August Garden Calendar

Trees & Shrubs

General
As weather becomes hot and dry, deeply water any trees or shrubs that have been planted within the past year. Prune all dead, damaged, or diseased branches any time of the year. Other pruning of trees and shrubs should wait until cooler weather in November. Roses are an exception; most can be pruned in August. However, do not prune Old English rose varieties in the fall — prune in the spring if at all.

Cercospora Leaf Spot
This one often afflicts hydrangea. The disease first appears as small purple leaf spots on the upper surface of the leaf. Dispose of fallen leaves. Fungicides are used only in extreme cases.

Septoria Leaf Spot
There are various Septoria leaf spot fungi that cause leaf spots on a number of woody plants later in the summer, often on dogwood. Septoria leaf spot initially appears as dark brownish purple leaf spots often with gray centers. On dogwoods, spots are larger than spot anthracnose, typically 1/4″ across. They are irregular or square shaped (often bound by leaf veins). Spots can coalesce into larger blotches.

For more information on pests and diseases of August see the August Diagnostic Lab Preview.

Lawn

Mowing
If your cool season grass is not growing, don’t mow it. If it is growing, cut it high. Three inches or higher is a good cutting height for Kentucky bluegrass perennial ryegrass and tall fescue.Warm season grasses love the hot weather. Mow zoysiagrass and bermudagrass to 1-2 inches.Use a mulching mower, and leave the clippings on the lawn to return nutrients to the soil.

Cool Season Grasses
August is a great time to begin renovating your cool season lawn. See our feature Lawn Renovation Part 1: Making Choices.Check for lawn diseases if you see brown patches, brown rings or cottony white growth on your lawn. This may indicate Leaf Spot, Dollar Spot, or Brown Patch disease. Bring samples of healthy and diseased grass to a FCMGA plant clinic for diagnosis and recommended treatment.August is still the season to treat for white grubs. If you suspect there is a grub problem, (many Japanese beetles in your yard is usually a good indication), use a spade to remove a square of turfgrass a foot long and wide and 1-2 inches deep. If you count six to 10 grubs in the soil, you are justified in treating for grubs. However, remember that insecticides harm beneficial insects as well as pests. Use a product that is labeled to control white grubs and follow label directions.Take care in applying selective weed-killers in hot weather because they may damage the turfgrass and surrounding plants. Best to wait until cooler weather to apply broadleaf weed-killers safely.

If the weather becomes dry in August, irrigate at the rate of one inch of water per week in the early morning to maintain green. Infrequent, deep watering is best. If you choose not to irrigate and allow the lawn to go dormant, it will likely green up again in September.

Do not fertilize this month.

Warm Season Grasses (zoysiagrass, bermudagrass)
You may fertilize until to mid-August. Apply 0.7 pound of water soluble nitrogen per 1000 square feet of lawn every three to four weeks. Do not exceed a total of 2.1 pounds of nitrogen per 1000 square feet during the season.

Vegetable Garden

Watering is the most important task for the vegetable gardener. Plants need an inch of water and should receive it all at once. This should wet the soil to a depth of 6-8 inches. Hand watering the plants using a shower-like spray at the end of your hose allows for watering the ground without getting water on the foliage. It also allows you to target the water directly to the plants. Another good alternative is to use drip irrigation to target the water. If you do overhead watering with a sprinkler, make sure you do it very early in the morning so the sun and heat of the day can evaporate the water from leaf surfaces. Mulch keeps the soil cool and keeps the moisture in.

Don’t leave eggplant on the vine too long. When the seeds become brown and hard, the eggplant is overripe and not of good quality for eating.

Vine crops like cucumber and winter squash will continue to grow for the entire growing season unless stopped by disease or insects — or the gardener. Grow cucumbers on a trellis to save space and keep the cucumbers off the ground. Pinch off the fuzzy growing tips of the vines to cause the plant to direct its energy to make fruit instead of growing stems and leaves. You can pinch off winter squash vines the same way although use of a trellis with winter squash is not practical because the fruit are too heavy.

When you store carrots after harvest, make sure to remove the green tops to prevent the carrots from becoming too dry. The tops of harvested carrots transpire just as they do when the plant is in the ground.

Leave 2-3 inches of stem on winter squash and pumpkins when you harvest them. They will keep longer in storage.

Remember to check your summer squash and zucchini plants daily during the harvest season. The fruit grow very fast and can easily become too big for use at the table.

Early August is the last time to plant beans for fall harvest. Lettuce, cabbage, broccoli, and cauliflower can be started as seeds for late August transplant to the garden.

Fruits

Continue to water strawberries, blueberries, and bramble fruits in August and September even after you have completed the harvest. This is the time of year the plants are setting buds for next year’s fruit. Do not allow these buds to shrivel.

Strawberries should be fertilized in August. If the plant was set out this spring, use 12 to 18 ounces of 10-10-10 per 25 feet of row. If the plant is in its second year use 18 to 24 ounces of 10-10-10 per 25 feet of row. Make sure to brush any fertilizer off the leaves to prevent burn.

On your apple and pear trees dead branches with leaves still attached may indicate that they have been hit by fire blight. Prune off these dead limbs and make sure to cut at least 8 inches below the dead area. Dispose of the pruned limbs in the trash. Sanitize your pruners or saw with 10% bleach solution or – better yet – with the original formulation of Lysol (contains o-benzyl o-chloro phenol).

Pick up and destroy all fallen fruit from your fruit trees. This will go a long way toward preventing insect and disease infestations next year.

Diseases that commonly occur in August:
Peach scab: the primary damage is to the fruit. Small olive green spots appear on fruit, usually on the stem end. Spots enlarge and darken. The spots become corky, preventing the skin from expanding as the fruit grows, creating openings for other fungal infections. Preventive treatment needs to be applied in early spring.

For more information on pests and diseases of August see the August Diagnostic Lab Preview.

Flowering Annuals, Perennials

Remove spent flowers of cosmos, zinnia, marigold, scabiosa, and others to maintain plant vitality and keep them flowering. Before using any pesticide, make sure you have properly identified the disease or pest. FCMGA plant clinics and Diagnostic Lab are at your service for this purpose.

Diseases that commonly occur in August:
Phytophthora on Liriope
Leaf and crown rot on can infect any liriope cultivar, though ‘Evergreen Giant’ seems the most susceptible. This disease is spread by water in the soil. Root systems of affected plants are often much-reduced and severely damaged. Infected plants cannot be saved and should be dug out and destroyed.

Phytophthora on Annual Vinca
Annual vinca can get an aerial stem blight (i.e., an infection on parts of the plant above the ground) and a root and collar rot. The aerial stem blight begins on the stems and is encouraged by wet foliage. Plants with stem blight sometimes also have the root and collar rot, which starts in the roots and is encouraged by wet soil.

Phytophthora root and crown rots will also infect snapdragons, petunias, Calibrachoa, and Christmas cactus (Schlumbergera spp.) among many others.  Exceptionally wet weather in late spring and early summer provide optimal conditions for these water mold diseases.

For more information on pests and diseases of August see the August Diagnostic Lab Preview.

References
A Guide to Successful Pruning, Shrub Pruning Calendar, VCE Publication 430-462
A Guide to Successful Pruning, Deciduous Tree Pruning Calendar, VCE Publication 430-460
A Guide to Successful Pruning, Evergreen Tree Pruning Calendar, VCE Publication 430-461
Mowing To Recycle Grass Clippings: Let the Clips Fall Where They May, VCE Publication 430-402
Maintenance Calendar for Cool-Season Turfgrasses in Virginia, VCE Publication 430-523
Maintenance Calendar for Warm-Season Lawns in Virginia, VCE Publication 439-522
Spring and Summer Lawn Management Considerations for Cool-Season Turfgrasses, VCE Publication 430-532
Vegetable Planting Guide and Recommended Planting Dates, VCE Publication 426-331
August Tips, Vegetables, VCE Publication
August Tips: Fruit and Nuts, VCE Publication
Annuals: Culture and Maintenance, VCE Publication 426-200
Tree Fruit in the Home Garden, VCE Publication 426-841
Small Fruit in the Home Garden, VCE Publication 426-840
Tomato Questions, Texas A&M Extension Publication