Ask the Master Gardener: Planting a tree? Follow these steps to help it flourish for years

Dear Master Gardener: We want to plant some trees for Mother’s Day. Anything we need to know besides digging a hole and dropping them in?

Answer: Nature can be pretty forgiving and that might work sometimes, but to increase the odds of growing a healthy tree that will flourish for years, here are some things to do. Most importantly, buy a healthy tree that is meant for Zone 3. Young trees, besides being cheaper, will grow more vigorously and catch up to an older, more expensive tree in just a couple years. Pass up any bargains that have insects, broken limbs or have been badly pruned. Bare root trees are the easiest to transport and plant, as long as you can get them in the ground immediately — no waiting until you have time.

The University of Minnesota recommends box-cutting the root ball of container grown trees. Using a sharp spade or knife, slice down all four sides of the roots to form a square shape. This cuts through any roots that are circling around and will ultimately strangle your tree.

Another suggestion is to root wash. Using a hose, rinse off all the clay and potting soil until you can tease the roots apart, which can then be improved by pruning any that are going in circles or growing upwards. Dig your planting hole twice as wide but only deep enough so the root flare, where the first major roots grow horizontally, will be at or just above the surface. Spread the roots out like the spokes of a wheel in your planting hole and backfill with the soil you dug out. Add water as you go so there aren’t any air pockets. Never add anything extra to the hole — no matter what you’ve been told to buy or mix or line the bottom with. The tree has to learn to grow into whatever the surrounding soil is, so only put amendments like compost on top and let nature gradually add the nutrients.

Create a shallow basin to help hold moisture. Top this with a thick layer of wood chips to keep out weeds. Keep this mulch a couple inches away from the tree — no volcanoes piled up! Do not fertilize your tree for at least one year, and no pruning the crown at all except for broken branches. If your tree is really wobbly, stake loosely for just this summer. The tree has to be able to move a bit in order to signal the roots that they need to grow. Keep the tree well-watered all summer with slow, deep soakings. You won’t see much growth the first year, but once the roots are well established, the crown growth will take off in a year or two.

• Now is a good time to plant grass seed when temperatures are still cool and soil will retain needed moisture longer. Don’t spray for weeds where you planted. If you need to use a pre-emergence herbicide, use one that is specifically labeled for newly seeded lawns.
• 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 3-4 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.
• 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.
• Attract butterflies to your yard by planting the nectar-producing flowers they love such as purple coneflowers (Echinacea), Joe-Pye weed (Eutrochium), butterfly weed (Asclepias), beebalm (Monarda), catmint (Nepeta), Mexican sunflower (Tithonia), and zinnias. Be sure to avoid insecticides! As an aside, don’t bother putting up a butterfly house unless you are using it as garden art — butterflies won’t inhabit them.
• 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 repellent 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 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.