August in the Garden

August begins right in the middle of the “dog days of summer,” the hottest and most sultry time of the year. Ancient cultures believed that the excessive heat was caused by the alignment of Sirius, the Dog Star, with the sun during the summer. These are the days when everything seems languid and still – except mosquitoes, of course – and the sun threatens to bake lawns, gardens, and gardeners alike.

There is plenty to do in the garden in August, although it is best done in the early morning or late evening when temperatures are more comfortable. Whether you’re in cooler climates making early preparations for autumn, or warmer ones enjoying the height of the garden's bounty, here are some suggestions for tasks around your yard and garden in August.

Lawn Maintenance and Preparation

  • Prepare for fall grass seed planting by leveling low spots, removing weeds, and choosing your seed if it needs to be ordered in advance.

  • Aerate your lawn and dethatch it.

  • If there is plenty of rainfall, fertilize your lawn.

  • To help your grass beat the heat and reduce lawn maintenance, keep your lawn mower blade on the highest setting. Don't worry if parts of your yard turn brown this time of year – it happens.

Annuals and Perennials

  • Spring and summer-flowering perennials can be divided and transplanted after blooming. In zones 5 and warmer: divide overgrown plants and discard the extra, or transplant during the coolest part of the day and preferably in the shade.

  • Trim and fertilize your containers – they still have time for another show.

  • Deal with late-season pests – such as aphids, whiteflies, and spider mites – with a spray of water from the hose.

  • Treat diseased plants, and remove diseased foliage before leaves drop.

  • Prune back vigorous climbers such as wisteria, and train them around trellises while the growth is soft.

  • Propagate plants by collecting seeds, taking cuttings, or layering.

  • Continue deadheading! For prolific bloomers like coreopsis and catmint, shear them lightly to encourage more blooms.

  • Label your plants with garden stakes, particularly perennials that die down to the ground in the fall.

  • In colder zones 1-3, begin moving your houseplants indoors to acclimate them.

Vegetables and Herbs

  • Cut herbs to dry or freeze for winter use.

  • Fall vegetable and herb seeds or starters can be planted now. If you live in colder climates, use a cold frame, otherwise sow directly in the ground. Consider spinach, radishes, carrots, beets, lettuce, overwintering onions, kale, kohlrabi, rutabagas, turnips, dill, cilantro, parsley, and chives.

  • Harvest garlic when about half the leaves turn brown.

  • Enjoy your harvest!

Shrubs and Trees

  • Pick up and destroy fallen fruit from fruit trees to limit insect infestations.

  • Make sure newly planted shrubs and trees get plenty of water.

  • Install stakes for training and shaping.

Plan Ahead

  • Place orders for spring bulbs. If you live in a warm climate, put them in the refrigerator to chill.

  • Place orders for shrubs and trees to plant in the fall.

  • Apply compost starter to new compost to speed up decomposition for fall use.

  • Take pictures, or make notes, of plants you like while they're blooming and full of leaves.

  • Take note of the growth habits of shrubs for future pruning – they should be at their fullest about now.


  • Water, water, water! Early morning is the best time to water – target plants directly, and water deeply. Avoid getting leaves wet in the hot sun, and avoid soaking containers during the hottest part of the day – both of these can burn plants.

  • Keep close watch on your birdbath, water features, and hummingbird feeder – take steps to correct or avoid mold, stagnation, and mosquito larvae.

  • Continue weeding, to reduce competition for water and nutrients.

  • Beware of powdery mildew, which is caused by moisture and humidity. Help prevent mildew by watering in the cool of the morning, when roots can absorb water but excess will evaporate as the day warms. Also avoid overhead sprinkling in mildew-prone areas. Do not compost leaves that are mildewed.

  • When the temperature is over 85 degrees, avoid chemical applications such as fertilizer, fungicide, or insecticide.

  • Add compost and mulch to keep your garden cool and to prepare for fall planting.


An August Lawn and Garden To-Do List