University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article


SPRAYING DORMANT OIL AND OTHER APRIL GARDENING TIPS

 
Charlie Nardozzi, Senior Horticulturist
National Gardening Association, and
Dr. Leonard Perry, Extension Professor
University of Vermont
 
Spraying dormant oil, sowing early crops, and preventing weed germination in lawns, are some of the gardening tips for this month.
           
If scale or aphids have been a problem on trees and shrubs, get the dormant oil spray ready for a day above 40 degrees with no wind. Coat the branches, and repeat if directed on the label. Early spring, when young scales are in the crawler stage, is the best time to control these pests.
           
The first crops that can be sown in the ground once the soil has dried out enough are beets, carrots, lettuce, parsley, peas, radishes, spinach, and Swiss chard. Plan to make successive sowings to prolong the harvest.
           
Once the soil reaches 45 degrees and is dried out enough to dig, it's time to plant peas. Choose a location in full sun and orient the rows north-south to take full advantage of the sunlight. Turn over the soil with a garden fork, or rototill if it's a new bed. Soak the seeds for a few hours or overnight (no longer or they may rot), and dust the seeds with an inoculant of nitrogen-fixing bacteria to help the roots take in more nitrogen. You can find this inoculant online or at many full service garden centers.
           
Set up your pea trellis first, then plant the seeds 1 to 2 inches deep. Cultivate very shallowly because the roots grow close to the surface; better yet, pull the weeds by hand so you don't accidentally cut off a plant.
           
Moving a woody plant before it begins new spring growth causes less stress on the plant, so try to do this type of transplanting as soon as the soil is workable. The larger the plant, the more the timing matters.
           
Before annual crabgrass and other lawn weeds germinate this spring, spread corn gluten pre-emergent herbicide/fertilizer with a lawn spreader. The corn gluten suppresses seed germination and also provides nutrients to the grass. Use the blooming time of forsythia to signal that it's time to spread the crabgrass control.
           
If you have dead spots in the lawn, plan to patch them before the summer heat. Loosen the soil and work in some good quality compost, sprinkle grass seed, rake lightly, and tamp to assure good seed-to-soil contact. Mulch with a thin layer of straw. Water as needed to keep the soil evenly moist until the grass sprouts.
           
Woody perennials differ in the way they should be cut back in spring. If butterfly bush has died to the ground, cut the dead stems to the ground. Otherwise just shorten them by about one-third. Cut back Russian sage, rue, and artemisias to about 8 to 12 inches from the ground. Don't prune lavender until new growth appears and then just shorten the stems by about one-third. Heather should be lightly pruned to remove the old flowers and the tips of the shoots, but don't cut back to brown wood, stay in the green. Prune spring-flowering shrubs such as forsythia and lilac right after they bloom.
                

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