Ask the Master Gardener: Moths often mistaken for hummingbirds are no threat to flowers

Hummingbird moths and white-lined sphinx moths will not cause harm to flowers.

A hummingbird moth on flowers. Photo by Jackie Burkey

Dear Master Gardener: I saw an insect that looks and flies like a hummingbird. What is it and can it damage my flowers?

Answer: The insect you most likely saw, and that frequently gets mistaken for a hummingbird, is a moth. The hummingbird moth, or hummingbird clearwing, has a wingspan of 1½ to 2¼ inches, and lacks scales on most of its wings, with the exception of a dark border around the edge of its wings. Another moth that hovers around flowers like a hummingbird is the white-lined sphinx moth. This moth is larger than the hummingbird moth, has a wingspan of 2 to 3½ inches, and has scales covering its wings. Its first pair of wings are dark colored with a white stripe running from the wingtip diagonally to the base of the wing, and the second pair of wings is dark with a pink-red band. Like hummingbirds, both moths hover and flit about in flower gardens. Whereas a hummingbird has a long beak, these moths have a long proboscis that they use to feed on nectar while hovering. They prefer feeding on deep-lobed flowers. Moths are the preferred food of birds, so most moths fly at night to avoid being consumed; however, these hummingbird-like moths fly during the day. You will most likely see these moths feeding around dusk and active in July through September. Their nectar-sipping activity causes no harm to flowers.

Dear Master Gardener: I know how important it is to protect bees because they are pollinators. What about yellowjackets? We have a lot of yellowjacket and wasp nests in various places around our house and several people have gotten stung. Should they be protected too or can we go ahead and kill them?

Answer: Unlike honey bees, yellow jackets are not important as pollinators and extraordinary measures need not be taken to protect them. Yellowjackets (which include bald-faced hornets) and paper wasps are two types of social wasps found in Minnesota. Honey bees and bumble bees are social bees found in Minnesota. Wasps commonly nest on buildings or in retaining walls, trees, and the ground. When wasp nests are found close to where people are active, the nests should be eliminated to minimize the risk of stings. Honey bees mostly occupy manufactured hives, but occasionally nest in cavities of large trees or other protected areas. Bumble bees are usually found underground in deserted rodent nests or other cavities, in compost piles, or underneath objects on the ground. Both honey bees and bumble bees construct cells made of wax. Honey bee and bumble bee nests are typically not a problem and should be preserved whenever possible.

To get rid of yellowjacket and paper wasp nests it is best to treat them late in the evening or early in the morning when they are less active. If after a day you still see them flying around, repeat the treatment. If you can see the nest (like those attached to eaves), you can treat it using an aerosol spray labeled for wasps and hornets. For yellowjackets, spray it directly into the opening of the nest where they fly in and out.


Dear Master Gardener: Why is purple loosestrife a noxious weed? It looks so pretty along the edges of swamps.

Answer: Purple loosestrife (Lythrum salicaria) is a European native that has no native enemies here to keep it in check. When conditions are right it can spread throughout a wetland in a single season. It will crowd out native vegetation necessary for food and habitat for native species of plants, animals, and fish. When purple loosestrife gets a foothold, the habitat where fish and wildlife feed, seek shelter, reproduce and rear their young, quickly becomes choked under a sea of pretty purple flowers. In addition, areas where wild rice grows and is harvested and where fish spawn are degraded. Purple loosestrife is a prohibited invasive species and according to Minnesota statute the owner or occupant of private land is responsible for controlling or destroying noxious weeds to prevent their spread. Yes, purple loosestrife is pretty but as Grandma says, “Pretty is as pretty does.”

Dear Readers: The Minnesota Department of Agriculture (MDA) has been receiving reports of residents receiving unsolicited packages of seeds appearing to come from China. Minnesotans should do the following if they have received unsolicited packages of seeds.

  • Do not throw away the package or its contents.

  • Do not plant the seeds!

  • Contact Arrest the Pest line at 888-545-6684 or and provide your name, contact information, and the date the package was received. Officials will coordinate shipping the packaging and contents to the MDA Seed Program.

August Gardening Tips

  • Iris become dormant and slow their growth this month, so now is the time to divide them if needed. Bearded iris flower better when they are regularly divided. Cut the foliage back to 6-8 inches and keep one or two foliage clusters per rhizome.

  • Early to mid-August is a great time for planting grass seed. Warm soils and less weed competition improve chances for successful lawn establishment before winter.

  • Create a compost pile with grass clippings, leaves, garden debris (plant material), egg shells, and fruit and vegetable scraps. Warm August weather encourages the rapid breakdown of materials by bacteria. Keep it moist and turn it frequently to maintain an aerobic environment to speed up the breakdown process. According to the EPA, home composting can divert 700 pounds of waste per household per year from municipal waste. And – you’ve just created your own “gardener’s gold” to enrich your soil!

  • Continue to deadhead perennial flowers to prevent them from setting seeds, and to reserve energy for next year’s blooms.

  • Keep picking zucchini, cucumbers, snap beans, and other vegetables from your garden, even if they are past their prime. Plants remain more productive, and there will be less rotting produce around to attract yellowjackets (wasps).

  • To avoid Tomato Blossom End Rot, water your tomato plant consistently and evenly.

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 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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