The dog days of summer are July 3rd to August 11th. The Greeks, Romans and Egyptians believed that Sirius, the dog start, added its heat to that of the sun, causing the hot weather. Dog days are not particularly advantageous to any plant or creature. The keys to plant survival this month and the next are water and mulch—and diligent deadheading.
Lawns. To prevent wilting and drought stress, wet the soil to a depth of 4-6" every 5-7 days. Hold back fertilizer during July and August. Grass should not be closely cut in hot, dry weather.
Trees/Shrubs. Check evergreens for scale and bagworms. Make sure tree and shrubs planted within the past year are receiving at least 1" of water weekly. With fall plant catalogs arriving in the mail, consider what you might add (or subtract) from the landscape.
Annuals. Soak garden thoroughly at least once weekly. Spray zinnias and others with a fungicide at the first sign of mildew, following container instructions regarding repeat treatments. Start seeds for biennials such as foxglove and Sweet William. Containers and hanging baskets may need to be watered more than once a day. Start cuttings of begonias for house plants this winter.
Bulbs. Order now for fall planting before they run out of your first choices. Consider the amount of bulbs you order - a lot of bulbs means a lot of digging.
Perennials. Stop pinching chrysanthemums about July 15th. For specimen blooms give an additional feeding of 1/3 cup commercial fertilizer 6-12-12 about July 15th and water well. Spray phlox with fungicide. Deadhead. Cut broken and withered fronds of ferns to the ground. You can still plant daylilies. Prune hedges.
Roses. Increase the interval between black spot sprays. Watch for spider mites. Fertilize. Water as needed.
Herbs. Keep pinching back your flowering herbs like basil, oregano and mint to prevent them from flowering and going to seed. You can use or store your trimmings. Dill, mint, oregano, rosemary, sage and thyme dry well. Chervil, cilantro, parsley and tarragon are better when frozen.
Vegetables. Harvest promptly for peak flavor, freshness and before the insects get to ripe vegetables. Plan your fall planting. If you don’t garden or need more produce to put back, consider patronizing your local farmers’ market.
Fruits/Berries. Blackberries are ready to harvest when they become soft and juicy. Thornless blackberries are ready to pick when they lose their glossy appearance. Cut all raspberry canes that have finished fruiting to the ground.
In General: Summer months require more watering. Applying water at the ground level minimizes evaporation and places the water where it is needed - in the soil. Soaker hoses, bubbler attachments and drip irrigation are all efficient systems. If using overhead sprinklers, water early in the day to minimize evaporation and allow time for leaves to dry. Leaves that remain wet overnight are susceptible to disease. Avoid letting plants get to the wilting point, because wilting weakens overall plant health. Water deeply if soil is dry a few inches into the soil. Water display pots until water drains out the holes at the bottom. Container plants always dry out more rapidly than garden plants, often needing daily watering. Keep new transplants well watered until established in the garden. Even drought tolerant trees and shrubs need watering through their first two years to help them become well established.