August Gardening Tips

August gardening tips


Vegetables for August Planting

Broccoli Raab
Mesclun Mixes
Pak Choi

Herbs for August Planting

Bronze Fennel

August is a tough month for gardeners—it’s hot, humid, and dry, not much is in bloom, and insect pests abound. We could sit back and enjoy the fruits of our labor, but there’s still work to be done…

Must Do

  • Continue to mow grass high, using a mulching mower. If you allowed your lawn to go dormant (don’t worry, cool-season grasses will recover in the fall), you’ll need to mow far less often.
  • Water plants as needed, especially containers (which dry out easily) and perennials or shrubs planted earlier this year to help them get established. The garden needs at least 1” of water weekly. Water early in the day and, if possible, use drip irrigation. Infrequent, deep watering is best.
  • Remove vegetables that have finished producing and put them in your compost pile. However, if your plants have had any disease, insect, or nematode problems, toss them in the trash to avoid a recurrence next year.
  • Fluff up mulch so whatever rain we do get can percolate through to the plants’ root zone. Keep a 2”-4” layer of mulch around trees and shrubs, and 2” around annuals and perennials. Be sure to keep the mulch a few inches away from plant trunks or stems.
  • Stop fertilizing roses.

Should Do

  • Pull weeds and monitor for disease and pests at least weekly. Insects like scale, spider mites, leaf miners, and leafhoppers can be a problem. Japanese beetles are a major pest at this time of year. You can spray them, if needed, but removing by hand is more effective. Avoid spraying pesticides on very hot days or when plants are drought stressed.
  • Continue deadheading flowering plants, especially annuals, to keep them in bloom. However, if you have repeat-blooming roses, stop deadheading them now so they can produce rose hips for fall.
  • After Oriental and Asiatic lilies bloom, cut off the top of the stalk taking no more than one third of the stem. The idea is to leave enough foliage so the plant can build up energy in the bulb for next year’s blooms.
  • Continue harvesting vegetables from the garden. Some varieties such as okra, snap beans, squash and cucumbers will stop producing if fruits are allowed to over ripen on the plant.
  • If ants have invaded your potted plants, place the container in a saucer filled with water. The ants will move on to drier ground.
  • If grubs have been a problem, apply grub control. A small number of grubs are beneficial, but if you have more than 10 per square foot or have a problem with foraging animals tearing up you lawn, now is the time to take action. Read more about grub control here.
  • Stake tall-growing flowers to prevent them from falling.
  • Prune ‘bleeder’ trees like maple, dogwood, birch and elm, as well as the fruiting canes of raspberry and blackberry plants after harvest is over. Cut canes at ground level. Do not prune spring-flowering shrubs now or you won’t have any blooms next year.
  • Add compost as a top dressing around your shrubs and perennials. It will help hold moisture and will enhance the soil to help promote the long-term health of your plants.
  • Cut down foliage on plants that are going dormant (such as poppies and bleeding heart), need rejuvenating (like  petunias, or bee balm, which often has powdery mildew by now and will benefit from a hard ‘hair cut’), or have become too tall or top heavy (such as impatiens, begonias,and salvia)

Nice to Do

  • Apply your last dose of fertilizer to most plants so that new growth has time to harden off before the colder weather returns. Don’t fertilize shrubs in August, September, October or November, it could cause new growth at a dangerous weather time.
  • In late August, prepare the lawn for seeding tall fescue or bluegrass. Seed or fertilize lawns the last week of August.
  • Remove flower stalks from daylilies and hostas to keep them looking tidy.
  • Repot and root prune house plants and container plants to give them more room for roots to grow and fresh potting soil.
  • Fall is now considered a third growing season. Check garden centers for new arrivals that are suited for the cooler temperatures and shorter days of autumn.
  • Sow seeds of short season vegetables which tolerate cooler nights and shorter days and provide tasty fall harvests (see list at left for herbs and vegetables that can be planted now).
  • Sow seeds for hollyhock, delphinium and stokesia so that they will be ready to bloom next year.

Note: The August gardening tasks described here are for gardeners in zone 6. Tasks may be done earlier, or later, if you live in warmer or colder areas.