Extension

Trees and Shrubs

• Prune and feed azaleas immediately after blooming.
• Insect Alert: (Ornamental and Lawn Pest Control EPP-7306)
  • Mimosa webworms on mimosa and honey locust.
  • Lace bugs on sycamore, pyracantha, and azalea.
  • Bagworms on juniper and arborviate.
  • Elm leaf beetles and larvae on elms.
• Soak new transplants and newly planted trees unless rainfall is abundant.
• Pine needle disease treatments are needed in mid-May.

Flower Beds

• Annual bedding plants can be set out for summer color.
• Plant summer bulbs such as cannas, dahlias, elephant ear, caladiums, and gladiolus.
• Shake a leaf over white paper to look for spider mites. If the tiny specks begin to crawl, mites are present.

Vegetables

• Plant warm season crops like watermelon, cantaloupe, cucumber, eggplant, peppers, okra, and sweet potatoes.
• Continue maintaining cool season vegetables until they are ready for harvest. Increase irrigation during warm spells.
• Avoid planting vegetable plants too closely together. Crowding leads to a more humid microclimate, thus increasing chance for diseases.
• Scout diligently for common vegetable pests. It is much easier to control a small population than it is a large population of insects.

Lawn and 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 in May. (Lawn Management in Oklahoma HLA-6420)
• The 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 fertilize applications have been adequate before ever applying a fungicide. (Dollar Spot of Turfgrass EPP-7658)
• Nutsedge plants become visible during this month. Post-emergent treatments are best applied for the first time this month (Controlling Weeds in Home Lawns HLA-6421). Make certain warm-season grasses have completed green-up.
• The second application of pre-emergent annual grass herbicides can be applied in late-May or early June, depending upon timing of first application (Controlling Weeds in Home Lawns HLA-6421). Check label for directions.
• Vegetative establishment of warm-season grasses can continue. (Establishing a Lawn in Oklahoma HLA-6419)

Fruit and Nuts

• Fruit spray programs should be diligently continued throughout May and early June.
• Late May is the best time to control borders in the orchard. Always check for label recommendations.

General

• Keep the bird feeder filled during the summer and help control insects at the same time.
• Schedule a group tour of the OKG Studio Gardens in Stillwater between the first of May and late October!
• 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.