Calendar & Tips

Garden Calendar for July 2008

By Sharon Morrisey
Consumer Horticulture Agent

Abnormal is what we can call this season so far.  Cool temperatures earlier delayed development of plants and pests.  Now, excessive moisture is complicating things, too.  Saturated soils and flooding will lead to root rot and death depending on the plants affected and the length of time the soil was waterlogged.  Some species suffer after only a few hours while others that are more adapted to floodplain habitats can tolerate 3 – 5 months of standing water.  The stress of severely wet soil can make plants more susceptible to other insects or diseases that will ultimately be their cause of death.  This is even more likely if the plant was stressed by other factors before the flooding.

Symptoms can range from minor to extreme and may occur almost immediately or not show up until a year from now or more.

True vigilance is needed to watch for signs and symptoms of problems.  The key is to accurately identify the problem and decide on treatment early on.  UW-Extension can help.  Each county UW-Extension office in southeastern Wisconsin operates a Horticulture Help Line.  Call to talk to UW-Extension staff and volunteers who can discuss your plant problems and provide solutions. The new UW-Extension Horticulture Center located at Boerner Botanical Gardens is open Monday through Friday from 10:00 – 2:00 and Thursday evenings from 3:00 – 6:00 pm.  It is located on the lower level of the Education and Visitor Center at the garden in Whitnall Park in Hales Corners.

Wisconsin gardeners have a unique learning opportunity this summer.  Everyone is welcome to attend the Midwest Master Gardener Conference July 16 – 19 at the Wyndham Milwaukee Airport Conference Center.  Gardening through the Continuum of Life is the focus for over 30 workshops and keynote speakers including Victory Garden host Michael Weishan and Melinda Myers of The Great Lakes Gardener, also on public television.  Six fantastic private gardens including a “rosarium” of a renowned rose hybridizer are options for the conference tours. Register for the whole conference or just the tours at http://sewmg.encumpus.com/ .

First Week

Watch 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. (478)

To prevent bacterial wilt of squashes, melons, cucumbers, and gourds, apply rotenone or carbaryl (Sevin) 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. (349)

Squash vine borer is a difficult to control pest of vine crops, particularly summer and winter 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. (852)

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.

Trees and shrubs should not be fertilized again until leaves begin to color and drop this fall.  Fertilizing, like pruning, stimulates new growth. (555)

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.  Go to learningstore.uwex.edu.

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. (348 & 493)

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. (465)

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. (477)

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. (335, 432 & 833)

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 very effective on very young larvae.

Third Week

Fertilize asparagus plantings with 10-10-10 fertilizer now. (480)

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, yellow jackets and multi-colored asian ladybeetles 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.

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. (489)

Divide iris plantings every 3 - 5 years to renovate plantings and clean-out bore infested plants. (449 & 450)

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.  (840)