Spring is in the air
Dear Master Gardener:
Is spring the best time to prune trees and shrubs?
Pruning at the correct time is important for the health of your trees and shrubs. Pruning during the late dormant season (late winter, before spring growth begins) is best for most trees. Oaks should not be pruned in April, May, or June. Apple trees, including crabapples should be pruned any time between February and early April because spring or summer pruning will increase the chance for infections and/or the spread of fireblight. Trees that have free-flowing sap, such as maples, butternut, walnut, birch, ironwood, and blue beech can be pruned when their leaves are fully expanded in late spring or early summer to prevent bleeding. Remember not to remove more than ¼ of the live foliage.
Trees and shrubs that bloom early, such as azalea, chokeberry, chokecherry, forsythia lilac, and early-blooming spirea, should be pruned right after they have finished blooming. Shrubs, such as barberry, burning bush, dogwood, honeysuckle, ninebark, and other bushes grown more for their foliage than flowers, should be pruned in spring before growth begins. Shrubs that bloom on new growth may be pruned in spring before growth begins. Shrub roses should be pruned back to live wood. Late-blooming spireas and smooth hydrangeas (snowball) should be pruned to the first pair of buds above the ground. Potentilla will bloom best if one-third of the oldest stems are removed to the ground each year before growth starts.
Dear Master Gardener:
What flowering shrubs do you recommend for our northern climate?
There are many beautiful, flowering shrubs from which to choose for our Zone 3 climate. The azaleas that are hardy in this area were developed by the University of Minnesota and are the ‘Northern Lights’ series. They range in size and color from 3 feet (‘Orchid Lights’) to 8 feet (‘Pink Lights’ and ‘Rosy Lights’). Rhododendron ‘P.J.M.’ is evergreen with lavender-pink flowers and is proving to be hardy to -35 degrees F.
The American Cranberry Bush Viburnum grows to be 7-12 feet tall and has large, flat-topped clusters of white flowers that bloom in June. Arrowwood (Viburnum dentatum) grows to 7-10 feet and has white clusters of flowers. Another flowering Viburnum is the Nannyberry, which gets 15 feet tall and blooms in late May with clusters of ivory flowers. The Pagoda Dogwood is a beautiful, 15 foot, native shrub with horizontally spreading branches that produce small, creamy white flowers in June.
Hydrangeas are deciduous shrubs that grow better in semi-shade rather than full sun. Annabelle Hydrangea (Hydrangea arborescens) is hardy here and has very showy flowers that start out green and then turn white. Peegee Hydrangea (Hydrangea panicualta ‘Grandiflora’) has white, conical-shaped flowers, which turn a pinkish hue as they age and bloom in August and September.
There are a variety of lilacs that range in size and color that are hardy here. To get an abundance of flowers, lilacs need to be planted in full sun. Potentilla, also known as cinquefoil, blooms throughout the growing season starting in June and come in yellow, white, and pink. Anthony Waterer Spirea has bright rosy lavender flowers and Vanhoutte Spirea is an arching shrub that has white blooms. Weigela is a flowering shrub that comes in red, white or pink and is hardy to Zone 4, but many in the area are having good luck with growing it.
Crow Wing County Master Gardeners are trained and certified volunteers for the University of Minnesota Extension Service. All information given in this column is based on research and information provided by the University. To ask a question, call the Master Gardener Help Line at 218-824-1000, extension 4040 and leave a recorded message. A Master Gardener will return your call.