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Thursday, June 29, 2017

Gypsy moth quarantine established in Minneapolis

Jeffrey Hahn, Extension Entomologist

The following information was slightly edited from a Minnesota Department of Agriculture news release.

The Minnesota Department of Agriculture (MDA) is placing a gypsy moth-infested area in the Lowry Hill Neighborhood of Minneapolis under quarantine beginning July 1 after a neighborhood resident reported a large insect population. The quarantine will be in place until early next summer.
The quarantined area extends from Mt. Curve
Avenue on the north to Franklin Avenue West
on the south, and Irving Avenue South on
the west to Dupont Avenue South on the east

The MDA was contacted earlier this month by a resident in the neighborhood who suspected a gypsy moth infestation after he noticed caterpillars on trees. MDA staff conducted a survey and found thousands of gypsy moth caterpillars that had already started defoliating trees.

Gypsy moths have caused millions of dollars in damage to forests in the eastern United States. The moths are common in Wisconsin and are now threatening Minnesota. If present in large numbers, gypsy moth caterpillars can defoliate large sections of urban and natural forests. They feed on over 300 different types of trees and shrubs.

What does the temporary quarantine do?
  • The quarantine restricts the movement of trees and woody material, including firewood, out of the area. Trees may be pruned, but all branches and woody material must stay on the property (even if limbs are chipped, gypsy moth eggs are still viable). Grass clippings can be removed from the area. 
  • The quarantine requires self-inspection of any equipment, household items, or vehicles that are sitting outside in the quarantined area and are being moved out of the quarantine. This includes items such as wood pallets, patio furniture, grills, and trampolines, as well as trucks, campers, and boats. Residents should look for gypsy moth egg masses which are brown, fuzzy blobs the size of a quarter. They should scrape the egg masses off the item or leave the item where it is.
A mature gypsy moth caterpillar.  Photo: MN Dept. of Ag.
The gypsy moths likely came to Minneapolis through the movement of infested wood or outdoor items. This raises the importance of the quarantine. Residents can help contain this pest by not moving branches, firewood, or outdoor items out of the quarantined area.

To provide more information, the MDA will be hosting an open house about the quarantine.
Open House
Tuesday, July 11, 6:30-8:00 p.m.
Kenwood Community Center
2101 W Franklin Ave.
Minneapolis, MN 55405

The MDA has set up gypsy moth traps throughout the area to determine the extent of the infestation. Next year the MDA plans to treat the area for gypsy moths and will then lift the quarantine. The department will provide more information this winter about the proposed treatment, which is similar to treatments done in Richfield and Minneapolis in 2016, and Minnetonka, Eden Prairie and Edina in 2011.

For more information regarding the quarantine or gypsy moth, visit If you suspect a gypsy moth infestation in your area, contact the MDA’s Arrest the Pest line at 1-888-545-6684 or

To see the original MDA news release, go here.

Look for Leaf Spots

Angular Leaf Spot on Cucumber
M. Grabowski, UMN Extension
M. Grabowski, UMN Extension Educator

Recent rains and warm weather has provided ideal conditions for many leaf spot plant pathogens to spread and infect young vegetable plants. Leaf spot diseases are caused primarily by fungi and sometimes by bacteria. These plant pathogens survive from one season to the next in previous years infected plant debris and garden soil. Rain splashes fungal spores or bacteria from the soil onto the lower leaves. If the conditions are favorable (typically warm and wet) the pathogen infects and a leaf spot forms.

Young early blight leaf spots can
result in fruit rot later in the summer.
M. Grabowski, UMN Extension 
Leaf spots will soon produce a new set of fungal spores or bacteria that will spread to form new leaf spots. This cycle can continue throughout the summer as long as weather conditions are favorable. By August, entire leaves or plants are blighted brown and some leaf spots have become fruit spots or rot.

What’s a gardener to do?

  • Inspect plants now. Look at the lower leaves that are closest to the soil.
  • Pinch off leaves with leaf spots and remove them from the garden. They can be disposed of in a backyard compost pile that heats up to 148 F or brought to a municipal compost facility. Never remove more than 1/3 of the total leaves on the plant or you will be doing more damage than the pathogen!
  • Do not work in the garden when leaves are wet from rain, dew, or irrigation. Leaf spot
    pathogens are easily spread on hands and tools when leaves are wet.
  • Mulch the soil. Straw, wood chips, and plastic mulches provide a barrier between leaf spot pathogens in the soil and the lower leaves. Mulch also reduces humidity in the plant canopy.
  • Stake vining plants like runner beans, cucumbers, tomatoes, and peas. This will lift the plants farther away from pathogens in the soil and will help the leaves dry quickly after rain or irrigation.
  • Tomatoes staked and mulched, with the
    lower leaves pinched off.
    M. Grabowski, UMN Extension 
  • Pull those weeds! Weeds crowd the crop and create a moist humid environment favorable to leaf spot pathogens. Some weeds can also become infected with leaf spot pathogens and allow the pathogen to remain in the garden and spread to the vegetable crop despite a gardener's best efforts.

It is difficult to slow down a leaf spot disease once it has spread throughout the plant. Use the cultural control practices now to slow down these pathogens before they get started. Learn more about how to grow healthy vegetables at the University of Minnesota Extension Garden webpage

Grasses that self-seed

Mary H. Meyer, Extension Horticulturist and Professor, University of Minnesota

Is a plant that grows easily from seed a good thing or a bad thing? Perhaps it depends on how much you like the plant! Grasses that self-seed and come up throughout the garden can be an asset or a liability. Listed below are native and non-native grasses that I have seen self-sow in Minnesota growing conditions.  I have noted which are native and ranked them in two categories: very likely (VL) to seed and somewhat likely (L), because to make this list, they all sow seeds.

The worst offender across the U. S. is Miscanthus sinensis, which is listed on many state’s invasive plant lists, and in 2015 New York state regulations started requiring these plants for sale be labeled as invasive plants using specific language. Along a shoreline, it may be advantageous to have native sedges like porcupine and palm sedge that self-sow. I find river oats is marginally hardy so the mother plant may die, but seedlings come up under my silver maple and box elder in these shady hosta and geranium beds where few other plants will grow, so I do not mind seeing these volunteer plants. Removing the seedheads from the plant before they disarticulate (fall apart) is one means of controlling self-seeding grasses.

Self-seeding grasses and sedges
Mace sedge has a distinctive seedhead

mace sedge, Carex greyi, native, likely to self-sow: L
porcupine sedge, Carex hystericina, native, Very likely to self-seed: VL   
palm sedge, Carex muskingumensis, native, VL     
river oats, Chasmanthium latifolium, native to SE U. S., VL           
love grass, Eragrostis curvula 'Wind Dancer', native to SE U. S., L
blue fescue, Festuca species, non-native, L
Siberian melic grass, Melica altissima var. atropurpurea, non-native, VL           
Japanese silvergrass, Miscanthus sinensis cultivars, non-native, L   
two or more cultivars grown together cross-pollinate and set seed; plant only where you can monitor seedlings
River oats grows in sun or shade
tall purple moorgrass, Molinia caerulea ssp. arundinacea, non-native, L   
Mexican feathergrass, Nassella tenuissima (annual), native to SW U. S., VL           
panic grass, Panicum capillare 'Frosted Explosion' (annual), native, VL
switchgrass, Panicum virgatum, native, L           
fountain grass, Pennisetum alopecuroides, non-native, VL           
little bluestem, Schizachyrium scoparium, native, L       

Wednesday, June 28, 2017

Watch your garden for squash vine borers

Jeffrey Hahn, Extension Entomologist

If you are growing squash, pumpkins, cucumbers, or melons in your garden this year, now is a good time to start monitoring for squash vine borers. Squash vine borer larvae bore into the stems, causing plants to wilt and eventually die. The best management is well timed insecticide treatments when adults are active and laying eggs.

Adult squash vine borers are day-time flying moths that resemble wasps. They are about 1/2 inch long with an orange abdomen with black dots. The first pair of wings is an iridescent green while the back pair of wings, which may not always be seen, is clear.

Squash vine borer adult laying eggs.  Photo: Jeff Hahn,
University of  Minnesota Extension
There are a couple of methods for detecting them in your garden. You can watch for them flying around while you are in your garden; they are conspicuous and easily noticed. You can also place yellow containers (like pans or pails) half filled with soapy water. These moths are attracted to yellow; when they fly to the container, they will fall in to the water. It is then an easy matter to check the container for their presence.

As soon as you spot one squash vine borer, start treatment. There are a variety of insecticides that can be applied. If you don’t see any but have a history of these pests in your garden, begin treatment by late June or early July (the further north you are located, the later the moths will emerge).

For more information, including management, see Squash vine borer management in home gardens.

Tuesday, June 27, 2017

Jumping worms in Minnesota

Lee E. Frelich, Director of the University of Minnesota Center for Forest Ecology and Laura Van Riper, Terrestrial Invasive Species Program Coordinator, Minnesota Department of Natural Resources

The arrival of jumping worms in the Midwest has made news headlines during the last 2-3 years. Native to Asia, jumping worms have the ability to infest soil at high densities, change soil structure and chemistry, and damage roots of plants in nurseries, gardens, forests, and turf grass. Relatively little is known about them compared to the European earthworms that have been present since European settlement, and the following summarizes the state of knowledge at this time.

Jumping earthworms are more properly known as Pheretimoid worms. Sixteen species originally
A commonly encountered jumping worm, Amynthas agrestis.
Note how the clitellum (band around the worm) is not swollen and is relatively close to the head.  Photo: Josef
Görres, University of Vermont
from Japan and Korea are known in North America north of Mexico, in four genera Amynthas (10 species), Metaphire (4 species), Pithemera (1 species), and Polypheretima (1 species). The taxonomy of these genera is in a state of flux and at this time we do not know exactly how many species there are in their native Asian habitats. They can be differentiated from the more common European earthworms (13 species from 8 genera are known in Minnesota), including the often seen nightcrawler (Lumbricus terrestris) and rose angle worm (Aporrectodea rosea), by their annular clitellum (band around the worm about 1/3 of the body length back from the head), which is smooth and constricted, as opposed to the swelled saddle-like clitellum of European earthworms.

European earthworm (nightcrawler), Lumbricus terrestris.
Note how the clitellum is swollen and further back from the
head.  Photo: Michael Linnenbach, Wikipedia
Of the 16 species present in North America, a few species of Amynthas and Metaphire are most common in the Great Lakes and northeastern U.S. The jumping worm A. agrestis, has been found from Wisconsin and Minnesota across to New England. Metaphire hilgendorfii and A. tokioensis have similar geographic distributions, and A. loveridgei was also reported in Minnesota in 2002. Amynthas worms have been found in several places in Minneapolis. Another as yet unidentified species found on St. Paul campus of the University of Minnesota is about four inches long and chocolate brown with a metallic sheen. Note, however, that little is known about distributions of these earthworms within Minnesota, as compared to European earthworms which have been the subject of many studies. Studies of earthworms from Asia in Minnesota are just beginning.

Although one of the species present in North America can live more than one year (A. corticis), for the most part, jumping earthworms are annuals. In other words, they hatch from cocoons in the spring, grow rapidly and exist as mature adults from early summer to fall, and die during the winter, after laying plenty of cocoons—which are much more tolerant of temperature and moisture extremes than the worms—to hatch the following spring. This contrasts to the European nightcrawler that hibernates several feet down, below the frost line, and lives several years.

Jumping earthworms are apparently being distributed in mulch (both commercial and from community compost piles), are known to be able to survive in shredded pine, cedar and spruce mulch, and have been frequently observed in mulched garden beds. Some species have a lignin-eating enzyme called peroxidase, which allows them to eat fibers of wood in mulch. Because most commercial mulches are heat treated to temperatures that are lethal to earthworms and their cocoons, it is a mystery as to how the jumping earthworm contamination into mulch occurs. This route of distribution contrasts with European earthworms, which originally arrived in ship ballast and potted plants, and are now spread across the landscape in potted nursery stock and into even remote areas as live fishing bait.

The previously mentioned A. agrestis worm can be very large - the size of nightcrawlers - six inches or more long. A. agrestis worms occasionally swarm in one area and can tear up the soil. Several years ago, a swarm of them destroyed a garden bed with hostas and other plants in Loring Park in downtown Minneapolis. When I examined the wilted hostas, I was surprised to find that they were not attached to the soil. The worms had turned the soil into pellets like cat litter and jumped every direction when I stuck my finger in the soil. Occasional irruptions with very large populations coupled with swarming behavior lead to concerns about damage to gardens, lawns, nurseries, and native plants in natural areas.

The Minnesota Department of Natural Resources (DNR) has convened an Amynthas working group to examine the known information about jumping worms and to make recommendations to the DNR leadership if there are particular regulations that make sense. The working group is composed of stakeholders such as representatives from the Minnesota Nursery and Landscape Association, the Minnesota Department of Agriculture, University of Minnesota, DNR Fisheries division, and DNR Ecological and Water Resources division. The DNR continues to stress to boaters and anglers to dispose of all unwanted bait in the trash can.

Wednesday, June 21, 2017

SWD out now!

Jeffrey Hahn, Extension Entomologist

The first spotted wing drosophila (SWD) adults were detected in Minnesota last week, collected in
Adult male spotted wing drosophila (note the black spot at the
tip of the wing). Bob Koch, Univ. of MN Extension
traps at the Rosemount Research and Outreach Center. If you are growing susceptible fruit in your gardens, including raspberries, blackberries, blueberries, cherries, strawberries, or grapes, be sure to set out traps to determine when SWD is first active in your area. SWD is a very destructive invasive insect pest that can severely damage untreated susceptible fruit crops.

The best approach to managing SWD is through detection, sanitation, and insecticide treatments. For more information on SWD see Spotted wing Drosophila in home gardens.

Tuesday, June 20, 2017

Dutch elm disease active now

M. Grabowski, UMN Extension

Leaves turn yellow, then brown and wilt on a Dutch
elm disease infected elm tree.
M. Grabowski,  UMN Extension 
Although not as common as they once were, many American elm trees can still be found throughout Minnesota.  In late spring and early summer the first symptoms of Dutch elm disease begin to appear. Gardeners with elm trees on their properties should watch for leaves that wilt, turn yellow, and then brown. This may happen to leaves on just one branch or on multiple branches throughout the canopy. Leaves may fall off the tree and be scattered on the lawn below.

It is important to react quickly if symptoms of Dutch elm disease appear. The infection can be pruned out if the fungus has not yet reached the main trunk of the tree. This requires pruning out the infected branch 5 to 10 feet below symptoms of the infection to be successful. Gardeners that suspect Dutch elm disease should contact a certified arborist to inspect the tree and submit a sample for diagnosis to the UMN Plant Disease Clinic.

Young Accolade elm in a landscape. This tree
is Dutch elm disease resistant.
M. Grabowski, UMN Extension 

There are many varieties of elm that are resistant or tolerant of Dutch elm disease that are now available in nurseries. Gardeners looking for a new shade tree should consider planting an elm with Dutch elm disease resistance. Elms are fast growing, resilient trees that tolerate many common stress factors found in urban sites. 

Thursday, June 15, 2017

After the storm

M. Grabowski, UMN Extension Educator

Strong winds and hail have caused significant damage to plants large and small in Minnesota landscapes. Here's what gardeners need to know about treatment and recovery of storm damaged plants.


Storms often reveal hidden rot that
weakens trunks or large branches.
M.Grabowski, UMN Extension
Storm damaged trees may be unstable and can be a hazard to people and property. Contact a certified arborist to evaluate and treat large trees that have suffered from storm damage.

Smaller branches that have been damaged by the storm, are low in the canopy, and accessible from the ground can be treated by the gardener. Prune off branches that are split, cracked, or torn at a point where the wood is undamaged. A tree will heal over small scattered wounds from hail but severely hail damaged branches should be pruned out. A clean pruning cut at a branch union allows the tree to naturally heal over the wound site. A proper pruning cut does not leave a branch stub or remove bark beyond the branch collar. Painting over pruning wounds is unnecessary unless the tree is an oak tree.

Minnesota is currently in the high risk season for oak wilt infection. Sap beetles are attracted to fresh wounds in oak trees and can introduce spores of the oak wilt fungus, which are attached to their bodies. If oak trees have been damaged in recent storms, prune to remove damaged branches and then immediately paint over the wound with water-based paint, a pruning/wound sealer, or shellac.
Hail damage on hostas.
M. Grabowski, UMN Extension

Flower garden

In the flower garden, broad leaved perennials like hostas were most severely damaged by recent hail storms. Long tears in the leaf are signs of hail damage. The plants will tolerate leaf damage and produce new leaves as long as the growing point of the plant is undamaged. Gardeners can prune out the most severely damaged leaves. Do not remove more than one third of the plants foliage however, as the plant will need energy produced by its leaves to recover and produce a new flush of leaves.

Hosta leaves torn by hail
M. Grabowski, UMN Extension
Stems of annual or perennial plants that have been broken by the storm should be pruned back to the next undamaged leaf. Many flowering plants can produce new shoots from buds on the side of the damaged stem or from the crown of the plant. Annual flowering plants that were broken off at the soil level are unlikely to recover at this point however as the plants are not well established this early in the growing season. These plants should be removed and replace.

Vegetable garden
Eggplant leaves with hail damage
M. Grabowski, UMN Extension

Storm damage to vegetables in the garden will vary based on how well established the plants are. Spring greens like spinach, lettuce, bok choy, and Swiss chard likely suffered torn leaves from hail and wind. Plants will recover as long as the growing point is undamaged. Young newly emerged seedlings may have escaped damage due to their size or have been killed completely by a direct hit. Gardeners should evaluate vegetable plants over the next week. Young seedlings that produce new leaves are likely to recover. Seedlings that fail to produce new growth should be removed and replaced.

The apples will bear scars of
hail damage even at harvest
M. Grabowski, UMN Extension
Transplants with a central stem need to be evaluated carefully. A tomato or broccoli plant will tolerate and recover from tearing of the leaves. If the stem breaks near the soil level, however, it is best to remove and replace the plants. Tomatoes, peppers, and eggplants that suffer a break in the stem higher up may sprout from buds on the side of the stem and recover. Broccoli, cauliflower, and cabbage that lose their central growing point however may recover but will likely produce multiple small heads as opposed one large head. Reseeding of broccoli, cauliflower and cabbage can be done in early July where storms have significantly damaged the spring crop to produce a fall crop.

Disposal of plant material
In Minnesota yard waste cannot be sent to the landfill. Place all plant material in a backyard compost bin or bring it to a municipal compost facility.

Friday, June 2, 2017

Creeping charlie: Management and value to pollinators

By: James Wolfin and Phoebe Koenig, University of Minnesota Bee Lab 

Range of creeping charlie (Glechoma hederacea L.)
in North America. Credit: USDA Plants database
Creeping charlie (Glechoma hederacea L.), also called ground ivy, is an herbaceous perennial native to the British Isles and present in North American landscapes for nearly 200 years. While some consider creeping charlie to be a weedy species, others consider it to be naturalized, and some seed providers will sell this flower as a form of ornamental ground cover. Creeping charlie is in the Mint family and an early spring bloomer (April-May) easily recognized by its small, pale violet flower. It grows well in shaded areas with fine-textured soils that are damp and slightly acidic to slightly alkaline (pH 5-7.5). Like other mints, creeping charlie spreads rapidly through stoloniferous growth, where stems grow at the soil surface and spread laterally. These stems are commonly referred to as “runners” and allow creeping charlie to grow in its easily identifiable mat-like form of ground cover (Hutchings and Price 1999).

Creeping charlie can form
a thick mat in lawns
Creeping charlie and lawns
Creeping charlie is considered by many to be a nuisance weed in lawns and will infiltrate areas that  have been neglected or otherwise poorly managed. Once established within a lawn, creeping charlie may suppress the growth of surrounding plants, due to a characteristic called “allelopathy”. An allelopathic plant will produce biochemicals that deter the fitness of surrounding plants. One study (Rice, 1986) found that flowers growing alongside creeping Charlie experienced decreased seed germination and faster rates of root and shoot growth.
Fine fescue coverage in a heavily
shaded environment.
An effective way to exclude creeping charlie from your home lawn is by practicing responsible lawn species selection. In shaded areas where creeping charlie often thrives, it is important to utilize grasses like the fine fescues (Festuca spp), which are known to perform well in Minnesota. In the northern climates of the United States, Kentucky bluegrass is the most common species of turfgrass. While Kentucky bluegrass is a high quality turfgrass that performs well in terms of winter hardiness, this species of grass struggles in shady areas. Both tall fescue (Festuca arundinacea) and fine fescue (Festuca spp.) are cool-climate turfgrass species that do well in shady areas. Mixing fescues with Kentucky bluegrass is an effective way to ensure that strong turfgrass density is present despite the shade provided by common yard trees. In addition to employing careful turfgrass species selection, it is important to utilize best practices in lawn care including mowing, irrigation, and fertilizer to ensure proper turfgrass health and density. management.

When creeping charlie is present in low numbers, it may be possible to control the weed via hand weeding. When hand weeding, it is critical to remove the roots as well as the above ground portion of the plant to ensure that there is no re-emergence.  Due to the aggressiveness of creeping charlie, it may be necessary to weed the area several times to remove all creeping charlie vegetation and use proper lawn care practices to promote a healthy, thick lawn instead of creeping charlie.  A study by Price and Hutchings (1986) noted that creeping charlie is less abundant when turfgrass is present, as the grass provides competition for sunlight and soil nutrients. Increasing access to sunlight will improve turfgrass growth, limiting the ability of creeping charlie to spread through the turf lawn. 

When creeping charlie has overtaken turf
There are several options for eradicating creeping charlie when it has taken over a lawn. Typically use to cut sod for lawn renovation, a sod cutter may also be used to quickly remove strips of weeds, like creeping charlie, from a lawn. This will result in an area of bare soil within the lawn. Be sure all creeping charlie vegetation is eradicated to prevent re-invasion. If any piece of plant material is not removed, there is potential for creeping charlie to re-establish within the lawn. After all creeping charlie vegetation is removed, the areas of bare soil should be seeded with high quality turfgrass suited to the site conditions (soil type, amount of sun/shade, plant hardiness zone) to ensure dense, uniform germination throughout the area.  Lawns with dense turfgrass coverage are less susceptible to weeds like creeping charlie. 

Solarization strip installation
Credit: Xerces Society
A second option for removing a large area creeping charlie from a lawn is through solarization, a method for killing plant material and soil pests that involves anchoring clear plastic sheeting over the area during the warm months of spring and summer. The clear plastic sheet captures heat and sunlight, raising temperatures to the point where grasses and weeds can no longer survive. Solarization is best fit for sunny, flat sites that are less than 1/4 of an acre in size. Note: In cooler, shaded areas (where creeping charlie is likely to be found) the process of solarization takes the better part of a growing season, typically 5-6 months, or up to a full year in some instances. Additional information on solarization can be found through the Xerces Society.

The plastic should be removed in the late fall when soil temperatures are 35-55°F so that the area can be dormant seeded. Dormant seeding is done at these temperatures because the soil is too cold for germination to occur, but the ground is not yet frozen. This ensures that the target species seeded into the newly prepared area will germinate in the spring when temperatures have reached the proper number of degree days. If seeded properly, the new turfgrass area should be dense, uniform, and free of weed pressure.  

An additional strategy for removing a creeping charlie infestation is the use of chemical herbicides, specifically herbicides that include glyphosate and/or triclopyr as active ingredients. While this can be a less ecologically-friendly solution, it is an effective form of weed management. Applications of herbicides are most effective on warm, calm days when plants are actively growing. It is important to avoid windy days to ensure that herbicide applications do not drift onto non-target plants. Glyphosate treatments are most effective when two treatments are applied, with the second treatment taking place 7-10 days after the initial treatment. After the creeping charlie has been removed, high quality grass seed should be overseeded onto the turf lawn.   

IMPORTANT: A pesticide label is a legal document. Always follow the pesticide label directions attached to the pesticide container you are using. Pesticide labels may change frequently. Internet labels may not match the label on the container you are using. The site of use or plant to which the pesticide is to be applied must be listed on the label or the pesticide cannot be used. Remember, the label is the law.

Value to bees and other pollinators
Bumble bee foraging on creeping charlie flower
For people that live in an area where letting creeping charlie grow is not a problem for neighbors, creeping charlie employs a unique strategy to attract some bee visitors, such as sweat bees, bumble bees, and honey bees, that is tied into how the flower produces nectar. The flowers have a unique strategy for rewarding visitor pollinators, commonly referred to as the “lucky hit” strategy.  Creeping charlie flowers produce an average of 0.3 ml of nectar per flower, but the amount of nectar in any one flower varies greatly, ranging from 0.06-2.4mL.  When 805 creeping charlie flowers were sampled for nectar quantity, it was found that only 8% (64/805) of these flowers had a large volume of nectar, and the rest had almost none (Southwick et al. 1981).  The availability of nectar also varies throughout the day. As the morning fades into afternoon, “lucky hits” become less frequent, as creeping charlie flowers do not replenish their nectar throughout the day. Most flowers produce their nectar at night or in the early morning, so it is believed that all the “lucky hits” available in the afternoon are ones that were missed by bees earlier in the day.  One researcher (Southwick et al. 1981) found that bees foraging on creeping charlie for 5.9 minutes obtained enough nectar from the flowers to make foraging energetically profitable.

While creeping charlie can be a good nectar source, we are not recommending that you let it take over your lawn. In addition to the issues associated with nectar production, pollen (the main protein source for bees) from creeping charlie is not readily available to visiting bees and other insect pollinators. Bees need a variety of food sources, and the best lawns have many kinds of flowers, hopefully with a range of bloom times. Creeping charlie is invasive and can prevent you from growing additional flowers in your lawn. Instead, if you are looking to promote pollinator health in your lawn or garden, we recommend planting a diversity of flowers that produce high quality nectar and pollen consistently. That being said, if your lawn/garden is already overrun with creeping charlie, and you have not had a chance to eradicate it yet, you can at least take pleasure in seeing the bees buzzing around it, and note when they spend extra time on one bloom. They are likely hitting the jackpot!

Dickinson, R. and Royer, F. Weeds of North America, University of Chicago Press, Chicago, IL. 2014

Foord, K. 2016. The value of lawn weeds for pollinators: Not all weeds are created equal. Yard and Garden News, University of Minnesota Extension. Accessed 06/19/17 

Hultén, E. 1971. The Circumpolar Plants. II. Dicotyledons. Almquist & Wiksell, Sweden.

Hutchings, M.J., Price, E.A.C. 1999. Glechoma hederacea L. (Nepeta glechoma Benth., N. hederacea (L.) Trev.)

Rice, E.L. 1986. Allelopathic growth stimulation. The Science of Allelopathy (eds A.R. Putnam & C.S. Tang), pp. 34-40. Wiley, Chichester, UK.

Southwick, E. E. "Lucky Hit" nectar rewards and energetics of plant and pollinators." Comparative Physiology and Ecology 7.2 (1982): 51-55.

Southwick, Edward E., Gerald M. Loper, and Steven E. Sadwick. "Nectar production, composition, energetics and pollinator attractiveness in spring flowers of western New York." American Journal of Botany (1981): 994-1002.

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