July Gardening Tips, Tasks, & Problems

Trees & Shrubs

  • Powdery mildew is unsightly on lilacs but rarely harmful. Shrubs grown in full sun are less prone to this disease.
  • Remove infected leaves from roses and clean up any infected leaves that have fallen. If needed, continue spraying roses with a preventative fungicide for black spot
  • Prune climbing roses and rambler roses after blooming if the plants are two years or older.
  • Newly planted trees and shrubs should continue to be watered thoroughly. 
  • Japanese beetles are usually active at the beginning of the month and then taper off. 
  • Lace bugs may still be feeding on azaleas, however, control methods have little effect at this time of year. Take note of infested plants to plan a treatment in the following year. 
  • Holly leaf miner larvae may be feeding this month, however, insecticides may not be effective at this time.
  • Apply final treatment for borers on hardwood trees.
  • Do not fertilize trees & shrubs after July 4th. Fertilizing late may cause lush growth that is susceptible to winter kill. 
  • Fall webworms begin nest building near the ends of branches of infested trees this month. Pruning is not required but can help control, as well as using a BT spray if defoliation becomes severe. 
  • Semi-hardwood cuttings of spring flowering shrubs can be made now.
  • Summer pruning of shade trees can be done now.

Annuals & Perennials

  • Some plants are susceptible to powdery mildew (phlox & peonies), spray with preventative fungicides before a rain.
  • To keep container-planted annuals in bloom and vibrant, fertilize regularly in accordance to the label instructions. 
  • By early to mid-July, iris borer larvae have started to bore into the rhizomes where they will grow then exit in late July - early August to pupate in the soil. 
  • Keep deadheading spent flowers for continued bloom. Cut back to where the flower stem meets the rest of the plant to keep a tidy appearance.
  • Plant zinnia seeds by July 4th for a late bloom in the fall. 
  • Crown rot of perennials is prominent when temperatures are 85-95oF for several days with intermittent rains. Be sure to use sterile practices when removing the plant and excavating the soil. 
  • Bearded irises can be divided now if needed (most should be divided every 3-5 years). 
  • Don't pinch back mums after mid-July or you may delay flowering.
  • The second generation of phlox bugs may be present at this time. Prune off badly infested foliage and dispose. 


  • Water frequently enough to prevent wilting. Early morning irrigation allows the turf to dry before nightfall, reducing the chance of disease.
  • Monitor lawns for newly hatched white grubs. If significant damage is occurring (or if you find more than 1o grubs per square foot of turf), apply appropriate control.

Fruits & Vegetables

  • Blossom-end rot of tomatoes, peppers, and cucurbits occurs when soil moisture is inconsistent. Ensure even soil moisture, applying a 2-3 inch layer of mulch will help.
  • Dig up potatoes when the foliage dies down. Plant fall potatoes by mid-July. 
  • Broccoli, cabbage, and carrot seeds can be directly sown starting in mid-July. Keep well-watered in times of heat, and give shade on the hottest of days. 
  • Sweet corn is ripe when the silks turn brown
  • Cucurbits, tomatoes, and peppers may have pollination issues during this month. Tomatoes and peppers cannot set fruit when temperatures exceed 90oF. During high humidity, cucurbit pollen becomes sticky and does not transfer well. 
  • Be sure to keep cucumbers well-watered as drought conditions can cause bitter fruit. 
  • Harvest onions and garlic when the lower third of the foliage has turned yellow/brown. Let onions and garlic cure for at least two weeks before consuming. 
  • Squash vine borer adults may still be emerging this month. Damage may also start showing up this month. 
  • Cover grape clusters loosely with netting to provide some protection from animals and birds.
  • Prune out and destroy old fruiting canes of raspberries after harvesting. Leave canes that did not fruit that year as they will fruit the following year.
  • Blackberries and thornless blackberries are ripening now. 
  • Early peach varieties are ripening now.


  • To keep weeds at bay, be sure to keep plants from making seeds. Manually remove or use an appropriate herbicide.
  • Hot and dry weather is ideal for spider mite development. Damage appears as stippling on the leaves, yellowing leaves, and thin webbing. 
  • Cicadas start appearing this month.
  • Monitor plants for leafhoppers. Control is rarely needed and is usually difficult as the insects are highly mobile. Sticky traps and insecticidal soap may be effective as needed.
  • Galls may be noticeable on various plants such as oaks, hackberry, and witch hazel. Galls are a normal part of plants and usually do not harm plants. Eriophyid mites are commonly responsible for these galls and do not require any control.