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Oklahoma City, OK 73102

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Reopens fall 2022.

Monthly Horticulture Tips

May 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


  • Annual bedding plants can be set out for summer color.
  • Plant summer bulbs such as cannas, dahlias, elephant ear, caladiums, and gladiolus.

Water Gardens

  • Clean out water garden and prepare for season. Divide and repot water garden plants.
  • Begin feeding fish when water temperatures are over 50°F.

Fruits & Nuts

  • Plant watermelon, cantaloupe, cucumber, eggplant, okra, sweet potatoes, etc.
  • Fruit spray programs should be faithfully continued during the next several weeks. (HLA‑7319).
  • Late May is the best time to control borers in the orchard. Check for label recommendations and controls.

Tree & Shrub

  • Prune and feed azaleas immediately after blooming.
  • Insect Alert: (EPP-7306)
  • Bagworms on juniper and arborvitae. (Late May)
  • Elm leaf beetles and larvae on elms. (Late May)
  • Mimosa webworms on mimosa and honeylocust.
  • Lace bugs on sycamore, pyracantha, and azalea.
  • Soak new transplants and newly planted trees unless rainfall is abundant.
  • Pine needle disease treatments are needed in mid-May.
Lawn & Turf
  • Cool-season lawns can be fertilized again. If you did not fertilize cool-season grasses in March and April, do so now.
  • Warm-season lawns may be fertilized again in May. (HLA-6420)
  • Seeding of warm-season grasses such as bermudagrass, buffalograss, zoysiagrass and centipedegrass is best performed in mid-May through the end of June. The soil temperatures are warm enough for germination and adequate growing season is present to promote winter hardiness.
  • Dollar spot disease of lawns can first become visible in mid-May. Make certain fertilizer applications have been adequate before ever applying a fungicide. (EPP-7658)
  • Nutsedge plants become visible during this month. Post-emergent treatments are best applied for the first time this month. Make certain warm-season grasses have completed green-up. (HLA-6421)
  • The second application of pre-emergent annual grass herbicides can be applied in late-May or early June, depending upon timing of first application. Check label for details. (HLA‑6421).
  • Vegetative establishment of warm-season grasses can continue. (HLA-6419)

Water Saving Tips

Plants need water, but how you water and how much you water can make a big difference in plant health and how much your pocketbook is affected. Below are some tips on how to water so you don’t waste water or money and have healthy plants.

  • Water deeply, but infrequently. Allowing the water to soak into the ground and letting the soil dry out between watering forces plants to produce strong, deep roots.
  • Mulching retains soil moisture, prevents erosion, controls weeds, and increases soil quality.
  • Install a rain sensor. A rain sensor turns the irrigation system off during and immediately after a rain event.
  • Don’t water hardscapes. Make sure sprinklers are watering the lawn and not the street or sidewalks.
  • Avoid heavy pruning. Pruning stimulates growth and your plants will require more water.
  • Mature plants require less water. Mature plants and trees have deep root systems and can be watered less frequently.
For more tips on water saving we recommend visiting squeezeeverydrop.com

Growing in Raised Beds

Raised bed gardens are an ideal way to grow vegetables and small fruit. They are elevated a few inches or more above the soil level, and just wide enough to reach across by hand. Plants can be grouped together in a bed with permanent walkways on either side. The soil does not get compacted since the soil in which plants are grown is never walked on.

 The idea of growing plants in single file or “row crops,” started with the use of a horse and plow to cultivate crops on a large scale. The straight rows, far enough apart to drive a horse between, made plowing easier. Wider spaces later accommodated tractors and their implements. Not knowing the reasons behind growing crops in rows, many home gardeners plant single row vegetable gardens. However, foot traffic on each side of a single row can severely compact soil by the end of a growing season. The excessive row spacing also wastes garden space that can be planted with crops.

Raised bed gardens can range from a simple rectangular plateau of soil to a more elaborate bed framed in wood, stone and mortar, straw bales or modern snap-together plastic blocks. Although more expensive and time consuming to build, permanent structures will keep soil in place during heavy rains and will look nicer in the landscape. However, for a large garden, several beds of mounded soil are very adequate to achieve desired results. Just make sure plenty of mulch is used on the soil to hold it in place during drenching rains.

Benefits of Raised Beds

Higher Yields. Raised beds allow more garden space for growing plants, with less space utilized for walking paths. Individual plant yields may be slightly less with less space per plant than in traditional rows, but more plants can be grown in each space.

Better Soil. Amendments such as compost and fertilizer are only spread on beds and not wasted on pathways. Looser (non-compacted) soil also drains better. Frequent tillage of the garden can be elimination.

Water Conservation. Plants grown close together shade the soil, decrease evaporation, and keep roots cooler. Water is only provided to the beds and not the pathways.

Fewer Weeds. Closely planted crops keep weeds crowded out. Pathways can be covered in landscape fabric or mulch to choke out weeds.

Extended Season. Soil in raised beds can be worked earlier in the season, because it warms up faster than soil in traditional in-ground gardens. Rainy weather is less of a hindrance to working in the garden since mud is not an issue.

Better Pest Control. Raised bed gardens are easy to cover with insect screening fabric. Crops are easy to rotate from bed to bed — preventing a buildup of pests.

For more information about using raised beds see our fact sheet HLA-6033 – Raised Bed Gardening.

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