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

April, 2001

It's official. It's spring. Even people who don't garden notice it. Plants are popping up all over. On the trees, buds are swelling and about to burst. To think that within the next month, everything will be a fresh, bright green.

It seems to start with the lawn. Indeed, every homeowner feels the urge to do something to help it get growing and green again. Fertilization and weed control should wait, however.

Instead, begin by lightly raking out the meadow mouse trails and the gray and even pink snow mold. All are extremely common this year due to the lengthy snow cover from December until just recently. None are cause for concern, really. Just lightly rake those areas. As the grass begins its vigorous growth this spring, it will recover completely.

Fertilization and broadleaf weed control are more effective when done in the fall. Only if you missed last fall's fertilizer application should you lightly fertilize this spring and then only at half strength. The first fertilizer application of the year should be delayed until Memorial Day. 

Crabgrass should only be treated this month if it was a problem last summer. There may be more than usual because of the ample moisture we had all last year last. On the other hand, it may have had a harder time competing with our lawn grasses which grew so vigorously. Usually summer drought allows crabgrass to flourish. Reseeding these bare spots before crabgrass germinates may be all that's necessary. Do not sow new seed and then treat with a pre-emergent crabgrass weed killer. These products prevent seed germination in general, not specifically crabgrass.

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

Plant a pot of pansies and put them outside. Pansies are far from whimpy and can tolerate freezing temperatures and frost. If they are greenhouse grown, expose them to the cold a little more gradually.

Finish up your pruning chores this month. Pruned branches of spring flowering trees and shrubs like forsythia, pussywillow, apple, crabapple, cherry, plum, and flowering almond can be brought indoors to force into bloom.

Finish that plan for the vegetable garden and get your seeds. Consider planting colorful veggies amongst other landscape plants where there is plenty of space and full sun. For shadier spots, choose leafy vegetables. There's a wide assortment of lettuces, spinach and Swiss chard. Seeds can be sown directly into the garden about the third week of the month.

If you haven't already done so, sow seeds indoors of broccoli, early cabbage, cauliflower, celery, eggplant, and head lettuce. Peppers may be sown from seed indoors now, too.

Alyssum, verbena, calendula, celosia, coleus, dahlia, phlox and salvia can also be started from seed indoors.

Begin the process of hardening-off seedlings that will be transplanted outside later this month. This includes broccoli, cauliflower, cabbage, head lettuce, onions, and parsley. At first, place flats in a shaded place protected from the wind. Gradually increase their daily exposure to sun and wind. Bring them indoors each night until just a few days before planting.

Regularly check rose cones and other heavily mulched or protected plants, such as chrysanthemums. Temperatures can get quite high around these plants on sunny, warm days but it is still cold enough at night to damage new growth. Remove or vent cones only during the day and replace them before the sun goes down.

Open cold frames on sunny days but be sure to close them again before sundown.

Treat pine needle scale on mugo, Scot's, Austrian, white, and red pines with dormant oil. Dormant oil should be used before bud break but when temperatures will be above freezing for at least 8 hours.

Collect soil samples for testing. Sample vegetable gardens, flower gardens, lawns, and shrub beds separately. Each sample should consist of soil taken from 5 different spots within a particular area. Obtain soil sample mailers from your county UW-Extension office.

Second Week

Repair bare spots in the lawn. Work up the soil well in these areas incorporating some granular fertilizer, too. Sprinkle on a good seed mix bluegrass and fescue. Rake lightly to mix seed with soil. Tamp to assure seed-soil contact. Mulch lightly with straw. Keep well watered for 2 weeks until all the seed has germinated.

Longer days and higher light intensity means indoor plants will begin growing faster. Start fertilizing again using a half strength solution every other watering. Prune hard now to stimulate new, bushier growth.

Prune oak trees before April 15th. Trees pruned later are more likely to contract oak wilt disease from infected beetles feeding on the sap of fresh wounds.

If you have an oak tree that died of oak wilt last season, have it removed and the wood processed (burned, chipped, or at least the bark stripped) before April 15th.

Fertilize grapes, raspberries, and blueberries before growth resumes in the spring. See UW-Extension bulletin A2307 for specifies rates.
preview UWEX bulletin A2307

Cole crops, head lettuce, and parsley may be transplanted outdoors. Whether they have been "hardened off" or not, cover them with plastic milk jugs, glass jars, "walls o' water" or floating row cover fabric to protect them from the cold. Remove these on very warm days but replace them at night.

Third Week

Start tomatoes from seed indoors.

Sow seeds outdoors for the following crops: asparagus, beets, carrots, chard, kohlrabi, leaf lettuce, mustard, onion sets, parsnips, peas, potatoes, radish, spinach, and turnip.

Keep Easter lilies well watered. Cut out the bottom of the decorative foil and set the pot onto an inverted saucer or jar lid inside of another saucer to catch the drainage water. As buds continue to open, remove yellow pollen sacs from the stamens before the dusty pollen drops. It not only stains tablecloths and clothes but removal prolongs the flowers.

Prepare for apple tree pest control program. If insecticides and fungicides are going to be used, begin treatments as soon as buds begin to expand and grow. A few well-timed sprays early in the season may be all the chemical control necessary. Details are provided in UWEX publications A3565 "Growing Apples In Wisconsin" and A2179 "Apple Pest Management for Home Gardeners". 
     preview UWEX bulletin A3565     preview UWEX bulletin A2179

Begin pest control peach, plum, apricot and cherry. UWEX publication A2130 provides details.
preview UWEX bulletin A2130

Establish new plantings of grapes, strawberries, raspberries, asparagus, and rhubarb as soon as the ground can be worked. Proper preparation of the site including pre-plant weed control and the addition of organic matter and fertilizer will assure years of good growth for these perennial crops.

Fourth Week

Raspberry canes that will produce this year's crop should be pruned back by 1/4 before growth resumes. Last year's fruiting canes should have been cut down to the ground after harvest last year. Young canes that will bear this year should have been thinned, too. Leave only 3-5 canes per foot of row or 6-8 per hill.

Check upright junipers and red cedars for the brown galls of cedar-hawthorn/apple rust. They will be mingled with the leaves and resemble brown golf balls. Warm spring rains cause them to ooze orange gelatinous "horns" which spread spores to apple, crabapple, and hawthorn. Remove these galls before they erupt to limit the spread of spores.

Check birch leaves when half expanded for pale circular spots that indicate feeding of birch leaf miner. Early and well-timed chemical control is the key to minimizing the stress caused by this perennial birch pest.

Pre-emergent crabgrass control should be applied by May 1 before this year's seeds germinate. Apply only to those areas where crabgrass was a problem last year.

Celebrate Arbor Day on April 27th by planting a tree. Call the UW-Extension Dial-A-Garden-Tip that day for a special message about the history of Arbor Day and a few silly jokes and riddles about trees. Dial-A-Garden-Tip is available daily on InfoSource (290-2450), topic #791.