Continue to keep newly planted trees and shrubs well-watered.
Clean up fallen rose and peony leaves. They can harbor disease and insect pests over the winter if allowed to remain on the ground.
Refresh mulch, check for weeds and water landscape beds.
Take a break from the heat and take time to enjoy your landscape.
Scout for diseases on roses. Treat with fungicides if necessary.
Keep an eye out for spider mites on ornamentals! They love it hot and dry. Frequent, strong jets of water can help reduce mite populations.
Avoid pruning shrubs and trees now. Pruning now will promote new growth that will not harden by winter which can lead to winter damage.
If azaleas look chlorotic (pale green to yellow), check the soil pH. They need an acid soil. Scout for insects as they can cause yellowing also.
Keep deadheading annuals and perennials as needed.
Annuals may be cut back to encourage a new flush of growth and blooms.
Do not fertilize roses after August 15th.
Powdery mildew on lilacs, phlox and zinnias is unsightly, but causes no harm and rarely warrants control.
Start ordering spring flowering bulbs but wait to plant them until fall.
Divide iris after bloom.
Many herbs self-sow if the flowers are not removed. Dill, lemon balm, oregano, basil, and cilantro seeds fall around the parent plant and come up as volunteers the following spring.
A cover crop adds organic material when it is incorporated into the soil the following spring. Later this month, plant a winter cover crop to enrich your garden soil. Wheat, cereal rye, and red clover are good choices. Plant no later than November 1st.
Fall vegetables can be planted until late in August. Vegetables include lettuce, radishes, cabbage, broccoli, cauliflower, spinach and turnips. For planting dates, see MU Extension Guide G6201 Vegetable Planting Calendar https://extension2.missouri.edu/g6201.
Compost plant materials from the garden as crops are harvested. Avoid composting any plants that are disease or insect infested. Avoid any weeds that have went to seed. Practice good sanitation measures. For more information on composting, see MU Extension Guide G6956 Making and Using Compost https://extension2.missouri.edu/g6956.
Cure onions in a warm, dry place for 2 weeks before storing. Store in a cool, dry place. for more information, see MU Extension Guide G6226 Vegetable Harvest and Storage https://extension2.missouri.edu/g6226.
Water garden vegetables thoroughly in times of drought.
Scout for insect and disease problems in the garden. If you use a pesticide, follow the directions on label.
To reduce the number of pests on your fruit tree for the coming year, pick up and discard spoil fruit on the ground.
Heavy rains at harvest can dilute the sugars in melons. Watermelons can re-concentrate the sugar if left for a few dry days however cantaloupes cannot do this.
Scout for fall webworm activity in fruit and nut trees.
Prop up branches of fruit trees that are threatening to break under the weight of a heavy crop.
Check peach tree trunks just below soil line for a gummy mass caused by borers. Treatment may be required.
Continue to spray ripening peaches to prevent brown rot.
Harvest cantaloupes when the melons pull easily from the stem; watermelons when there is a hollow sound when thumped and the skin loses it's shine; honeydews when the blossom end is slightly soft or springy.
Harvest early season apples when the undercolor turns from green to red.
Grape harvest begins.
Tall fescue and/or Kentucky bluegrass
Late July and August are traditionally the toughest months for growth of tall fescue and Kentucky bluegrass. Temper expectations of a perfect lawn in these months realizing that fall is the best time for recovery.
Mow frequently enough to compensate for growth. Non-watered or stressed lawns may not grow quickly during this time. If the lawn isn't growing, then don't be mowing.
If possible, keep lawns watered in times of drought with deep, infrequent watering. If not watered, expect drought dormancy and restrict mowing to compensate.
Brown patch and other diseases can severely affect tall fescue in this time frame. Later in August, gray leaf spot can also be prevalent. If fungicide use is desired, azoxystrobin has been found effective on brown patch, but alone may not work on gray leaf spot.
Fall seeding and sodding is best. Think about preparing the seedbed in mid-late August. Remember that overseeding is a good way to rebuild density and turfgrass quality.
Have soil tested if you are unsure of liming needs or basic fertility level of nutrients such as phosphorous, potassium, and calcium. Nitrogen is a constant need for lawns and soil tests will not provide guidance.
Select and purchase grass seed and fertilizer. At a minimum, plan on applying 0.5 - 1 lb of N/1000 sq ft of lawn around mid-September. Potassium may also be incorporated at a third to half of that total. Application of other nutrients should be guided by a soil test. For guidance, see http://agebb.missouri.edu/fertcalc/.
If lawns are to be totally renovated, kill all vegetation with a non-selective herbicide application (i.e. glyphosate) near midmonth. If trying to kill Bermuda grass, apply glyphosate on Aug. 1 and again one month later.
Fertilize warm-season lawns with 0.5 - 1 lb N/1000 sq ft. A fertilizer with some potassium may also help with winter tolerance. A ratio of 24-0-12 or similar would deliver both nitrogen and potassium. For guidance, see http://agebb.missouri.edu/fertcalc/.
Mow frequently enough to compensate for growth. In drought conditions when turf is growing more slowly, restrict mowing.
August is not the best time to establish warm-season turfgrasses. Little time is available for plant growth prior to limiting cooler temperatures. Solid rooting and establishment are critical prior to winter to prevent winterkill.