Garden Checklist: May


Warm Season Grasses  

Bermuda and Zoysia 

Keep the mower deck at a height of 1-2 inches depending on lawn condition. The optimal soil pH for Bermuda and Zoysia is 6 – 6.5. Add sulfur if the pH is too high or lime if the pH is too low. At this point, the grass should be fully green so apply ½ pound to 1 pound of nitrogen per 1000 square feet every 4-6 weeks. If summer annual weeds like white clover, spurge, and lespedeza become a problem, apply postemergence herbicides. However, do not apply preemergent if the plan is to overseed with ryegrass in Oct/Nov. Continue to water an inch a week unless it is raining. 

Mow frequently enough so that no more than 1/3 of the grass blade is cut. 

Cool Season Grasses  

Kentucky Bluegrass 

Apply a 15-5-10 weed and feed fertilizer to reduce broadleaf weeds while providing the correct balance of nutrients. Use 1 pound of nitrogen per 1000 square feet. Water lawns in the morning with 1 inch of water per week (unless raining) to prevent disease. 

Mow frequently enough so that no more than 1/3 of the grass blade is cut. 

Tall Fescue  

Since this is a cold season grass, set the mower deck height to cut the grass at a height of 3 inches to prevent the grass from wilting/burning up. If mowed frequently, there is no need to remove grass clippings. No fertilization is needed in this time period. Water lawns in the morning with 1 inch of water per week (unless raining) to prevent disease. Apply pre-emergent herbicides as necessary to control weeds. 

Mow frequently enough so that no more than 1/3 of the grass blade is cut. 


  • By the end of the month, it is safe to plant all summer annuals outdoors, including summer vegetables. 


  • Summer bulbs started in containers may still be planted.  
  • Remove brown foliage from spring flowering bulbs as long as they can be pulled off by hand.   

Shrubs and Trees 

  • Fertilize roses monthly according to a soil test.  
  • Prune climbing roses after the first big flush of flowering. 
  • Monitor new landscape plantings of shrubs, trees, and turf. To establish healthy root systems, prevent them from drying out and water deeply. 

Fruits and vegetables 

  • Begin hardening off frost tender plants now including vegetables, herbs, perennials, and annual flowers that have been started indoors. 
  • If the forecast looks good, direct sow seeds outdoors of beans, okra, sweet corn, and watermelon. Plant only partial rows of beans and sweet corn so that successive plantings can be done every week or two. Sweet corn should be planted in paired rows or blocks for good pollination. 
  • Direct sow sunflowers, nasturtiums, marigolds, borage, basil, and other warm season flowers and herbs. 
  • Keep “hilling up” potatoes.  
  • Be sure to harvest leafy greens often because they will soon bolt (go to seed and turn bitter or woody). 
  • Have a trellis system in place for your tomato patch before the plants begin to sprawl.  
  • Keep a close eye on the quality of your spring crops. Hot weather causes lettuce to bolt and become bitter. Plant a warm season crop as soon as the spring vegetables are harvested. 


  • Houseplants can be moved to a shady spot in the yard for their summer vacations if desired. 
  • Keep an eye out for beetles on your summer vegetable crops. If spotted, first try hand removal. If that does not work, identify the insect correctly and then treat appropriately. Always read the label instructions thoroughly before treating.   
  • Aphids of all types show up on a range of host plants as soon as the warm weather arrives. Look for them in newly unfurling foliage and sticky leaves are also a sign of their presence since they secrete a ‘honeydew’. Black sooty mold may also in this sticky substance and while alarming looking does little to no damage since it does not penetrate the leaves. Aphids, however, do damage the plant. Spray leaves with a strong jet of water to dislodge most of them. Insecticidal soap is an organic approved product that should provide satisfactory and retreatment is applied according to the label.   
  • Mulch all landscape beds if not already done. 

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