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Wisconsin Yard and Garden Tips

April, 2014

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.

This time last year we were talking about how long and cold the winter had been but spring was already here. Boerner Botanical Gardens reports that some Winter Aconite and Snowdrops have already bloomed. My guess is that these plants are in a very protected spot near a south facing wall that warms them.

Snow is predicted for the night Iím writing this. The ground is solid ice, too, but Iím still looking for buds on my Lenten Rose and the Bloodroot to start pushing leaves through the matted down groundcover. Wishful thinking never hurt.

On the nicer days, just about all you can do is pick up sticks and some light lawn raking. Snow mold is already showing where the snow banks linger. Raking breaks it up and helps the area dry out. Meadow mouse trails etched under the snow are exposed and can be raked to fluff them up. Both of these are just ways to get outside and enjoy the yard. Neither problem does any real damage and nothing really needs to be done.

Things you do not need to do right away include cutting back perennials and cleaning out all of last seasonís debris. These provide protection for the tender young shoots that will soon emerge. Without a little protection around them, the inevitable spring frosts can damage them and cause a setback.

You also should not work the soil in any bed or garden until it has dried out enough to pass the crumble test. Take a handful, squeeze it into a ball and then poke it gently. If it doesnít crumble, walk away from that bed and find something else to do.

There are plenty of other things to do as you will see by the number of entries in this monthís calendar.

The UW-Extension Horticulture Team website at contains research based information for you to use to make good decisions about caring for your lawn and garden. There are also UW-Extension publications on many of the topics in the calendar and much more at .

First Week

Finish up your pruning chores this month before the buds begin to open. 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 they have not already done so outdoors.

Prune oak trees before April 15th. Oaks 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. Wait until the ground has thawed so it does not runoff with rain water and melting.

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. Wait a week or so for the tomatoes.

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

Plant a pot of pansies and put it outside. Pansies can tolerate frost, freezing temperatures and even some snow. If they have been held in a greenhouse until you buy them, expose them to the cold a little at a time.

Regularly check rose cones and other heavily mulched or protected plants, such as chrysanthemums and strawberries. 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 while still remaining under 80 degrees.

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 or do it on-line at .

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 or fescue or both. Rake lightly to mix seed with soil. Tamp to assure seed-soil contact. Mulch lightly with straw. Keep well watered for 2 to 3 weeks until all the seed has germinated. It takes bluegrass 3 weeks to germinate.

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.

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

Begin the process of hardening-off vegetable and flower 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. If the weather remains unseasonably mild, they can really benefit from this pre-plant procedure. Resist the urge to plant them out in the garden too soon. It should not be before the average last frost date in your area.

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

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 but if not, do it now. 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.

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 so it is not drawn back up into the soil. 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. You can plant them outside in a protected spot near a building around mid-May.

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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