Monthly Gardening Calendar
Sharon Morrisey, Consumer Horticulture Agent
Milwaukee County UW-Extension

Between the mosquitoes and the heat, the garden in July is better enjoyed through a window. Quick forays to harvest vegetables or cut flowers may be possible mid-day if there’s at least a light breeze. Longer sessions will require application of insect repellent or long sleeves and pants.

Of primary concern are weed control, pest management and timely harvesting of vegetables. Vegetable gardens and flower beds benefit from a thick mulch layer of an organic material to help retain moisture, suppress weeds and moderate soil temperatures. In the vegetable garden use clean straw or hay up to 6 inches deep or a layer of compost 2 – 3 inches. Flowers, shrubs and trees can be mulched with a 3 inch layer of woodchips or shredded bark. Too thick of a layer in shady or moist spots can accommodate slugs and earwigs, however.

Scout for insect, disease and wildlife problems regularly so they can be treated early before too much damage has occurred. Find out what the key pests are for each of your plants and what to look for. Get help accurately identifying problems before attempting to treat them. In many cases, the damage may look worse than it really is or it may be too late to treat this year but you can plan for prevention for next year.

Call your County UW-Extension office for assistance in problem diagnosis. In Milwaukee County, call the UW-Extension Yard and Garden Line, Monday through Friday between 9:00 a.m. and noon at 1-414-290-2410. Or bring samples to the Walk-in Plant Diagnostic Clinics held on Wednesdays from 4:00 p.m. until 6:00 p.m. at the Milwaukee County UW-Extension office at 932 S. 60th Street in West Allis.

For more local gardening information and links to many other great gardening websites, visit the UW-Extension Hort Team site at wihort.uwex.edu.

Numbers in parenthesis after a garden calendar entry are for UW-Extension InfoSource messages. To use InfoSource in the metro Milwaukee area, call 414-290-2450 followed by a "1" and then the 3-digit topic number. In the rest of the state, call 1-800-441-4636.

 

First Week

Be vigilant in watching the leaves of your tomato plants for signs of leaf spot diseases. The most common, septoria and early blight, appear first on lower leaves and can be effectively controlled if leaves are removed as soon as leaf spots are seen. If it has gotten away from you, chemical control is also possible with a fungicide containing chlorothalonil.

To prevent bacterial wilt of squashes, melons, cucumbers, and gourds, apply rotenone, carbaryl or methoxychlor as a dust if either striped or spotted cucumber beetles are present. Dust late in the day after flowers have closed and bees are no longer active. Plants already infected with the wilt should be removed and destroyed immediately.

Squash vine borer is a difficult to control pest of vine crops, particularly summer squashes. Adults lay eggs for a three week period starting in late June. Cover lower section of stems with floating row cover or even aluminum foil to prevent egg laying. Look for and remove by hand any brown egg masses seen on the lower stems. Spraying carbaryl (Sevin) is more effective than using the dust formulation. If entrance holes and "sawdust" are seen, a wire can be inserted and threaded through the stem for some distance to kill developing larvae inside. Or slit stems lengthwise to find and destroy the caterpillar. Then bury slit stem section under some soil.

Renovate June-bearing strawberry plantings immediately after harvest. Control any weeds that have invaded and then mow over the top with the mower set high enough not to damage the crowns. Eliminate new plants between the rows by cultivating. Then sidedress with a 10-10-10 fertilizer. Lightly work it into the soil and water in.

Pinch back garden chrysanthemums one last time. Flower buds will form on new growth and be ready for fall display.

No further pruning should be done on trees or shrubs since the new growth this stimulates will not mature sufficiently before the cold days of winter are again upon us.


Likewise, woody plants should not be fertilized again until leaves begin to color and drop this fall. Fertilizing, like pruning, stimulates new growth.


Garden flowers, whether annuals or perennials, benefit from "deadheading" after flowering. By removing the spent flower heads, energy is used to produce more flowers or foliage and roots.

In general, flowering requires lots of energy so it can be quite helpful to fertilize flowering herbaceous plants once flowering begins. Fertilize once again before the end of the season.

If you will be watering your lawn all summer to prevent dormancy, fertilize lightly now.
 

Second Week

Watch for cabbage worm, corn borers, cutworms, potato leafhoppers, potato beetles, aphids, tarnished plantbugs, and thrips on many vegetable crops. Obtain a copy of UW-Extension publication A2088 to help you manage insects in the home vegetable garden. In Milwaukee County, call 290-2400 for ordering information.
preview UW-Extension pub A2088

Keep cole crops and potatoes covered with floating row cover to exclude cabbage worm and leafhoppers. Cole crops such as cauliflower, broccoli, and cabbage can be sprayed or dusted with Dipel (Bacillus thuringiensis), a biological control product. M-trak is a similar biological control for potato beetles.
(COLE CROPS)      (POTATOES)

Seeds can continue to be sown throughout July for late crops of beets, bush beans, carrots, chard, Chinese cabbage, cucumbers, kohlrabi, and corn. For summer planting, make the furrows and then moisten before sowing seeds. Cover with pre-moistened potting soil mix which will not be so likely to crust and crack.

Transplants of broccoli, cabbage, cauliflower, Chinese cabbage, collards, kale, kohlrabi, onion sets, and onion plants can be planted for fall crops. “Harden-off” plants before planting, plant early in the day, and shade with floating row cover fabric to prevent sunburn of tender young plants.

Keep tomato plants well mulched and evenly moist to reduce the incidence of blossom end rot and cracking.

Oak, elm, ash, and maples infected with one of the wilt diseases will begin to show typical symptoms as the summer heats up. Bring samples of branches that have recently wilted to your county UW-Extension office.
(LEAF WILT)      (DUTCH ELM)      (OAK WILT)

Begin looking for webs of fall webworm on woody plants. Control by cutting out branches wrapped in webbing where possible. Spraying with the botanical insecticide B.t. (Dipel, Thuricide, and others) is only effective on very young larvae.
 

Third Week

The final preventative spray of chlorpyrifos should be applied to the trunk and lower limbs of white-barked birches susceptible to bronze birch borer. Annual treatment includes two additional sprays on May 20 and June 15. Trees weakened by attacks leafminer are more at risk for bronze birch borer.
(LEAF MINER)      (BRONZE BIRCH BORER)

Allow asparagus to produce tops now. Fertilize the plantings with 10-10-10 fertilizer.

Summer raspberries should be coming in well now. Watch plantings closely for the many possible insect and disease problems. Harvest fruit often and thoroughly to reduce the number of picnic bugs competing with you for fruit. Viruses cause plants to be stunted and discolored, and fruits to crumble easily. See UW-Extension publication A1610 for pest descriptions and controls.
preview UW-Extension pub A1610

Ornamental kale, grown for its colorful foliage should be transplanted in mid-July. When planted earlier, this cole family member tends to bolt causing misshapen, cone-shaped plants.

Watch for yellowing and wilted leaves on cole crops such as broccoli, cauliflower, and cabbage. This may indicate black rot or club root, two serious diseases of these crops.

Divide iris plantings every 3 - 5 years to renovate plantings and clean-out borer infested plants.
(DIVIDING)      (WILT)

Fourth Week

Alpine currant shrubs infected with the anthracnose fungus will lose leaves and sometimes completely defoliate by mid-summer. Fallen leaves will be spotted with the fungus and should be diligently removed and destroyed to reduce the infection next year.

Honeysuckles susceptible to the common leaffolding aphid should be sprayed every 10 - 14 days with insecticidal soap. Pruning out infected stems every fall will reduce the population considerably but the prevalence of the insect means that others will probably fly in again. Since many species of honeysuckle are invasive especially in our natural areas, it might be best to consider replacing them with something else.