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

August, 2000

Plants have really been enjoying this abnormally cool summer and show it by growing lush and lovely. We gardeners have appreciated Mother Nature's help with the watering which has been helpful where it hasn't been excessive.

While the wet season has enhanced plant growth, it has also favored certain fungal leaf spot diseases. Tomatoes have more than the usual problems with septoria and early blight. Anthracnose is typical on ash trees and sycamores but this year it is also being seen on oak, maples, elms and even many herbaceous perennial garden flowers. 

Apple scab is by far the worst of the fungal leaf spot diseases. Spotted, yellowed, dry leaves have been falling from area crabapples,leaving trees almost leafless and very unsightly. It happened even earlier than usual this year. Scab is not deadly but it is certainly hard on tree health. Continue raking and removing or mowing and bagging the leaves as they fall. Do not wait until all the leaves have fallen and become brittle since they will crumble when raked and the remaining pieces will be there to provide spores for next year's infestation. Do not compost collected leaves but bury them, burn them or haul them away. Over the winter, give some serious thought to replacing the existing susceptible tree with a scab resistant variety like Prairifire, Donald Wyman, Louisa, or Indian Summer.

Throughout August and September you can continue to bring questions and plant problems to the Plant Doctor Clinics at Boerner Botanical Gardens. held weekly from May through September on Tuesdays from 2:00 until 6:00 p.m. There is a $3.50 charge to enter the gardens.

Again in this month's calendar, the UWEX Infosource documents are available for further discussion on a topic.  Just follow the link under the paragraph of that topic.

First Week

The last date to sow sweet corn for the year is August 1st.

For late crops of beets, bush beans, carrots, Chinese cabbage, cucumbers, kohlrabi, and onion sets, continue sowing seeds until August 15th. Peas and collards can be seeded again now, too.

Transplants can still be planted of broccoli, early cabbage, cauliflower, collards, kale and onions. Exclude imported cabbage worms from late plantings of these cole crops by covering them with floating row cover. Be sure to seal the edges thoroughly with soil.  

Aphids can continue to show up all season long. Dislodge with a strong blast of water or use insecticidal soap (not dishsoap) when first noticed.

Continue controlling stripped and spotted cucumber beetles which spread bacterial wilt to squashes, melons, and gourds. Weekly dusts or sprays of rotenone, carbaryl, or methoxychlor are effective but only if insects are present. Apply late in the day after flowers close and bees are not
present. Remove infected, wilted plants immediately.

Colorado potato beetle adults are back for a second generation. Since these distinctive, globular, yellow and black striped insects are so easily seen they can either be removed by hand or sprayed. A specific strain of B.t. called M-trak is effective against these beetles while they are still young. The insecticide carbaryl (Sevin) can also be used.

After the last raspberry harvest for the year, prepare for next year while also avoiding diseases by pruning out old flowering canes leaving only 3-4 young canes per foot of row. Wait until spring to prune back shoot tips.

Watch for the appearance of fall webworm webs on limbs of trees and shrubs. Cut out the tents or spray while the larvae inside are still young using the biological insecticide B.t. (Bacillus thuringiensis) sold as Dipel, Thuricide, or Bactur.

Avoid pruning trees and shrubs since doing so this late in the season can stimulate new growth that will not harden off in time for the cold winter weather ahead. Delay pruning until the end of the dormant season early next spring. Late in the season when trees and shrubs are going dormant, wounds heal very slowly. Tender wound tissue can also be killed by freezing temperatures.

Second Week

Harvest vegetables such as tomatoes and melons regularly and frequently to avoid
overripe fruit being present to attract picnic beetles.

Harvest onions and garlic as the tops dry and fall over. Braid garlic tops and hang in a cool, dry place. Cut onion tops back to 1" and dry thoroughly before storing. Use any damaged produce immediately. 

Fall bearing raspberries will begin ripening. Pick fruit as soon as ripe since overripe fruit attracts picnic beetles which will seriously damage fruit.

Make the second application of fertilizer on new plantings of June bearing strawberries. Apply 3 lbs. of 10-10-10 per 100 feet of row.

Share the bounty of your harvest with others by donating excess produce to a local agency that provides food to people in need. Contact Second Harvest at 414-931-7400 to find a location near your home to donate fresh produce.

This is a good time to order and plant spring flowering bulbs for next year's early flower display. Plan for different flowering times to extend the season. As with most flowers, they are best displayed in masses of all one type and color rather than in mixtures which can be busy and garish. 

Third Week

From now until September 20th is the ideal time to seed or sod new lawns or to repair diseased or damaged areas of your yard. Prepare areas with an application of the herbicide glyphosate 10 days before seeding or sodding. Rototill the area to a depth of 6-8". Work in extra organic matter and fertilizer. Level and rake smooth. Rake seeded areas lightly to bury seed about 1/8 inch. Tamp to assure good seed to soil contact. Cover newly seeded areas with a very light layer of straw to help retain moisture. Do not allow to dry out until all grass has emerged - about 15 days. Mow as soon as the new grass is 3 - 31/2 inches tall. 

Seeds can again be sown for a late crop of leaf lettuce, mustard greens, Swiss chard and spinach.

If you haven't already done so, divide irises now before their second flush of root growth which will occur during fall's cool, moist weather. Examine rhizomes for borer tunnels and soft rot. Destroy all infected plants. Replant by barely covering the small sections of rhizome each with a fan of leaves and some roots. Cut leaves back by 2/3's.

If you want flowering plants indoors this winter of fushia, wax begonia, impatiens, geraniums, and coleus, root cuttings now in vermiculite or perlite. Use rooting hormone powder on cut stem ends. Keep flats or pots in a calm, shady spot outdoors until mid-September.

Fourth Week

In the flower garden, continue deadheading which will allow plants to use energy reserves for a final flower display. Remove all leaf litter and spent plants to prevent the spread of disease. 

Prepare for a Labor Day fertilizer application to the lawn unless you will be doing a weed n' feed treatment later in September. Mid-September is the only time of year when weed and feed products are actually timed right for both the weed control and the fertilization. If you do three applications of fertilizer per year, they should be at Halloween, Memorial Day and Labor Day. Use a slow release product for the late season application. 

Make plans for fall broadleaf weed control in the lawn since fall is when chemical control is most effective. Target specific weeds and treat only the areas where they grow. 

Late season problems on deciduous plants should be of lesser concern than those that appeared earlier in the season since leaves will soon change color and drop anyway. Diseased leaves should be removed promptly to minimize pest problems next year.

When the leaves begin to color and fall, its time to fertilize trees and shrubs but only if they are showing slowed growth, are pale in color, or have been stressed either by pests or difficult environmental conditions.