Dear Master Gardener: My sister, who lives in the Twin Cities area, has jumping worms and says it’s her worst nightmare. Her soil looks like coffee grounds and plants are suffering. Because of her problem I am wondering if I should still add mulch, compost or wood chips to my garden beds. Or, does that just feed the jumping worms?

Answer: Jumping worms, an invasive species, change the soil texture so it appears like coffee grounds, strip the soil of nutrients, and can severely stunt or kill plants. Research on jumping worms is limited at this time. According to the University of Minnesota, “Jumping worms are great at digesting cellulose, a key component of wood chips. This allows them to survive and spread in mulch. It is unclear if adding mulch, compost or wood chips to the landscape improves the environment for jumping worms. It is clear these activities do not limit jumping worms. More research is needed to establish recommendations for best landscape practices when jumping worms are present.” At present there is no treatment to get rid of jumping worms. Watch for them in your yard and report them to the DNR if you find any.

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Dear Master Gardener: Three years ago, I planted 50 each of 18-inch bare root stock of Elderberry & Aronia. I used planting tubes to protect them from the deer. Many have grown to the top of the 3-foot tubes. Should I leave them in the tubes longer or would this be a good time to remove them? I put 3 inches of wood chips around the plants but crabgrass has grown up through the wood chips. Should I use an herbicide or just mow it? If I would use an herbicide, which one do you recommend and how should it be applied? Do you recommend fertilizer?

Answer: According to the Minnesota DNR Forestry Department and Soil & Water Conservation District, as a general rule, you want the tube on the tallest part of the tree/shrub to protect the new growth, so you could move the tube up. Otherwise, the forester I spoke with at the DNR says to go ahead and take them off since they are growing past the protective tube. In addition, if you wait too long to remove them, the lateral branches start to poke through and could get caught and tear off, which would damage the plant. SWCD recommends hand pulling the crabgrass or mowing it. If you do want to use an herbicide, they recommend Rodeo. Regarding the use of fertilizer — the DNR and SWCD do not recommend fertilizer for native plants. You can always add compost if needed.

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Dear Master Gardener: Are there any “tricks of the trade” for planting and designing containers?

Answer: Container gardening can be a rewarding way to grow plants and add interest to your landscape. There are many containers from which to choose: terra cotta, concrete, ceramic, fiberglass, lightweight foam, and plastic. Each one has advantages and disadvantages, but keep in mind that good drainage will make the difference in how successful your containers will be. To prevent blockage and water build-up, place a piece of landscape fabric over the drainage holes. I use an unbleached coffee filter if the pot is smaller. A good potting soil will allow the roots of the plants to thrive by providing air circulation plus holding moisture in without staying too wet. Look for brands of potting soil that contain Canadian sphagnum peat moss or coconut coir, ground bark, and/or perlite. Some brands contain a small amount of fertilizer as well.

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In regard to design, use a thriller, spiller, and filler. Place the tallest plant in the back center or center (thriller), smaller plants around the base of the tall plant (fillers), and trailing plants at the container’s edge to spill over the side (spillers). Determine your color scheme. If you would like a more formal look, choose one color and for a less formal look, choose several colors. Try adding some edibles — herbs and lettuces make good fillers; mini-cucumbers or grape tomatoes make lovely spillers. Choose plants that grow well together and have the same water and light requirements. Check tags for light requirements; full sun means six or more hours of sunlight, part sun/part shade is three to six hours of sunlight (preferably in the morning) and full shade is less than three hours of direct sunlight. Fertilize with a liquid fertilizer every two weeks.

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Dear Master Gardener: I am interested in planting a garden that attracts butterflies. What plants do you suggest?

Answer: Some butterflies, such as the Painted Lady and the Monarch, migrate from the south arriving in Minnesota in May and June respectively. Because other types of butterflies lay their eggs here, you will want to provide for them as caterpillars, too. Female butterflies lay their eggs on very specific plants that provide the noxious chemical the caterpillar needs. Most caterpillars feed on the leaves of these plants.

The key to attracting butterflies all season is to ensure that there are always nectar producing plants blooming. Nectar gives butterflies the energy they need for reproduction and flight. Butterflies are most active in mid to late summer, so it is important to have flowers that are in bloom at that time. Annuals bloom throughout the summer and provide a good source of nectar. Some annuals that attract adult butterflies are flowering tobacco, marigolds, phlox, and verbena. Perennials that are popular with butterflies are butterfly weed, purple coneflower, asters, yarrow, sedum, bee balm, daisies, chrysanthemums, and plants in the mint family. Some shrubs that attract butterflies are azaleas, blueberries, and lilacs.

To maintain a healthy environment for butterflies and bees, which help pollinate plants, it is extremely important not to indiscriminately use pesticides in your yard. If it is absolutely necessary, use a spot treatment on plants with pest insects. Try to use horticultural oils and soaps and microbial insecticides (for example, Bacillus thuringiensis). Keep in mind that these products will still kill caterpillars. If unwanted caterpillars are defoliating your plants, you can hand pick them off and drop them into a bucket of soapy water, which will kill them.

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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.