May: Gardening To-Do List


  • Use Marcum’s Redbud Compost with root stimulator for best results. It’s gold for your garden!
  • Set out annual bedding plants for summer color.
  • Soak new transplants and newly planted tress unless rainfall is abundant. See Marcum’s watering guidelines for details.
  • In mid-May, treat for pine needle diseases with copper fungicide.
  • Clean needles away from under trees.


  • Seed warm-season grasses (Bermuda and Zoysia) in mid-May through the end of June.
  • Fertilize cool-season lawns with Marcum’s Original Slow Release Fertilizer (18-6-12) if you did NOT fertilize in March or April.
  • Fertilize warm-season lawns with B.R.’s Lawn Tonic (28-6-12) or Big Mont’s Nitro Green (31-0-0).
  • By mid-May, “Dollar Spot” disease may be visible on lawns. Apply ferti-lome Liquid Systemic Fungicide or ferti-lome F-Stop. Be sure to fertilize prior to applying a fungicide.
  • As nut sedge plants become visible, apply post-emergent treatments (Sedgehammer) once warm-season grasses are completely green.
  • Apply the second application of pre-emergent, Hi-Yield Ornamental Weed Preventer with Dimension or orzulyn herbicide mid-May or early June depending upon timing of first application. Check label for details.
  • Plant your container Ball & Burlap (B & B) trees.
  • Plant your shrubs and perennials.
  • Apply Hi-Yield’s Grub Free Zone II to control mole crickets.
  • Apply Thuricide or Hy-Yield Malathion for the following:
    • Bagworms on juniper and arborvitae (late May)
    • Leaf beetles and larvae on elms and zelkova (late May)
    • Webworms on mimosa and honeylocust
  • Apply Hi-Yield 38 Plus or Hi-Yield Malathion for lace bugs on sycamore, pyracantha, and azaleas.
  • Average rainfall of Oklahoma in May is 6.28 inches.
  • Mulch with Marcum’s twice ground cedar mulch to aid your plaints in moisture control as summer is quickly approaching. 

Note: Thanks to Oklahoma Coop Extension Service for providing some of the suggested maintenance guidelines.

For questions regarding May maintenance guidelines, please call Goldsby 405 288-2368, Oklahoma City 405 691-9100,  Norman 405 447-3100 or Ardmore 580 223-1846.