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

April, 2007

Just a couple of weeks ago it was hard to believe the snow melt and the world turn green again. But they have.

Warm weather lures people into their yards with renewed resolve to do everything right this year. Put off a thorough clean-up of flower beds since the leftover dried leaves and stems actually provide protection for the newly emerging shoots on those frosty nights we are still likely to get in April.

The lawn will benefit from core aerating once it starts growing. Rake out the areas where meadow mice tunneled under the snow. Weed seed germination preventers can be applied when the forsythias bloom. If you didn’t fertilize last October, a light application now can make up for it. Otherwise, wait until Memorial Day. For a Wisconsin Lawn Care Calendar, go to the UW-Extension Horticulture Team website at wihort.uwex.edu and look for the link to the Wisconsin Garden Facts publications.

There are still two months before tender annual flowers and vegetables can safely be planted outdoors. Some seeds can be sown directly into the garden this month and others should be started under lights indoors.

The numbers following some of the calendar entries can be used to access InfoSource factsheets from the internet at infosource.uwex.edu.

UWEX publications on these and many other gardening topics can be obtained from the website at learningstore.uwex.edu.
 

First Week

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.

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.

Plant a pot of pansies and put them outside. Pansies can tolerate frost, freezing temperatures and even some snow (heaven forbid). If they are greenhouse grown, expose them to the cold a little at a time.

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.


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.
 

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 of 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. UW-Extension bulletin #A2307 specifies rates.

Cole crops, head lettuce, and parsley may be transplanted outdoors.
 

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.

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".


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

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

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.

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".


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

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.