Ask the Master Gardener: Good shrubs for creating a living fence

Dear Master Gardener: What can I plant to form a “living fence”? I have a dream of blocking out the neighbors with a mixed species hedge that would be good habitat for wildlife and pollinators.

Answer: Shrubs can be planted closely to form a hedge or “living fence.” Here are a few recommendations to match your wish list (tall enough to block neighbors and good wildlife and pollinator habitat.)

• Nannyberry (Viburnum lentago) is a native species that provides year-round interest. It sports white flowers in late spring, has red-purple foliage in summer, and bluish-red, edible berries in the fall that have a sweet, date-like flavor when ripe. This is a large upright shrub that reaches 15-20 feet tall at maturity, making it a great choice for a tall privacy screen. It grows well in part shade to full sun. Because it is a host plant for numerous moth caterpillars it is considered a top wildlife plant for nesting birds. If the birds do not get to the fruit first, the berries can be used to make jams and jellies.
• Highbush cranberry (Viburnum trilobum) is another native shrub that is popular to use as a screening hedge. It blooms in spring with white clusters of florets. The dark green foliage turns purplish-red in the fall with drooping clusters of bright red, edible berries that persist into winter. Cedar waxwings and other birds love the berries! If they leave any for you, the tart berries make excellent jams and jellies. Highbush cranberry grows well in part shade to full sun, and needs consistent moisture. At maturity this hardy shrub reaches 8-12 feet in height and about 10 feet wide. For a solid screen, plant the shrubs about four feet apart.
• Ninebark (Physocarpus opulifolius) is another Minnesota native, hardy to zone 2, and another great shrub to use for a screening hedge. It reaches 10 feet in height and width at maturity. Ninebark blooms in late spring with clusters of nectar-rich white flowers that attract many beneficial insects, including butterflies. Diabolo is a cultivar with deep purple foliage that contrasts beautifully with the cream-colored flowers. It grows best in full sun, as the foliage can turn green in partial shade or high heat. It gets 8-10 feet in height and width at maturity.
• Another native shrub often used for screening is red twig dogwood (Cornus sericea). It readily grows to 8 feet tall and the cultivar Baileyi gets 10 feet tall. It has multi-season interest with creamy white flower clusters in late spring, white berries in late summer, beautiful fall color in shades of yellow and orange to dark red (if it receives full sun), and beautiful red stems that stand out in the winter landscape. Red twig dogwood is a good source of nectar and pollen for bees and butterflies and the berries are enjoyed by birds.

• Now is a good time to plant grass seed when temperatures are still cool and soil will retain needed moisture longer. For good results, rough up the soil first. Do not spray for weeds where you planted. If you need to use a pre-emergent herbicide, use one that is specifically labeled for newly seeded lawns.
• If you have an ornamental crabapple tree that is prone to apple scab (leaves that develop dark spots, turn yellow, then fall off early) begin a fungicide spray program before its flower buds open. Check the fungicide label for the recommended spray interval — usually seven to 10 days after spraying you will need to spray again. Typically, two well-timed fungicide applications in spring will protect ornamental crabapples from apple scab.
• Prune forsythia, azaleas, lilacs, and other spring flowering shrubs immediately after they are done blooming.
• Divide any perennials that need it. Spring is the best time to divide summer and fall blooming perennials. Fall is the best time to divide spring and early summer blooming perennials.
• Perennials need very little fertilizer. Top dress established plantings with several inches of compost every three-four years.
• Wait to plant warm-season annuals (such as begonias, coleus, and impatiens) until both the air and the soil are warm — usually the last week of May or first week of June. Cool-season flowers such as snapdragons, alyssum, pansies, and dianthus can be planted earlier in the month.
• Annuals such as bachelor’s buttons, California poppies, cosmos, zinnias, and marigolds grow rapidly from seed and can be sown directly into the garden in May.
• Acclimate plants to the outdoors by setting them in shaded, protected areas during the day and bringing them indoors at night. Avoid direct sunlight until plants are outdoors full time.
• Pull weeds as soon as you discover them. Thistle, dandelions and quack grass are some of the first to appear. Removing weeds before they set seed saves pulling hundreds more next year.
• Peas, leaf lettuce, spinach, and radish seeds can be sown directly in the garden now. Transplant onions and members of the cabbage family (cabbage, cauliflower, and broccoli) while the soil is still cool. Wait until the last week of May or first week of June when both the soil and air temperatures are warm before planting tomatoes, peppers, and eggplants.
• When spring-flowering bulbs are done blooming, cut off the faded flowers to prevent seed production.  Allow the foliage to yellow and begin to shrivel before cutting it down.
• Attract butterflies to your yard by planting the nectar-producing flowers they love such as purple coneflower (Echinacea), Joe-Pye weed, liatris, butterfly weed (Asclepias), beebalm (Monarda), catmint (Nepeta), Mexican sunflower (Tithonia), and zinnias. Be sure to avoid insecticides! Don’t bother putting up a butterfly house unless you are using it as garden art — butterflies won’t inhabit them. They sleep high up in trees, nestled in the safety of leaves.
• Add some edible shrubs to your landscape by planting Minnesota-hardy blueberries or Canadian-bred honeyberries. Blueberries need acidic soil (pH 4.0-5.0) to thrive, whereas honeyberries thrive in a wide range of soil pH (5.0-8.0). Both blueberries and honeyberries need a different cultivar for cross-pollination. New bushes can be planted in May.
• Start the gardening season with a healthy garden. Rake and compost old leaves and fallen fruit. Cut back perennials and ornamental grasses. Wash and sanitize tools, pots, cages, and stakes. Top off containers with fresh potting soil. Add mulch as needed to garden beds and paths. 
• Start a compost pile or bin. Not only does finished compost add nutrients and texture to garden beds, but the pile or bin becomes a convenient place to throw leaves, small twigs, weeds, and kitchen fruit and vegetable waste.
• Begin deer and rabbit repellant use and install fences and other physical restraints now before those critters put you on their regular meal run.

You may get your garden questions answered by calling the Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at umnmastergardener@gmail.com and I will answer you in the column if space allows.

University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.

You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at umnmastergardener@gmail.com and I will answer you in the column if space allows.

University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.