Dear Master Gardener: I planted coral bells at the end of last summer and some barely came back. On a few you can see the crown with just a few tiny leaves coming from it. Are coral bells hardy in Minnesota?
Answer: It depends. There are many varieties that are hardy to zone 4, but only a few that are hardy or do well in zone 3. The problem with Heuchera (coral bell) is their tendency to rise out of the ground as they mature. If this happens, you should fill in extra soil or compost around the stem so the crown stays in contact with the soil or dig it up and replant it or divide it. Otherwise, it will be exposed to winter freezing and thawing, which could cause it to heave out of the ground, become dehydrated and die. The first year you plant Heuchera you should protect them with a 4-inch layer of winter mulch (leaves, pine needles, clean straw) after the ground has frozen. This will prevent the young plants from heaving during fluctuating winter temperatures. In following years if there is no snow by mid-December, apply a 4-inch layer of mulch at that time. Remove mulch in the spring as soon as the weather warms up to prevent crown rot.
Dear Master Gardener: Would wild ginger make a good groundcover for my woodland garden?
Answer: Yes! Wild (Canadian) ginger (Asarum canadense) is a great choice for a woodland garden. It is a Minnesota native plant found in moist woodlands and forests. It gets about 6-9 inches tall, grows best in part to full shade and spreads by rhizomes. The leaves are heart-shaped and densely covered in soft hairs on the underside. Canadian ginger flowers in the spring, but you have to look hard to find the flower. Each plant has a single, brownish-red flower that is jug-shaped and lies on the ground at the base of the plant between two leaves. As an aside, it is not related to the ginger we use for Asian cooking.
Dear Master Gardener: I visited a friend in northwestern Minnesota who has an interesting plant called dwarf indigobush. What can you tell me about it?
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Answer: Dwarf indigobush (Amorpha nana), also known as fragrant false indigo, is another Minnesota native plant that is definitely worth looking for! It is native to most of the western half of Minnesota and Crow Wing County. In its native habitat it is found in sunny upland prairies. This plant will not only add beauty to your landscape, but is excellent for pollinators. In early summer dense spike clusters of indigo-colored flowers with contrasting yellow stamens cover this deciduous shrub. Small green legume pod fruits persist into winter. This is a very short shrub, growing to a mature height of one to two feet. Dwarf indigobush blooms on old wood, so if you cut it back, it will not flower until the following growing season.
Dear Master Gardener: I don’t seem to have a problem with rabbits eating my flowers at my cabin in the Brainerd lakes area — probably due to the eagle population. However, my flower gardens in the Twin Cities seem to be a huge salad bar for the rabbits. Are there plants they don’t like, so I can replace the ones they’ve eaten with rabbit resistant ones?
Answer: Minnesota gardeners are reporting a high level of rabbit browsing in their gardens this summer. Like deer, rabbits will eat just about anything when they are hungry. You will notice signs of rabbit damage when you see your herbaceous plants, especially young ones, that have been nibbled down to the ground. If you have a prized perennial that you don’t want devoured by a rabbit you could put a cylinder of hardware cloth around the plant, but that isn’t very attractive. Repellents may deter them, or at least reduce the damage. Sprinkling dried bloodmeal on the soil around the plants may work, as rabbits do not like the smell of blood. It will have to be reapplied after it rains. Unfortunately, rabbits can build up a tolerance to repellents, so they eventually lose their effectiveness.
Some perennials and annuals often eaten by rabbits are: Aster, Coneflower, Gazania, Hosta, Asiatic and Oriental Lilies, Impatiens, Pansy, Phlox, Poppy, Rudbeckia, Sweet Peas, Tulip, and Verbena.
Plants with strong odors and/or dense hairs are typically avoided by rabbits. According to several sources there do seem to be some plants that rabbits avoid. Following is a list of some “rabbit-resistant” perennials: Aconitum, Ajuga, Allium, Artemisia, Aruncus, Astilbe, Baptisia, Bergenia, Bleeding Heart, Coreopsis, Daffodil, Daylily, Euphorbia, Fern, Foxglove, Geranium, Goat’s Beard, Hardy Chrysanthemum, Hollyhock, Iris, Lady’s Mantle, Lily of the Valley, Lobelia, Peony, Pulmonaria, Russian Sage, Salvia, Sedum, Tiarella, Virginia Bluebells, and Veronica. Rabbits seem to avoid some annuals such as Wax Begonia, Calendula, Cleome, Four O’Clocks, Marigolds, and Geraniums.
Dear Master Gardener: I heard crushed egg shells will keep slugs from eating hostas. Is it true?
Answer: This is a common recommendation. However, Professor Jeff Gillman, author of “The Truth About Garden Remedies,” conducted experiments to see if crushed egg shells would be effective slug fencing around plants. His wife made key lime pies with all the eggs, so they wouldn’t go to waste. Here are his results (p. 160): “Eggshells crushed to the size of baby aspirin and applied relatively deeply around your plants could inhibit the movement of slugs, but they won’t do anything to actually repel them. The depth necessary for the eggshells to deter slugs would require breaking quite a few eggs to protect the typical garden, certainly more than would normally be produced in a day of baking.” He estimated it would take a dozen eggs to create a 1/4 inch deep ring, 2 inches wide, around a small plant. Professor Gillman recommends using diatomaceous earth to repel slugs if you really want to repel them organically. And, make sure to get the diatomaceous earth sold for use on slugs, not for use in swimming pool filters (which is not effective on garden pests).
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.
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