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

June, 2000

Spring gives way to summer in June. The danger of frost is past or at least the probability of frost is extremely low. 

The soil is still warming up so put off mulching vegetable crops like tomatoes, peppers, and eggplants until the middle of the month. Mulch placed over cool soil will keep soil cool longer.

The bugs of summer begin to make their presence known - both those that bug our plants and us. Garden during the heat of the day when mosquitoes are less pesky.

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.

Visit the UW-Extension Wisconsin gardening website at http://www.uwex.edu/ces/wihort/ . You'll find articles, resources and links to lots of other great garden-related sites.

First Week

June 1st is usually when its safe to plant even the tender flowering annuals and vegetables outside. Tomatoes with spindly stems can be buried in a trench up to the first set of true leaves. All other plants should be planted to the same depth as they were growing in the pot.

Don't fertilize tomatoes until the first fruit has set; too much nitrogen will cause leafy growth at the expense of flowers and fruit. Most other plants benefit from a starter fertilizer when transplanted.

June 1st is also when your first lawn fertilizer application should be made. If you fertilized earlier this spring, wait until Labor Day or Halloween to do it again. If you routinely water your lawn all summer long, another light application may be needed in July.

It is too late for broadleaf weed control products or combination weed 'n feeds. Summer's heat will cause the weed killer to vaporize and drift damaging other flowers & vegetables.

Houseplants really benefit from a summer vacation in a shady spot in the yard. Even those that prefer very bright light should be in the shade. Surprisingly, outdoor shade is still brighter than almost any spot indoors and the move back into the house in the fall will be less traumatic.

Prune, transplant and up-pot houseplants since they will be growing most vigorously now due to the longer days, higher light, and warmer temperatures. Fertilize monthly.

Most pruning chores for woody plants should be finished by now. It is now the time to prune pines to control size and make them bushier. The new growth, called the "candles", can be pinched back by up to 2/3rds once the new needles on them are slightly less than  half their full length.

Prune out and destroy webs of Eastern tent caterpillar found wrapped around branches of fruit trees including crabapples. The biological control sold as Dipel, Bactur, or Thuricide is only effective while they are still small. Soon they will move off the trees to pupate. Destroy these pale yellow, loosely constructed cocoons. In August look for shiny brown egg masses on tree branches. Prune them out or scrape them off

Examine honeylocust and ash foliage for plant bugs. Control with insecticidal soap sprays as needed.

There are many insect pests to watch for in the vegetable garden now. The following are pests in Wisconsin:

The flea beetle chews many small holes in the leaves of a wide range of vegetable crops especially young transplants of the cole crops. Cover with floating row cover to exclude these tiny, hopping bugs before they begin feeding. Hold down the edges with soil or stones to seal the cover.

Covering cole crop plants (broccoli, cauliflower, cabbage, and Brussels sprouts) with floating row cover will also exclude egg laying by the cabbage moths. This covering can be left in place day and night since it is permeable to light and moisture. It also "breaths" so that heat does not build-up underneath. Be sure to seal the lower edges with soil or stones. Allow ample room underneath for plant growth.

Potato leafhoppers are wedge-shaped and bright green insects that cause "hopperburn" on plant leaves beginning in early June. Spray once with carbaryl or malathion and cover the entire crop with row cover to prevent invasion.

Colorado potato beetle adults and larvae can be hand picked to remove or sprayed with M-Trak, a biological control product. Adults are yellow and black striped and the larvae are humpbacked and red. Look for them on the stem tips. They are present almost all season.

Striped and spotted cucumber beetles transmit a bacterial wilt to cucumbers, squashes, and melons. Adults and eggs can be hand picked throughout the season or preventative sprays or dusts with rotenone or carbaryl can be applied regularly. Leaves of infected plants wilt only during the day but the leaf stems remain erect. Eventually, the entire plant wilts and dies.

Preventative insect control for fruit bearing trees should have been started at petal fall. Continue every 10-14 days until autumn leaf drop. Preventative treatment for apple scab and rust diseases should have been started before bloom started. For crabapples, collecting and destroying fallen leaves all season combined with proper watering and a fall fertilizer application may be all that is really necessary since these diseases are not life threatening.

Second Week

Fertilize and renew June bearing strawberries after harvesting. Use 6 lbs. of 10-10-10 per 100 ft. of row. Plants form runners now and need good fertility for vigorous growth. Renovate by mowing the foliage and cultivating between the rows. UW-Extension publication A1597 has detailed instructions for strawberry culture.

Aphids of all types show up on a huge range of host plants as soon as the warm weather arrives. Look for them in newly unfurling foliage which may be curled downward and around aphid colonies. Sticky leaves are also a sign of their presence since they secrete "honeydew". Black sooty molds may also grow in this sticky substance but since they do not penetrate the leaves, they do little damage. Aphids, however, do. Spray leaves with a strong jet of water to dislodge some of them. Insecticidal soap is a low-toxicity product that provides pretty good control as long as the insects are wetted thoroughly with it. A second treatment to kill newly hatched eggs may be needed in 5 - 7 days.

Apply the second spray of Dursban or Cygon to trunks and main branches of stressed white barked birches to help prevent bronze birch borer. Repeat 3 weeks later.

Check spruce and arborvitae growing in hot, dry sites for spider mites. Tap a branch several times on a piece of white paper and then hold it very still for about 30 seconds. Mites will appear as tiny, black moving specks. 

Continue mowing around ripening foliage of spring flowering bulb plants growing in the lawn. For best flower bud development and vigorous growth next year, allow leaves to yellow completely before removing.

Fertilize bulbs and most perennial flowers now for good growth all season.

Third Week

Squash vine borer adults are 1" long orange and green day flying moths that are emerging from the soil now. They lay brown, button-shaped 1/16" eggs at the base of the vines of summer and winter squashes. Examine stems daily and remove eggs by hand to prevent burrowing of larvae as they hatch. Wrap lower 6 - 12" of stem with aluminum foil or floating row cover to prevent egg laying. Stem bases can be sprayed with carbaryl weekly for three weeks. The liquid seems to be more effective than dust.

Red sphere traps coated with Tanglefoot or STP Oil Treatment can be hung in apple trees now to control apple maggots. Use 1 trap per 100 apples expected. 

Fourth Week

Newly established plantings of raspberries can be fertilized now with 2 -3 lbs. of ammonium nitrate.

Fertilize roses after the first flush of blooms. Use one tablespoon of a complete, low nitrogen fertilizer per plant.

Pinch back chrysanthemums one last time now to promote fuller, denser growth. Flower buds will form on new growth for fall display.

Oak, elm, and maples with one of the wilt diseases will begin to show typical wilting symptoms as the summer heats up. Watch particularly the upper crown for branches with wilted leaves. Call your county UW-Extension to assist with diagnosis at the first signs of wilt.