2

April and July


Which fertilizer should I use during the growing season?

A spring application of weed and feed could serve as your first fertilizer application. For future applications during the growing season, consider using 3:1:2 or 4:1:2 ratios of nitrogen, phosphorus and potassium (N-P-K) as a guide for the analysis of fertilizers to choose for the lawn. For example, a fertilizer with an analysis of 21-7-14 is a fertilizer with a 3:1:2 ratio. You would be better off getting your soil tested. Soil tests would be most helpful to determine exactly what nutrients are needed to make your lawn beautiful. Contact your parish extension office concerning soil sampling your yard today.

Ron Strahan, Ph.D.
Weed Scientist and Turfgrass Specialist

Exobasidium Leaf Gall


Leaf gall of camellias and azaleas is a fungal disease favored by extended periods of cool, wet weather during spring. This is primarily a leaf disease, but occasionally it may occur on stems, flowers and seed pods. There are mainly two species of the Exobasidium fungus that cause this disease: Exobasidium vaccinii on azaleas and E. camelliae on camellias. Symptoms of leaf galls start appearing soon after the plants finish flowering. Leaves are distorted and become thickened with a fleshy or leatherlike texture (Figures 1 and 2). Galls tend to be pale green, pink or white (Figure 3) in the beginning, but as they develop, they become white and powdery. The white powder material is spores of the fungus, which readily disperse via air currents and by splashing water. As the galls get older, they shrivel up, dry out and turn brown and hard (Figure 4). Older galls fall to the ground, where they survive and may serve as a source of inoculum for the next spring’s susceptible growth.
A camellia branch with three white galls on the end of the branch.
Figure 1: A leaf gall on a camellia. Photo by Raj Singh.
Three groups of camellia leaves showing varying levels of color. Some are green, pink and brown.
Figure 3: Camellia galls show color variations. Photo by Raj Singh.
Two groups of azalea leaves laying flat on a white table. There are several protruding green galls on the leaves.
Figure 2: A leaf gall on an azalea. Photo by Raj Singh.
Close up of light brown distorted foliage.
Figure 4: An older mature gall turns brown on an azalea. Photo by Raj Singh.
Management of leaf galls is achieved primarily by adopting good cultural practices. Proper pruning and discarding of galled leaves is very important in reducing the spread of the disease. Cut galled leaves a couple of inches below the symptoms. Before discarding them, put them in zippered plastic bags. Remove and destroy affected leaves with galls that have fallen on the ground. Improve air circulation by selective thinning of the canopy of established plantings to promote rapid drying of foliage and maintain adequate spacing when establishing new plantings to avoid creating favorable conditions for disease development. Fungicides may help avoid infection when applied beginning at bud break. Repeated applications may be required every 10 days as long as the conducive weather conditions persist for disease development. For fungicide selection, please consult your local LSU AgCenter extension agent. For more information on leaf galls of azalea and camellia, please contact Raj Singh at 225-578-4562 or email rsingh@agcenter.lsu.edu.

Raj Singh, Ph.D.
Associate Professor
Director, Plant Diagnostic Center

4/21/2022 3:14:42 PM
Rate This Article:

Have a question or comment about the information on this page?

Innovate . Educate . Improve Lives

The LSU AgCenter and the LSU College of Agriculture

Top