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Extension > Yard and Garden News > Garden offenders: get a jump on four common problem plants

Thursday, April 21, 2016

Garden offenders: get a jump on four common problem plants

Julie Weisenhorn, Extension educator

Typically people contact Extension with the question "How can I get get rid of  __________?" (fill in with a troublesome plant). Unfortunately, these offenders are well-established by the time we usually get this call. So here are four of the most common problem plants and what they look like now in their emerging stage, so you can get a jump on getting them out of your yard and garden!

Buckthorn in springtime
Buckthorn (Rhamnus cathartica)
Public enemy #1, buckthorn was introduced as a hedge plant. Buckthorn was a favorite of urban homeowners for its interesting cherry-like bark, tolerance to many growing conditions and its receptiveness to pruning. Today, common or European buckthorn as well as glossy buckthorn (Frangula alnus Mill.)  are listed on the Minnesota Department of Agriculture Restricted Noxious Weed List. Buckthorn is leafing out right now and can be easily spotted by its silvery-gray park with white lenticels, bright green, rounded young leaves and the sharp thorn on the ends of branches. Guidelines for removal can be found on the Minnesota Department of Natural Resources buckthorn webpage.
Silvery buckthorn bark
with white lenticels

Thorn on young buckthorn

Garlic mustard (Alliaria petiolata)
Also listed on the Minnesota Department of Agriculture Restricted Noxious Weed List, this biennial
Young garlic mustard plant
 plant is stealthy. Its cute, tidy rosette of scalloped leaves can sometimes be mistaken for more desirable ornamentals like hollyhocks. Beginning gardeners or gardeners new to the area may be afraid to remove it.  An easy identifying feature: garlic-scented leaves. (Plan to throw away your gloves after pulling these plants). As a biennial, garlic mustard puts its energy into leaves and roots the first season, and blooms the second season. If left alone, the small clusters of white flowers result in hundreds of tiny seeds, making is a prolific invader of our woodlands. This is one plant that warrants chemical spot treatments.
For more: Minnesota Department of Natural Resources garlic mustard page.


Creeping charlie (Glechoma hederacea)
Early blooming creeping charlie
Not a Smart Gardens radio show goes by without a creeping charlie question - even in the winter! A member of Mint family and like other mints, it spreads by means of stolons (surface roots). Though not a registered noxious weed the Minnesota Department of Agriculture, it is considered invasive by the Minnesota Department of Natural Resources and can be a tough plant to eliminate once it has become established though some homeowners have come to tolerate it because it attracts and provides food for pollinators (one of its few redeeming qualities). It is a very adaptable plant and grows well in moist soil in part shade / full shade sites where lawn grass is thin and not very robust. This may be in compacted soils, shady locations, and weedy sites. Therefore, treating with an appropriate product, maintaining a healthy lawn, utilizing shade tolerant grasses, and choosing alternative ground covers in areas not suitable for growing lawn grasses will help manage weeds including creeping charlie. More on creeping charlie

Creeping bellflower (Campanula rapunculoides)
Creeping bellflower emerges early
Creeping bellflower forms a mat
Campanula cultivars are favorite perennials of gardeners, and Campanula rotundifolia, harebell, is a Minnesota native wildflower and a tough plant that grows in rocky, dry soil. However, its European cousin, the creeping bellflower (C. rapunculoides) is an aggressive plant and not so well-liked. Creeping bellflower forms mats of thick, tuber-like rhizomatous roots. It is a prolific seeder and quickly outcompetes more desirable plants for moisture and nutrients. This plant leafs out early, making it easy to spot treat with a broadleaf herbicide and easier to remove by hand while desirable plants are still emerging. For more details: Minnesota Wildflowers,
Wisconsin Department of Natural Resources

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