April Horticulture Hints

April is a busy month for gardeners in the South. Much work must be done if gardens are to look their best this season. Gardeners don’t mind, however, for doing the work is one of the pleasures of gardening.

Lawns

As soon as the lawn is completely green, it can be fertilized with a fertilizer with a high first number (nitrogen), a low middle number (Phosphorus) and a last number (Potassium) that is about half as large as the first number such as 16-4-8, 12-4-8, or 26-0-13. About half the nitrogen should be in slow release form, and one pound one pound of actual nitrogen should be applied per thousand square feet of lawn.  

Centipedegrass, bahiagrass, and carpetgrass are low fertility grasses. They will grow best and have fewer problems when fertilized only once (twice at the most!) a year. St. Augustine usually does best with a spring and summer application.

Maintain St. Augustine lawns at 2.5 to 4 inches tall and centipedegrass at about 1.5 to 2.0 inches. Mow frequently so that no more than one-third of the grass blade is removed per mowing.

Water only as need is evidenced by folding of leaf blades, graying of color, or when footprints remain for an extended period of time. Then water deeply, applying at least ½ inch of water as measured in rain gauges.

Consider replacing grass in areas where it does not do well with an adaptable groundcover. Mulch is an alternative if no plants are wanted. Groundcovers for the South is a resource if you need information about groundcovers.

Perennials and Annuals

April is one of the best times to plant tender annuals. Frost is surely a thing of the past, and many are available at garden centers. Though it is not too late to plant seeds, most of these plants can be purchased ready for transplanting into the landscape.

Before planting annuals, add compost, peat moss, or other organic matter to the soil. Dig or till in thoroughly. Sprinkle the ground with slow-release fertilizer, and spread organic mulch such as bark chips or pine needles over the entire bed. Water thoroughly. When you are ready to plant your annuals, rake aside the mulch and plant so that the top of the soil around your plant is level with the soil in the prepared bed. Do not allow mulch to touch the stems of newly planted annuals. Water again after planting, and every day or so until plants are established. Gradually decrease the frequency of watering until the plants are able to make it on a once-a-week deep watering (about ½ inch).

Plant seeds of annual vines such as moonflower, hyacinth bean vine, Malabar spinach, cypress vine, cardinal vine, morning glory, and love-in-a-puff. Soak seeds overnight or until they have swollen and absorbed water. Germination will be quick, and they may be planted in containers or directly in the ground.

Plant bulbs such as achimines, walking iris, gingers, agapanthus, crinums, gladiolus, lilies, society garlic, canna, dahlia, gloriosa lily, and lycoris. Enjoy amaryllis and iris as they bloom this month. Fertilize spring bulbs with a bulb fertilizer such as 5-10-10.

Plant daylilies, lantana, verbena, salvias, sedum, purple coneflower, rudbeckia, and summer phlox. Include some ornamental grasses, gingers, and in shady places try aspidistra or ferns. Divide and transplant fall-blooming perennials such as aster and chrysanthemum.

Protect tender plants with snail and slug bait. Check plants for spider mites, aphids, and caterpillars, and treat, if necessary, with an insecticide labeled for control of these pests.

Container Plants

Start hanging baskets and containers this month. Choose a spiller or trailing plant to tumble over the sides of the container, a filler to flesh it out, and a tall, stunning plant (the thriller) for a combination that is sure to please. Try a container for butterflies and hummingbirds, or plant an assortment of herbs to enjoy all summer.

Plants in pots are portable, and you can move them where they are needed when they look their best. Place a few around your patio, at the edges of the pool, at the front entrance, or in a dull spot in the landscape.

Move houseplants outside for the summer, if desired. Most will benefit from a vacation out of doors. When you move them, evaluate their needs for this growing season. Do they need repotting? Are insects present? Do they look terrible and need to be thrown away?

Crowded houseplants will need to be repotted. If you wish the plant to stay the same size, prune the top and the roots and replace it in the same container. Fill in around the roots carefully with fresh soil. If you wish the plant to grow bigger, move it up to a pot about 2 to 3 inches larger than the one it was in.

If insects are present, do whatever is needed to control them. Spider mites, scale insects, and mealy bugs can proliferate indoors. Most can be controlled with a spray of insecticidal soap or horticultural oil.  

After evaluating and taking corrective measures, be sure to select a site suitable for the plants. Most will appreciate a place in shade. At any rate, never place a plant that has been indoors all winter in direct sunlight. The leaves will burn and it will take them a long time to recover. If the plant is tolerant of sun, acclimate it gradually to increasing light. Water the plants on a regular basis, and give them a bit of slow-release fertilizer for a perfectly thrilling summer vacation.

Trees and Shrubs

Continue to prune spring-blooming shrubs as they finish blooming. This year’s growth makes excellent material for cuttings if new plants are wanted. Take four- to six-inch cuttings and place them in damp soil or potting medium. You might also try layering a low branch. Nick or wound the branch you want to root and then cover it with soil. Pin it or weight it down with a brick to keep in close contact with the soil. Cuttings started in this manner should be ready to remove from the mother plant by fall.

Organic 6-6-6 or other balanced fertilizer is a good choice for most trees and shrubs. However, use an acid fertilizer on azaleas, camellias, blueberries, and other shrubs that prefer acid soil. Select fertilizers formulated for citrus and palm if these are in your landscape. Apply according to package directions.

Prune the lower limbs of trees if they interfere with foot traffic or yard maintenance. Check your trees and remove any dead or weak limbs that may fall during high winds. Consider thinning the canopy of trees to make them more tolerant of high winds.

Divide and transplant overcrowded perennial herbs and flowers. Fertilize perennial beds with organic 6-6-6 or a long-lasting, slow-release fertilizer formulated for the garden.

Vegetables

When the cotton farmers start planting cotton, it is time to plant warm-weather vegetables. Seeds to plant: green beans, okra, squash, corn, carrots, lettuce, butterbeans, cucumbers, and melons.

Transplant tomatoes, peppers, onions and other vegetables. Stake tomatoes when you plant them or soon after with a rigid stake that is at least five feet tall. Secure plants to stakes as they grow.

If you do not have a large garden area, try a few vegetables and herbs in containers. Patio tomatoes and pepper plants are particularly rewarding.