August Gardening Tips and Tasks

• Consider dividing and sharing perennial plants with people and gardens in your community. Late August through September is a great time to transplant, divide, and plant perennials. Save and share seeds from flowers that have finished blooming and have dry seed heads. See our three-part seed saving video series for seed collection and storage tips. Check with your local Master Gardener program for upcoming seed and plant shares.
• Plan to cover your vegetable garden soil with a cover crop. Crimson clover, winter rye, and spring oats can be planted from late summer to fall. This is one method you can use to improve your soil and make your garden more resilient to the impacts of climate change.

• August is frequently a dry month. Check the U.S. drought monitor map to see current conditions. Prioritize watering newly-planted trees and shrubs to help them establish a healthy root system.
• If you have room, try to add a new tree to your yard this fall. Shade trees help to cool the area around your home and mitigate the impacts of climate change. There are state and county rebate programs to help Maryland residents plant trees. Refer to the 5 Million Trees for Maryland page for more information.

• Harvest and preserve tarragon, rosemary, basil, sage, and other culinary herbs. Herb leaves are most intensely flavored right before the plant blooms.
• Harvest tomatoes when they first change color and let them ripen on a kitchen counter. This prevents many fruit problems (cracking, splitting, insect feeding, diseases) and increases the yield of edible fruit.
• There is still time to plant crops like kale, collards, leafy greens, and more. Take a look at our vegetable planting calendar.
• Now is a good time to purchase row cover fabric if you plan to extend your vegetable garden into the fall and winter months.
• Brown and green Southern stink bugs are active on tomatoes and peppers. They feed on the fruits, producing a yellow or white “cloudy spot” directly under the fruit skin. These spots become hard, but can be cut out with a sharp knife and won’t affect flavor.
• Remove and dispose of all rotted or dropped fruits and foliage from fruiting trees, vines, and shrubs. This will help reduce the overwintering of diseases and insect pests that can attack the plants next season.

Grass clippings and spent plants from the flower and vegetable garden provide a good source of high-nitrogen materials for the home compost pile. Fallen leaves and old straw mulch are good sources of high-carbon materials. Shred the materials with a lawnmower or string trimmer to speed-up the breakdown process. Keep sticks, large roots, and woody stems out of the compost pile because they take too long to break down and make it difficult to turn the ingredients.

• Cardinal flower (Lobelia cardinalis), smooth oxeye sunflower (Heliopsis helianthoides), mountain mints (Pycnanthemum spp.), and New York ironweed (Vernonia noveboracensis) are examples of native plants that bloom in August. You can find these perennial plants at native plant nurseries.
• Late August through September is a good time to transplant, divide, and plant perennials. Be sure to keep them well-watered during dry periods.
• Save seeds from flowers that have finished blooming. Label the storage container with the plant name and seed collection date.

• Avoid mowing the lawn during extremely dry and hot weather. Mowing wounds grass blades, creating more surface area for plant moisture to escape.
• Brown patch is a common fungal disease of tall fescue lawns that creates sparse brown areas. The lawn usually recovers on its own in the fall; no fungicide use is recommended. This disease is typically worse on over-fertilized and over-irrigated lawns.
• Submit a soil sample for testing if planning a lawn renovation project in the fall.

Beneficial insects

• Goldenrod soldier beetle adults are active. These beetles are both pollinators and predators: they feed on flower pollen and nectar as well as a wide range of insect pests. Support these beneficial beetles by planting late-season blooming flowers (like goldenrod) and by leaving fallen autumn leaves as leaf litter. The beetles typically lay their eggs in leaf litter, and it's also where the larvae (immatures) reside during the winter months.
• Monarch butterflies are producing their third and fourth generations. Fourth-generation monarch adults will make the long journey to Mexico, where they will overwinter. Fuel their migration by providing a diversity of late-season flowers. Check out this Monarch nectar plants for the Mid-Atlantic list for a list of recommended species.
• Robber fly adults are active. These predatory flies feed on a wide range of insect pests. Learn how to recognize these beneficial flies by their distinctive "bearded" face, a concavity between the eyes, long legs, and a typically long-tapering abdomen. Leaving some prey (pest insects) in your landscape can help to support and maintain robber flies and other predators.
• Eastern hercules beetle adults are active. These beetles help with woodland debris decomposition as the larvae (immatures/grubs) break down rotting wood and other organic material, and the adults feed on rotting fruit. As one of the largest insects in the U.S., they may appear intimidating, but rest assured these insects do not bite or sting; if held, their legs and toe claws may feel scratchy. Consider leaving (or creating) an area in the yard for fallen logs and woody plant limbs to support the larvae.
• Water strider adults are active and can be found on the surface of water bodies (ponds, streams, lakes, etc.). These predatory insects feed on other live and dead insects, including mosquito larvae. Conserve water striders by reducing the use of water pollutants like herbicides, fertilizers, and other pesticides and chemicals. Check out your local Master Gardener Bay-Wise/Water-Wise program for more landscaping practices and even landscape certifications.
• The adults and caterpillars of many giant silk moth species are active this time of year. Consider taking photos of local moths, eggs, and caterpillars for community science pages like iNaturalist. Conserve caterpillars by reducing/eliminating pesticide use and tolerating their feeding by leaving them alone.

Pests 

• Spotted lanternfly adults may be found feeding on many host plants, especially tree-of-heaven (Ailanthus altissima). If you observe spotted lanternflies, inform the Maryland Department of Agriculture (MDA) by reporting the sighting on their website. These insects are mainly nuisance pests in residential gardens and landscapes. They have not been shown to significantly damage otherwise healthy ornamental plants. Consider sustainable management options if you want to take action.
• Fall webworm caterpillars are becoming more abundant and are creating tent-like webbing on the ends of woody plant branches. Caterpillar feeding damage is usually minimal, and control is not typically needed; caterpillars are typically only active through October. Tents can be pruned out or left for natural predators like birds and parasitoids. Do not try to burn any webbed tents. Contact a professional if you would like to prune out a tent you cannot safely reach.
• Numerous caterpillars (including leafrollers, orange-striped oakworms, green-striped mapleworms, and oak skeletonizers) and sawfly larvae are feeding on various shade trees. Feeding damage is usually minimal, and control is not typically needed. These insects are an essential food source for birds. Some caterpillars have stinging spines or irritating hairs and should not be touched.
• European hornet adults are active. These predatory wasps can sometimes strip bark off of woody plants (especially lilac) to access sap and to obtain wood pulp for nest building. Most damage is minimal, but extensive bark stripping can girdle branches, leading to localized dieback. Fine insect mesh/netting can be placed over vulnerable woody plants. This species cab have several look-alikes; for wasp identification help, see our wasp identification guide or send photos to Ask Extension.
• Scale insects are best controlled during their vulnerable crawler stage (newly-hatched juveniles). Some species of scale, like crapemyrtle bark scale, will begin hatching this time of year. Monitor for crawlers, particularly on plants with a history of scale infestations. Specific controls and the timing of their use are based on the scale species. Use Ask Extension for scale insect identification help.
• Many different types of leaf and stem galls are present. Galls are abnormal swellings of plant tissue typically caused by arthropod feeding or egg laying. These galls do not significantly harm plants, and control is typically not needed.
• Cabbage looper and imported cabbageworm caterpillars and adults are active; both species have at least two generations per year. Check host plant leaves (mainly crucifers/brassicas) for signs of feeding damage and for the presence of caterpillars and droppings (frass). Found caterpillars can be removed and destroyed. The biopesticide Bacillus thuringiensis (Bt) or horticultural oil can be used with heavy infestations, following all product label instructions.
• Aphids may be abundant. Allow naturally-occurring predators like ladybugs, lacewings, flower flies, and parasitic wasps to control the aphids. Strong water sprays can also help to knock aphids off of the plant and reduce outbreaks. Avoid over-fertilization with nitrogen, as studies have shown that quick-release, high-nitrogen fertilizers can boost aphid populations. Horticulture oil can be used on heavy aphid infestations.
• Colorado potato beetle adults are active and feeding before they enter diapause (similar to hibernation) for the winter. They are typically found on eggplants, potatoes, peppers, and tomatoes. Adults or larvae can be picked off the plant and put into a container of soapy water. Placing row covers over host plants can help exclude the adults. Tilling under host plants in the fall or winter can help expose and kill overwintering adults in the soil.
• Squash bug adults and nymphs are active on cucurbits. Place row covers over host plants to exclude adults and prevent egg-laying. Monitor for adults, eggs, and nymphs (immatures). Adults and nymphs are great at hiding out of sight, sheltering under leaves and mulch. Adults and nymphs can be brushed off the plant into a container of soapy water. Leaves with egg clusters can be removed and destroyed, or the eggs brushed off the leaf or squished.
• Squash vine borer adults and larvae are active. Cover squash plants with row covers until they flower; remove the cover during flowering to give pollinators access. Monitor for squash vine borer entry holes and frass (fecal matter). Infected plants may be saved by carefully slicing and removing larvae within the stem and placing moist soil over the split vine. Remove and destroy any plants killed by squash vine borers.
• Harlequin bug adults and nymphs are active, typically found on crucifers/brassicas. Nymphs and adults can be brushed off into a container of soapy water.
• Mosquitoes are abundant. Patrol the yard for mosquito breeding sites. At least twice a week, check and remove water that may be ponding in trash and recycling cans or lids, flowerpot saucers, children and pet toys, wading pools, tires, tarps, or plastic sheeting. Reconsider mosquito sprays/fogs that can harm beneficial insects. Since mosquitoes are not strong fliers in a sturdy breeze, fans can be used to deter mosquitoes from outdoor porches.

• Southern blight, a significant soilborne disease, is promoted by hot and humid weather. The fungus attacks a wide range of annuals, groundcovers, and perennials, including thyme, coneflower, coreopsis, and black-eyed Susan. Affected lower stems turn brown or black, the foliage wilts, and plants will eventually dry up and die.
• Remove hosta leaves that are yellowing or scorched (brown leaf margins). In many cases, this is caused by a combination of hot, dry conditions, and diseases like alternaria and anthracnose (Colletotrichum). If symptoms are caused by an infection, leaf removal will help to slow down disease progression.

• Propagating African violets is easy using leaf cuttings. Place the cuttings in a soilless mix labeled for African violets. Keep the cuttings moist (but not soaking wet) and place them in a brightly-lit location or under fluorescent lights.
• Brown scale are sucking insects that attack a wide variety of plants but are common on Ficus and indoor citrus plants. Heavy infestations may cause leaf yellowing, stunting, and dieback. They are difficult to control when abundant.

• Fruit flies can be a problem when fruits and vegetables are allowed to sit for long periods on kitchen counters. Don’t leave fruit on the counter for more than a day or two, thoroughly rinse recycled containers, and be on the lookout to eliminate anything that holds moisture (including mops and sponges).
• Contact a pest control professional if yellowjackets are nesting inside the walls or attic of your home or a structure.
• Always be on the lookout for signs of termite damage such as the presence of dirt tunnels or "shelter tubes," soil packed in cracks or crevices, cracking or sagging floors, dark or blistering wood paneling, and/or blistering or peeling paint on wood. Contact a professional pest control company if you suspect there are termites inside your home. It is generally recommended to contact multiple companies so you can compare prices and treatment plans. Most companies provide free estimates, at which time they discuss a treatment plan, cost, and of equal importance, warranties. Companies that are members of the Maryland Pest Control Association and the National Pest Management Association have access to all current treatment practices.