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What to do in the garden in July & August

It is the heart of summer gardening season. The Northeast sees its hottest weather in July but, August can bring hot, humid weather as well and can be unpredictable, with extended periods of rain and even cooler temperatures as garden stands begin to show pumpkins and fall mums. Below we provide you with some gardening tasks to help keep your gardens flourishing through the late summer.

Step back and look at your garden to see what is in bloom and where you lack floral color. It is the perfect time to take pictures and notes as to where you can improve next year.

Make sure tall plants and climbers are well supported in case of bad weather. Also, pruning wisteria at this time will encourage new growth and help keep it in balance with the trellis.

Water at dusk to reduce evaporation; mulch garden beds to retain moisture around plants and help keep roots cool. Always practice effective watering by watering the soil around the base of the plants rather than the foliage. Control water and sprinkler use so as not to waste water by losing it to pavement, driveway, or any other unintended area.

Newly planted trees and shrubs (deciduous and evergreen) need extra watering in dry periods. Make sure they get a good, regular deep drink that will go down to their roots. Keep an eye on them for signs of wilting, a sign they are lacking water.

Do not mow too low in summer. Mow as high as possible—that will result in a healthier lawn with deeper roots that are more tolerant of the drought and stress of summer. Slightly higher turfgrass also helps shade out the weeds. 

Regularly deadhead annual and perennials as well as roses to encourage new blooms. Cut back faded perennials to keep gardens neat. Some spring blooming perennials, such as lupine, can be sheared back hard to encourage a second flush of blooms later in the summer. Now is the time to cut back any remaining spring bulb foliage as well.

Keep containers fresh.

Check your containers. Cutting back growth in hanging baskets (i.e., petunias) can encourage new flowers and foliage to revive the display; fertilize well after doing this. Make sure you are fertilizing your containers regularly throughout the hot months. When it comes to container plants, remember the soil dries out faster, so pay special attention to make sure these plants are receiving sufficient water. Terracotta pots will particularly dry out quicker, so dampen the pots to reduce evaporation and help keep the plants roots cool.

Consider dividing bearded iris now. If your plants did not bloom well, chances are they need to be divided. July through August is the best time to do this. Using a digging fork, carefully dig around the plant, being careful not to pierce the rhizome. Once lifted, shake off loose soil or rinse it off with a hose so that you can better inspect the rhizomes for any damage. Separate the individual rhizomes. Cut the foliage to about six inches. Cut sections of the rhizome so that you have pieces about three inches long with healthy roots growing from the cut, using a sharp knife to make clean cuts. Replant, being careful not to bury the rhizome with more than an inch of soil; these plants will not bloom well if planted too deeply.

Avoid transplanting roses when the temperatures are above eighty degrees. If you do transplant them in summer, prune heavily. Water the roses slow and deep. Add mulch to help suppress weeds. 

Harvest vegetables and fruits regularly; July is a good month to harvest beets, peas, carrots, chard, lettuce, and some tomatoes. Routinely inspect your vegetable garden and prune any yellow foliage. Remove garden debris to cut down on insect or disease issues. Continue to remove suckers from tomato plants and check that they are adequately supported with stakes or cages. Water crops daily in hot weather to ensure they are consistently moist. Uneven watering may cause blossom end rot on tomatoes. Blueberries are especially sensitive to drought conditions. Feed crops with a general-purpose fertilizer. Weed regularly, since weeds can compete with your crops for nutrients and water.

In late July, consider a fall crop of snow peas, spinach, or lettuce. Other cool season crops do well in mid to late summer to give you a nice fall harvest.

Observe your garden daily. If you see a harmful pest consider integrated pest management practices: cultural, biological, and mechanical controls. Use chemical controls as the last resort. Handpick Japanese beetles using a pail of soapy water. Just hand pick or shake plants and the pests will just fall into the bucket and drown. Look at the undersides of plant and crop foliage where insects such as aphids can hide. Keep an eye out for the scarlet-colored lily leaf beetles on your ornamental lilies. Check for sticky brown larvae on the undersides of lily foliage. 

Protect bramble crops such as blackberries or raspberries from birds by installing netting around the plants.

Shrubs may require some pruning to give much needed shaping and to allow good air circulation at this time. 

Look at your containers; if they are looking a bit shabby, consider a container rehab! You can use houseplants, individual plants from the garden bed, plants from other containers, or plants on sale to give your container a fresh look. Carefully pull out those that are past their peak and replace them with fresh plants. Be sure to fertilize after replanting.

After the month of August, cease fertilizing your roses—this will help to prepare them for fall and winter months ahead.

Think about which bulbs you might like to add to your garden for next spring. Now is the time to order them. In late August, you can plant fall-blooming bulbs such as colchicums or autumn crocus as soon as they are available.

Make notes on your garden’s pros and cons. Take more photos of your garden. Do you want to make any changes or additions? Garden centers will be having sales and it could be a good time to add plants. It is a great time to plan for next year.

In a Zone 5 garden, August is the latest to consider growing edible crops for the fall such as lettuce, spinach, or broccoli. You may have to consider protecting them from the hot sun by using row covers or milk crates.

Keep mowing your lawn high. Late August into September is the perfect time to renovate a tired lawn or start a new one.

Harvest beans, cucumbers, zucchini, eggplant, peppers, tomatoes, etc. so that plants continue to produce. Peppers can stay on the plant longer to allow them to color. Consider what to do with your herbs; it is a good time to freeze or preserve them in other ways for use over the winter months.

Take cuttings of your favorite annuals such as coleus, impatiens, or geraniums. You can grow them indoors later to save for next year. Many plants, such as coleus, will easily root in a glass of water.

Consider adding a perennial fruit or fruit tree to your garden. The upcoming fall is the perfect time to plant and stock may be available on sale and could be a good money saver.

Feel free to reach out to your local Cornell Cooperative Extension office’s Master Gardener volunteers for answers to any questions you might have.

— Rosanne Loparco, John Slifka, and Ron Broughton, Master Gardener volunteers at Cornell Cooperative Extension, Oneida County

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