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Wisconsin Yard and Garden Tips

August, 2016

Plant Hardiness Zones Map | Last Spring Frost Map | First Fall Frost Map
UW Extension County Offices
By Sharon Morrisey, Consumer Horticulture Agent, Milwaukee County UW-Extension
Wisconsin Yard and Garden Tips is updated monthly by Milwaukee County UW-Extension. Applicability in northern Wisconsin counties may be delayed one to two weeks in spring, and advanced a like period in fall.

The dog days of summer are not even here and it seems we’ve had our share of hot weather already. One more month before the cool down starts. Even if we aren’t enjoying it, our plants certainly are.

Japanese beetles have been feeding on their favorite hosts which include roses, grapes and fruit trees along with lindens and birch. The female lays eggs in August and shows a distinct preference for lush, vigorous lawns to lay them in. If this month is dry, it could mean fewer grubs feeding on the roots this fall and next spring.

Spraying your most precious plants to protect them on a regular basis until the feeding frenzy ends by the end of this month will minimize the effects of that feeding which can weaken those hosts.

The Wisconsin State Fair is being held from August 4 – 14th in West Allis in Milwaukee County. Stop by the DNR’s Natural Resources Park on the fairgrounds to visit the UW-Extension Master Gardener volunteers at their display garden there. Learn about shade plants, butterfly and pollinator gardening, composting, rain barrels and rain gardens and some of the best native plants for sun and shade. There is even a hardy cactus and succulent bed for Wisconsin hardy cacti. The Extension Master Gardeners there can direct you to gardening resources that will help you throughout the growing season.

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.

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

Continue controlling stripped and spotted cucumber beetles which spread bacterial wilt to cucumbers, squashes, melons, and gourds. Weekly dusts or sprays of the organic insecticides containing spinosad or the synthetic carbaryl (Sevin) or permethrin (Eight) 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. Products containing the active ingredient spinosad are very effective and organic. The synthetic 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.

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 therefore wounds heal very slowly.

Second Week

Harvest vegetables such as tomatoes and melons regularly and frequently to avoid overripe fruit which attracts 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.

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 or floating row cover fabric 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 fuschia, 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. If there are signs of diseases, remove all leaf litter and spent plants to prevent the spread of spores.

Prepare for a Labor Day fertilizer application to the lawn. 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 on Memorial Day, Independence Day and Labor Day.

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.

For more information, contact Home Horticulture Agent Sharon Morrisey.

Plant Hardiness Zones Map | Last Spring Frost Map | First Fall Frost Map | UW Extension County Offices

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