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Monthly Horticulture Tips

April Gardening Tips

Oklahoma Cooperative Extension Service, Division of Agricultural Sciences and Natural Resources

Department of Horticulture & Landscape Architecture, Oklahoma State University

David Hillock, Consumer Horticulturist

Download the full list of April Gardening tips

Trees & Shrubs

  • Proper watering of newly planted trees and shrubs often means the difference between success and replacement.
  • Remove any winter-damaged branches or plants that have not begun to grow. Prune spring flowering plants as soon as they are finished blooming. (HLA-6404, HLA-6409)
  • Control of powdery mildew disease can be done with early detection and regular treatment. Many new plant cultivars are resistant. (EPP-7617)
  • Fungicides for leaf spot diseases of ornamentals can be applied.
  • Diplodia tip blight fungicide applications should be applied at bud break.

Flowers 

  • Most bedding plants, summer flowering bulbs, and annual flower seeds can be planted after danger of frost. This happens around mid-April in most of Oklahoma. Hold off mulching these crops until spring rains subside and soil temperatures warm up. Warm-season annuals should not be planted until soil temperatures are in the low to mid 60s.
  • Harden off transplants outside in partial protection from sun and wind prior to planting.
  • Let spring flowering bulb foliage (daffodil, tulip, etc.) remain as long as possible before removing it.

Lawn

  • Warm-season grass lawns, such as Bermudagrass, zoysiagrass or, in southern Oklahoma, St. Augustinegrass, can be established beginning in mid-April from sprigs, plugs or sod. (HLA-6419)
  • Mowing of warm-season lawns can begin now (HLA-6420). Cutting height for bermuda and zoysia should be 1 to 1½ inches high, and buffalograss 1½ to 3 inches high.
  • Damage from Spring Dead Spot Disease (SDS) becomes visible in bermudagrass (EPP-7665). Perform practices that promote grass recovery. Do not spray fungicides at this time for SDS control.
  • Grub damage can be visible in lawns at this time. Check for the presence of grubs before ever applying any insecticide treatments. Apply appropriate soil insecticide if white grubs are a problem (EPP-7306). Water product into soil.
Download the full list of April Gardening tips

Landscape – General

  • Hummingbirds arrive in Oklahoma in early April. Get your feeders ready using 1-part sugar to 4-parts water. Do not use red food coloring.
  • Keep the bird feeder filled during the summer and help control insects at the same time.
  • Lace bugs, aphids, spider mites, bagworms, etc. can start popping up in the landscape and garden later this month. Keep a close eye on all plants and use mechanical, cultural, and biological control options first.
  • Be alert for both insect pests and predators. Some pests can be handpicked without using a pesticide. Do not spray if predators such as lady beetles are present. Spray only when there are too few predators to be effective.
  • Clean out the water garden and prepare for season. Divide and repot water garden plants.
  • Begin feeding fish when water temperatures are over 50°F.
  • Nutsedge plants can become visible during this month but wait until May for treatment.

Fruit 

  • Don’t spray insecticides during fruit tree bloom or pollination may be affected. Disease sprays can continue according to schedule and label directions. (EPP-7319)
  • Control cedar-apple rust. When the orange jelly galls are visible on juniper (cedar), following a rain, begin treating apple and crabapple trees with a fungicide. Treat hawthorns accordingly. (EPP-7319, EPP-7611)
  • Fire blight bacterial disease can be controlled at this time. Plant disease-resistant varieties to avoid diseases.
  • Continue spray schedules for disease prone fruit and pine trees.

Vegetables

  • Wait a little longer for it to warm up before planting cucurbit crops and okra.
  • Plant vegetable crops in successive plantings to ensure a steady supply of produce rather than harvesting all at once.
  • Cover cucurbit crops with a floating row cover to keep out insect pests. Remove during bloom time.
  • Watch for cutworm damage and add flea beetle scouting to your list of activities in the vegetable garden.

Pruning Hydrangeas

By David Hatlock, OSU, Senior Extension Specialist

Hydrangeas are one of the more popular plants in the landscape. They have attractive foliage and typically produce large, striking flowers. Hydrangeas are generally easy to grow and tolerate a wide variety of soil. About the only care they need is pruning, however, there are different types of hydrangeas that require different pruning techniques depending on the time of flowering.

Hydrangeas that bloom in the spring, usually before May and June, bloom on last year’s growth. Those that bloom later flower from buds formed on the new wood that growing season. Varieties that bloom in spring should be pruned after they flower while those that bloom on new wood can be pruned, if necessary, in late winter, early spring before new growth develops.

So, which are which? The types that bloom on old wood include the mophead, big leaf, and lacecap types, which are Hydrangea macrophylla varieties, and the oakleaf hydrangea, H. quercifolia. These all produce flower buds on last year’s wood.

Types that bloom on new wood include the panicle hydrangea, often referred to as PeeGee types, Hydrangea paniculata, and the smooth hydrangea, often referred to as the Annabelle types, H. arborescence.

The one exception is the variety ‘Endless Summer’, which blooms on old and new wood. In all cases it is helpful to remove old blossoms as they fade.

If you’re not sure of which type you have, the safest approach is “no pruning is better than the wrong type of pruning.” However, you can also take a simplified approach which is suitable for all types. The simplified approach includes removing only winter-killed wood or all dead stems in the spring before or as the buds are opening. You can check for live wood by scratching the stems with your thumbnail or a knife, if it is green, it is still alive, brown, and hard it is dead and should be removed. 

Rejuvenation is another way to keep your plants healthy by removing dead or very old stems by cutting them back to the ground, this will stimulate new growth and produce more blooms later.

Today there are a wide variety of hydrangeas; make sure you choose a variety that will suit your landscape needs, as well as the site. Most like some water and most prefer a little protection from the hot Oklahoma afternoon sun. With good choices, and correct timing with pruning, your hydrangeas will be the envy of the neighborhood.

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