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Download a printable copy of our AUGUST Gardening “To-Do” Checklist.


From the experts at Behnkes and the University of Maryland, here’s what to do this month and how to do it!  If you have questions, comments, additions you’d like to offer for this local resource, leave a comment on this post.

Trees and Shrubs

  • Water deeply, but not frequently. Shrub and tree expert Miri says: “For established plants, don’t water for brief periods every day or every other day – doing so can encourage fungal growth on the constantly wet surface and yet keep deeper roots dry, since the water doesn’t soak in very much and some of it evaporates.  Plus, watering that often wastes water.
    “Here’s the best way to water:  Soak thoroughly.  Soaker hoses and drip systems are best, sprinklers are second-best and hand-held hoses will do if you must.  Just make sure the root area is well soaked and that the water seeps into the soil at least 4-6 inches deep.  A guideline is to put down at least an inch of water, so if you use a sprinkler, measure how long it takes to fill a shallow can or dish about one inch deep. You’ll have to experiment a bit, but probing the soil down to about five inches gives you a better idea of how moist the roots are getting.”
  • Miri also reminds everyone to get the last of our needed pruning done now, or wait until early winter to resume shaping shrubs or trees. Fall pruning can lead to a last-minute flush of tender growth that will be easily frost-killed and waste the plant’s energy.
  • And a warning from Larry: “The stress of drought increases trees’ susceptibility to diseases and insect attack, especially street trees; take pity on them and soak the ‘hell strip’ between the sidewalk (if you have one) and the curb with water at least once every couple of weeks.  Your grass can go brown and come back, but trees…even ‘native trees,’ are a lot healthier with water in the summer.”
  • Here’s another tip from Larry: “Trees dropping leaves or little acorns?  That is the plant adjusting to dry weather after a wet spring.  It’s normal.”
  • Don’t fertilize trees or shrubs.  Doing it in August (or any time after July) will stimulate new growth at a time when plants are beginning to enter dormancy, and could result in excessive winter damage.
  • Removing spent blooms on crape myrtles will encourage new growth and blooms.

Mums at Brookside Gardens

Perennials and Annuals

  • Starting August 15, it’s the season for mums and Behnkes will carry them in an assortment of colors, sizes and bloom types.
  • Miri reminds us of plants that can be planted now for blooms in August and later: “Don’t forget that you can have flowers from now until fall, too, not just great leaf color. Bluebeard shrubs bloom as early as this month, and many perennials do, too –  Aster, Boneset, Goldenrod and Ironweed are late-season butterfly magnets.  Japanese Anemone also blooms late, and their Asian brethren, Camellias, start showing off as early as October. Start planning now so you can grab what you want when fall restocking season hits.”
  • Hostas: bloomed-out flower stems should be cut off close to the base of the plant.  Hosta plantaginea and some white-flowered hosta cultivars such as ‘Royal Standard’ are going to flower in August.  They have fragrant flowers and are showier than the ones that have already bloomed, so even people who don’t care for hosta flowers may want to let these bloom.
  • Daylilies:  There are late-blooming cultivars of daylilies that haven’t started to bloom yet, so be careful not to cut off new bloom stalks. Old ones will be starting to brown, and may form seed pods.  From August through the fall is a good time to dig and divide your daylies (except for those late-blooming ones, of course).
  • Deadhead (remove faded flowers from) perennials unless they have showy seedheads, or seedheads that feed the birds (like that goldfinch magnet, the Purple Coneflower).
  • Keep feeding flowering annuals in containers for more  blooms.


  • The first week of September through October 15 is the best time to plant lawn seed – for a new lawn, lawn rejuvenation, to overseed a thin lawn or to fill in bare spots.  So August is a great time to reduce the weeds in your lawn, in preparation for the seeding you’ll be doing next month.

Vegetables and Herbs

  • From Sissy McKenzie: “August is the time to clean up the old vegetables in your garden and get ready for the new, so start thinking about your fall garden now.  In the fall garden you can have leafy vegetables, head vegetables, and underground vegetables.  Yes, around August 15th – September 15th it’s time to plant your fall vegetables.  Here are some of the fall vegetables you should look for:  broccoli, cabbage, Brussels sprouts, kale ( of many kinds), cauliflower, collards, mustard, turnips lettuce.
  • To harvest white storage potatoes on a cloudy, dig them the plants begin to die back, then let them lie on the ground for a few hours before bringing them inside. Don’t wash them – that can cause them to rot in storage. Store potatoes in a dark, cool location (35º- 40ºF.)”
  • Harvest watermelon on the vine after the first tendril next to the fruit has turned dark brown and there’s a yellowish white spot on the bottom of the watermelon. Harvest a muskmelon when it twists easily off the vine.
  • Peppers that are allowed to ripen on the plant may suffer from fungal disease, so pick them before they’re fully ripe.  Picking peppers while they’re still green also encourages plants to produce more fruit.
  • Tomatoes not bearing fruit in hot spells? It’s the heat. They stop setting fruit if night temps are over 80 degrees.


  • Keep spraying to protect choice plants from deer if you have to share your garden with them.
  • Insects thrive in dry, hot weather.  If a plant is just off-color, it may be dry and in need of watering, but it may also have spider mites.  Direct a strong spray of water under the leaves to wash them off, and repeat every couple of days.  Horticultural oil will help control them, but if sprayed onto a dehydrated plant or in hot, humid weather, it can burn the foliage, so follow instructions on the label.  Our garden shop folks probably have some other remedies they can suggest.
  • Keep your eyes open for shinny sticky leaves – on tropicals and assorted ornamentals (e.g., Euonymus and hollies).  This may be a sign of aphids and other sucking insects.  The shinny sticky stuff will turn to a black mold.  Both are harmless, only a sign that insects are feeding and they may need a strong stream of water, neem, or soapy water.
  • Be watchful of softball-sized brown patches on their Dwarf Alberta Spruce – a sure sign of spider mites.  One way to tell is by placing a white paper under a clump of foliage and rustling the branch, which will cause debris to fall on the paper.  Then look closely for signs of movement and if you DO have spider mites, grab your hose and vigorously spray the plant to knock off the spider mites.  Using water is cheap and it’s not a nasty chemical.
  • U.Maryland tells us that “Fall webworm is a 1-2 inch long hairy caterpillar that creates large tent like nests on the ends of branches of various shade trees and shrubs.  It’s unsightly but causes little damage. They can be left alone or knocked out of the tree with a broom, by a hard water spray, or pruning them out and disposing of them in the trasIf your periwinkle is wilting and turning brown from the fungal disease Phomopsis blight, simply prune away the infected plants.
  • Look out for Blossom End Rot on your tomatoes, cucumbers and melons – the opposite end from the stem will turn mushy and blackish brown.  This is a calcium deficiency problem that can be treated with Bonide Blossom End Rot Spray, which is a concentrated application of calcium.  Then next year when planting, apply an appropriate amount of lime (calcium carbonate) to your planting.  Additionally, the use of the fertilizer Tomato Tone helps prevent the problem because it’s 5% Calcium.

Photo credit for boy with sprinkler.

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