Ask the Master Gardener: What to do with old wasp nests

Wasp nests only survive for one season and are not reused.

An abandoned wasp nest attached to a pine tree. Photo by Jennifer Knutson

Dear Master Gardener: We have a wasp nest in our pine tree left over from last year. Should we do something about it?

Answer: There is no need to do anything with the wasp nest. Wasp nests only survive for one season and are not reused. The only surviving yellowjackets from last season are new queens and they have spent the winter in protected sites such as under loose bark. When temperatures warm up in the spring the queen becomes active and builds a new papier mâché-like nest where she lays her eggs. When freezing temperatures arrive in the fall, the old queen and all the workers in the nest die. Yellowjacket nests will eventually deteriorate and go away on their own.

Dear Master Gardener: How do I divide my daylilies? Can they be divided this spring?

Answer: Daylilies can be divided every three to five years. The best time to transplant or divide daylilies is early spring or late summer after they are finished flowering. Division promotes more flowers, but keep in mind if they are divided this spring, they may not bloom this summer. Dig up the entire clump and carefully pull the clump apart, or use a sharp knife. Divisions should have two or three fans of leaves with all the roots attached. Replant the divisions so the crown (the part where the stem and root meet) is 1 inch below the soil surface. If needed, add more soil back into the hole to lift the plant up. When the plant is at the right level, back-fill with the soil, lightly packing it down. Water thoroughly to hydrate the plant and settle the soil around the roots.

Gardening idea for children from Penn State University Extension

Two ways to watch seeds sprout:


  1. Line a glass jar with a damp paper towel and put several seeds such as zucchini or bush beans between the glass and the paper towel. Attach the lid and leave the jar on the kitchen counter. Check the paper towel each day and moisten as necessary. Your seeds should sprout in a few days.

  2. Recycle a foil pan and a plastic bag to create a mini greenhouse. Place seeds such as zucchini, scarlet runner beans, cucumbers, and broccoli on a damp paper towel in the bottom of the pan. Put several of each in rows. Draw a simple map showing where each seed variety was “planted” so that it’s easy to identify which seeds sprout first. Encourage the children to make predictions. Put the tray in a plastic bag. Once the seeds and roots grow, talk about germination and how different seeds have different germination periods.

May gardening tips

  • In most years, early to mid-May is a good time to apply pre-emergent crabgrass killer before crabgrass seeds start to germinate and seedlings poke through the soil surface. A natural substitute for synthetic pre-emergence herbicides is corn gluten meal. Apply corn gluten meal at a rate of 20 pounds per 1,000 square feet of lawn; then water it in to activate it.

  • 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.

  • 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 ten 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.

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.

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