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As the Master Gardener: Don't mouse around with rodent tree damage

A girdled apple tree, damaged by mice or voles, which eat the bark. Photo by Jennifer Knutson

Dear Master Gardener: We have nine apple trees and six of them have no bark left on the bottom 12 inches of the trunks. We have had the trees for two to three years and this is the first time we've seen damage. I'm pretty sure it is mouse damage. Will they survive?

Answer: Mice and voles feed on apple trees of all ages by chewing and peeling bark from tree trunks and roots near the soil surface. When there are lots of rodents in the fall and then deep snow, like this year, we often see significant harm to trees. If there is partial damage to the trunk, the trees may survive, but will be severely weakened. If the trees have been completely girdled, they may leaf out, but will most likely die later in the season since the tree can no longer properly transport water up to the canopy.

You can protect your remaining trees next fall by keeping any grassy areas around your trees mowed short. Try to keep any grass, weeds and/or mulch away from the trunk of your trees. Protect tree trunks by placing cylinders of ¼-inch mesh hardware cloth around the trunk of each tree.

Rabbits will also damage or kill trees by girdling them. For rabbits, the cylinder should reach 18-24 inches above the anticipated snow line.

Dear Master Gardener: I purchased a beautiful trellis and would like to plant a Clematis. When can I plant it and what should I do to ensure success? Which ones perform best in our area?

Answer: A potted Clematis can be planted in the spring after there is no danger of frost. If the soil in the pot is dry, soak it and let it drain overnight. Choose your planting site carefully because Clematis do not like to be moved. There is an old adage, "Clematis like their heads in the sun and their feet in the shade," so find a spot where the root zone will stay relatively cool, or shaded by other plants. Dig a hole deep and wide and add a lot of organic matter to the soil. Position the crown of the plant (where the roots meet the stem) 2 to 3 inches below the soil surface. Backfill the hole and water deeply to settle the roots. The root system will spread throughout the entire prepared area and beyond. A newly purchased plant usually does not need fertilizer as it will often have received plenty during cultivation. Add three inches of mulch around the base of the plant being careful not to have it up against the crown and stem. Finally, add your permanent plant support next to the plant.

There are many cultivars that do well in the Brainerd lakes area. Any Clematis in the Jackmanii Group are easy to grow, vigorous and ideally suited to our cold climate (40 degrees below zero hardiness). Those that are in the Texensis Group (Duchess of Albany—a two-tone pink) or Viticella Group (Betty Corning—lavender, Etoile Violette—deep purple, Huldine—white) do very well here. Named varieties that are also highly recommended for our area include: Blue Angel (pale blue), Comtesse de Bouchaud (rose pink), Durandii (periwinkle blue), and Red Cardinal (red). When in doubt, check the plant label to make sure it is hardy to zone 3.

Dear Master Gardener: I planted two blueberry bushes a few years ago, but haven't been getting any blueberries. What should I do?

Answer: Blueberries require acidic soil and full sun. The optimum soil pH for blueberries is 4.0 to 5.0. If your plant has light green or red leaves in the summer or not much shoot growth, it is likely that the soil pH is not in that optimum range or nitrogen is needed, so use an organic acid fertilizer. At least two varieties should be planted to ensure successful pollination. Bees and other native insects pollinate blueberries, so the more insects you see around your plants, the more fruit you will get.

Blueberry plants grow slowly and do not reach maturity for eight to ten years. The plants won't produce much fruit the first two to three years, so if your soil pH is in the optimum range, the plants are in full sun and you have two varieties, patience may be all you need.

University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. All information given in this column is based on university research. To ask a question, call the Master Gardener Help Line at 218-454-GROW (4769) and leave a recorded message. A Master Gardener will return your call.