Ask the Expert: Get Advice for Your Late Summer Garden

Lucy Mercer
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Late Summer Gardening | The Home Depot's Garden Club

A late summer garden is just as challenging as an early spring garden, where a lengthy to-do list and a ticking clock on ever-warming temperatures keep you prepping and planting. By August, your vegetable and flower gardens should be at their peaks. While maintaining them at the height and heat of the season, you can make preparations for your fall garden planting.

We asked gardening experts for advice on gardening in the late summer. 

“Gardeners are adaptable, we have to be,” says perennial expert Ruth Rogers Clausen, horticulturist and author of many books, including “50 Beautiful Deer-Resistant Plants” (Timber Press). And that means that we adapt, so in the summer garden, you can prepare, prune and plant perennials even through the hottest days of August. 

Expert Tips for the Late-Summer Flower Garden:

 

Dahlias are summer bulbs to plant in spring ll The Home Depot Garden Club

1. Deadhead and prune to rejuvenate plants

Deadheading, or removing spent blooms to keep the plant from setting seed, keeps plants blooming longer. Dahlias, in particular, need to be trimmed down to the branch. “Don’t just pop the top,” Clausen advises. More plants that benefit from a trim are gaillardia (blanket flower), ligularia, roses, perennial sunflowers and Montauk daisies, which thrive in the sandy soil near her garden on the coast of Maryland.

To keep plants manageable, prune severely early in the season for shape and size. For overgrown perennials like sedum ‘Autumn Joy’, Clausen recommends “a good haircut,” or trimming to half its height. Take the cuttings and put them in good quality potting soil to start more plants.

 

Asters in the Late Summer Garden | The Home Depot's Garden Club

2. Refresh beds and borders

Use low-growing favorites like asters to give new life to border plantings, like the Mexican feather grass ‘Pony Tails’ featured above. Asters are pollinator magnets, so look for native selections to attract butterflies to your garden.

Fall-blooming bulbs will also add color and texture to your flower border. Slip colchicum, autumn crocus, into the ground for late-fall blooms. Hardy cyclamen are another good choice for dry shade gardens. (photo by Ruth Rogers Clausen)

 

Groundcovers in the late summer garden | The Home Depot's Garden Club

3. Cover some ground

Ground covers like the plumbago (leadwort), above, soften the edges of borders and carry color into the fall. They will bloom more as the heat wanes and nights cool off. They can be planted late in the season, but be prepared to keep them watered until established, Clausen says.

 

Ornamental Edibles in the Fall Garden | The Home Depot's Garden Club

4. Edibles as ornamentals

In early summer, tender garlic chives can be harvested and used as an herb. Late in the summer, as they bolt, or flower, they become a striking ornamental, appreciated by gardeners for their masses of airy, white blooms. The pollinators will appreciate the chives, too.

Expert Edible Garden Tips:

Managing heat is the number one concern for vegetable gardeners in late summer, according to edibles expert and garden writer Teresa Woodard, who gardens near Columbus, Ohio.

 

Tomatoes | The Home Depot's Garden Club

1. Keep edibles watered

“Heat creates stress in the garden,” Woodard says, “and it’s important to evenly water vegetables, especially tomatoes, because they’re fruiting.” Inconsistent moisture leads to cracking tomatoes, blossom end rot and other problems.

An inch of water a week is recommended for most gardens. In a heat wave, you may need to water more often. Be sure to water in the cool of the day, just before sunup, if possible. A digital hose timer set up with a soaker hose makes that easy. 

Fall Vegetable Gardening with Row Cover | The Home Depot's Garden Club

2. Throw shade

Now is the time to plan for fall crops of cool-season vegetables like lettuces, kale, radishes, carrots and quick-maturing beets. The trick is to get them to germinate in the heat, Woodard says. 

Her advice is to keep plants watered, and plant new seedlings near a taller vegetable that can provide shade, like lettuces planted near beans, for example. You can also use a board or row cover to shade plants until established. 

 

Lettuce in the Fall Garden | the Home Depot's Garden Club

3. Explore foodscaping and refresh annuals

As the days cool off, have fun and experiment with lettuces and ornamentals like pansies, advises Woodard. Sow seeds every week to have a succession planting of greens for salads. The yellows and oranges of late summer pansies make a bright contrast to the green and red lettuces.

 

4. Harvest early, harvest often

Carrots and other root vegetables can be a challenge in Midwestern clay soils, Woodard says. She recommends looking for ‘Nantes’ and ‘Tom Thumb’ seed varieties for quick-growing, shorter roots. And, if the harvest is just taking too long, you can always pick them as “baby” vegetables and serve them in a salad or as a garnish. 

By harvesting early, you can plant successive crops to be harvested right up until, and sometimes past, the first frost. Sturdy greens like kale and collards are sweeter after a frost.

 

Japanese beetle in the summer garden | The Home Depot's Garden Club

5. Scout for pests

Be diligent about looking for pests that find your vegetables. When you water your plants, turn over the leaves to see if there are any infestations or evidence, like holes nibbled in the leaves.

Some damage by Japanese beetles can be controlled without pesticides. The best approach, Woodard says, is to wait and see if the beetles will move out of your garden on their own. But if the damage passes your threshold, you can take a bucket of soapy water into the garden, pluck the pests off your plants and drown them in the sudsy water. 

Row covers will protect your plants from some pests, and if you keep backyard poultry, you know that your flock will protect your edibles, too.

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