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.
   
• Make a plan to add a new tree to your garden this fall, if feasible. 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 trees, vines, and bushes. This will help reduce the overwintering of diseases and insect pests that will attack your fruit plants next season.

• Grass clippings and spent plants from the flower and vegetable garden provide a good source of high nitrogen green materials for the compost pile. Fallen leaves and old straw mulch are good sources of high carbon brown materials. Shred your materials with a lawnmower or string trimmer to speed up the breakdown process. Keep sticks, roots, and woody stems out of your compost pile. 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 some 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.

• Avoid mowing your 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 thin, brown areas. Grasses will green up and recover in the fall. No chemical controls are recommended. This disease is typically worse on over-fertilized and 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 feed on pollen and nectar as well as a wide range of insect pests (a pollinator and a predator). Support these beneficial beetles by planting late season blooming flowers like goldenrod and by leaving the leaves as leaf litter is where they typically lay their eggs and where the larvae (immatures) reside during the winter months. 
   
• Monarch butterflies are producing their third and fourth generations. Fourth generation monarch will make the long journey to Mexico where they will overwinter. Fuel their journey by providing a diversity of late season blooming flowers. Check out this plant list for monarch nectar plants recommended for our area.
   
• Robber fly adults are active. These predatory flies feed on a wide range of insect pests. Learn how to spot these beneficial flies by their distinctive "bearded" face, concavity between the eyes, long legs and typically long tapering abdomen so you can leave them be. 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 decomposition as the larvae (immatures) 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 can be scratchy. Consider leaving or creating an area 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, pesticides, and other chemicals. Check out your local Master Gardener Bay-Wise/Water-Wise program for more landscaping practices and even landscape certifications. 
   
• Many giant silk moth species are active (adults and caterpillars). 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 be. 

Pests 

• Spotted lanternfly adults may be found feeding on many host plants, especially tree of heaven (Ailanthus altissma). 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 (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 and wasp larvae, including leafrollers, orange-striped oak worms, green-striped maple worms, oak skeletonizers, and sawflies 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. Leave caterpillars be as some have stinging or irritating hairs. 
   
• 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 branch dieback. Netting can be placed over vulnerable woody plants. This wasp species can have many look-alikes. For identification help, see our wasp identification guide or send photos to Ask Extension.  
   
• Scale insects are typically best controlled during their vulnerable crawler stage (when their eggs hatch, the immatures are called crawlers). 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. Specific controls and timing are based on the scale species. Use Ask Extension for 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 moths are active (both species have two or more generations a year). Check host plant leaves (mainly crucifers and brassicas) for signs of feeding damage and for the presence of caterpillars and caterpillar droppings (frass). Found caterpillars can be removed and destroyed. The biopesticide, Bacillus thuringiensis (B.t.) or neem oil can be used with heavy infestations, following all label instructions.  
   
• Aphids may be abundant. Allow local predators like lady beetles and parasitic wasps to control the aphids. Strong water sprays can help knock off aphids and decrease populations. Avoid high nitrogen, quick releasing fertilizers as studies have shown these 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 ("hibernation") for the winter. These beetles are typically on eggplants, potatoes, peppers, and tomatoes. Any found adults or larvae can be placed into a container of soapy water. Placing floating row covers over any host plants can help exclude adults. Tiling 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. Place floating row covers over any host plants (cucurbits) to exclude adults and prevent egg laying. Monitor for adults, eggs, and nymphs (immatures). Adults and nymphs are great hiders, hiding under leaves and mulch. Adults and nymphs can be brushed off into a container of soapy water. Leaves with egg clusters can be removed and destroyed. 
   
• Squash vine borer adults and larvae are active. Cover squash with floating row covers until they flower; remove them during flowering to allow for pollination. 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 and brassicas. Nymphs and adults can be brushed off into a container of soapy water.
   
• Mosquitoes are abundant. Patrol your yard for mosquito breeding sites. At least twice a week, check and remove water that may be standing in trash and recycling cans, flower pot saucers, children and pet toys, wading pools, tires, tarps, or plastic sheeting. Reconsider mosquito sprays/fogs that can harm beneficial insects. Fans can be used to deter mosquitoes from outdoor porches.

• Southern blight, a significant soil-borne disease, is promoted by hot and humid weather. It attacks a wide range of annuals, groundcovers, and perennials including thyme, coneflower, coreopsis, and black-eyed Susan. Affected lower stems turn brown or black, 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, or diseases like alternaria and anthracnose (Colletotrichum). If disease-related, 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.

• 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, even 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.