Dear Master Gardener: How did hanging mistletoe in a doorway become a Christmas tradition? Where does it grow?

Answer: A popular American Christmas tradition is kissing under the mistletoe, although this year it may not be a good idea. Mistletoe has long been a symbol of love, peace and goodwill. In the 18th century, mistletoe became associated with Christmas from the tradition of hanging it in one’s home to bring good luck and peace to those within the house.

Related: Ask the Master Gardener: What to consider when picking out your Christmas tree

Mistletoe is a parasitic plant that lives off the tree it attaches itself to. According to the University of Illinois Extension, American mistletoe, which is native to the United States, can be found growing in the tops of hardwood trees from New Jersey to Florida and west to Texas and Illinois. It is hardy to zone 6. There are other species of mistletoe in western North America that are parasites on conifers. Most mistletoe sold during the holiday season is harvested in Oklahoma and Texas. Mistletoe is toxic and should not be ingested.

Dwarf mistletoe (which is not the type used for decoration) is found in Minnesota and most commonly attacks black spruce growing in the northern part of the state. White spruce is also highly susceptible to the parasite. Dwarf mistletoe can also attack white pine, red pine, jack pine, eastern larch, balsam fir, and Colorado blue spruce if they are near groups of infected spruce. Dwarf mistletoe can be identified by the clumps of small, weak branches called witches’ broom that arise from one point on a larger branch. If you have a conifer infected with dwarf mistletoe, you can prune it out to improve the look of the tree and reduce the spread of the infection. If more than 50% of the tree is infected, it should be removed.

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Related: Ask the Master Gardener: It’s rare but exciting for aloe vera plants to bloom indoors

Dear Master Gardener: I am working on a garden plan for next spring and will be building a pergola. I was thinking of covering it with wisteria. Does wisteria grow this far north?

Answer: Yes! Summer Cascade is a University of Minnesota wisteria that was bred from a hardy Kentucky variety and is hardy to zone 3. It’s a great choice for covering a pergola or arbor to create a shady retreat. In fact, it needs a heavy wood structure to support its weight. Once it is established, it can grow up to 10 feet in one summer. Pruning it several times throughout the growing season can restrain its size and promote more blooms. Summer Cascade blooms on new growth in June. In addition to the lovely, dark lavender, cascading bloom clusters, it also has interesting seed pods in late summer, providing multi-season interest. Wisteria performs best in full sun.

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December Gardening Tips

  • Check on dahlia, calla lily, and canna tubers. Discard tubers that have shriveled significantly, developed soft spots, smell funny, or show any signs of rotting.

  • Support Minnesota tree farms by buying your Christmas tree locally. They are a renewable crop usually produced on marginal agricultural land. As trees are harvested, others are planted for future sales. While they grow, evergreens reduce soil erosion and provide wildlife habitat.

  • Poinsettias are easy holiday plants to grow. Wrap it well so you get it home without suffering cold damage. If it came in foil, remove or poke holes in the bottom of the foil so the plant doesn’t sit in water. Keep your poinsettia in a bright location and water it thoroughly when the soil surface begins to dry.

  • To protect nearby plants, use sand or grit on icy sidewalks rather than deicing products. Damp sand, spread lightly will form a gritty nonslip surface which can be swept up in the spring. The more deicer you use over the winter, the more likely your lawn, perennials, and shrubs will be damaged.

  • If dust has built up on your houseplants, clean them off with lukewarm water. Don’t use leaf shine products, including “natural” ones such as milk or mayonnaise. They leave residue that attracts more dust. Check for insects, especially on the underside of leaves.

  • Share the garden season with others by framing your best flower and garden photos or making notecards and giving them as gifts.

  • Bloom-it-yourself amaryllis and paperwhite narcissus kits make great gifts for those who need some gardening cheer!

  • Monitor your trees and shrubs for damage done by deer and rabbits. Apply repellents and fencing to minimize damage.

  • With the long, dark days of winter upon us and being restricted to our homes due to COVID-19, adding a flowering plant (or two) to our home and giving them as gifts to cheer up our family and friends has never been so needed! Numerous research studies have shown that flowering plants, and plants in general, have positive psychological effects and reduce the negative effects of stress. A research study by the National Institute of Health used medical and psychological measurements to evaluate patients’ responses to flowers and plants in their rooms. The group with plants and flowers had significantly more positive physiologic responses (lower blood pressure, lower ratings of pain, anxiety, and fatigue) and a more positive attitude toward their room and staff, than those in control rooms. Here are some great choices: cyclamen, orchid, poinsettia, kalanchoe, Christmas cactus, anthurium, clivia, and zebra plant.

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.