Be on the Lookout: Three New Non-native Plants Invade Minnesota

Could it actually be that the groundhog was a bit off this year? We hit 62 degrees in the Twin Cities the other day, a tornado touched down, and ice sheets are quickly disappearing off of our local lakes. Is it possible that spring will be arriving quite early to Minnesota, in spite of the behavior of our furry animal indicator?

In the blink of an eye, we will have our stark brown landscape quickly turning to a lush carpet of green. So, let's take a closer look at our landscape and the "native" and "non-native" plants that make up this community. What we call "native" species are those plants that historically occurred in a given region or habitat prior to European settlement. Invasive "non-native" species are the troublemakers.  They are brought into a region that they did not historically populate and run wild, causing environmental and economic loss. A "weed" is a more generic term for a plant that is simply growing where it is not wanted. Weeds can be native or non-native plants.

Those invasive troublemaker species are popping up in Minnesota all the time.  Here are three invasive non-native species to be on the lookout this season: Oriental bittersweet, black swallow-wort and Grecian foxglove.  New to our state, these weeds currently have limited, localized infestations.  If promptly controlled, their establishment may be curtailed and their detriment to our environment prevented!

This highly invasive species has steadily spread west and south since its introduction.  Attracted to the abundant fruit, birds gobble up the tasty treats, and freely disperse seed in their droppings.  Oriental bittersweet was commonly planted as an ornamental and its berries were widely used in decorative arrangements and wreaths, furthering its distribution.  These practices are now against the law in Minnesota.

Both bittersweet species are similar in appearance, however, there are a few distinguishing identifiers.  Oriental bittersweet produces fruiting structures with yellow sheaths, in the leaf axils along the entire length of the vine, whereas, American bittersweet only produces orange sheathed fruit clusters at the terminal end of the vine.  

Another invasive species to watch for is black swallow-wort, Cynanchum louiseae.  Commonly referred to as 'climbing milkweed' or 'Black Dog-strangling Vine', black swallow-wort is a European species.  Actually a member of the milkweed family, this species is NOT beneficial to the reproductive cycle of monarch butterflies.  Studies have shown monarch adults will lay eggs on this milkweed, however, the caterpillar larvae cannot use this species as food and subsequently die.

 

2002  © Peter M. Dziuk

Black swallow-wort is a perennial vine growing up to six feet in length, typically occurring in dense patches, smothering and suppressing native vegetation.  Flowers are purple, and the seed is formed in milkweed pods in late summer.

    

Infestations are not normally discovered until the vine has become well established.  This species sprouts readily from its root system, forming dense thickets which can choke out native vegetation. 

© 2002 Peter M. Dziuk

Grecian foxglove was brought to the states from Europe as an ornamental, and eventually escaped cultivation.  Prone to forming large stands, this plant is aggressively displacing native prairie and savanna species where it becomes established.

In Minnesota, Grecian foxglove is a biennial, forming a rosette in the first growing season. During the second year, this invasive species grows rapidly, forming a flowering stalk with distinctive clusters of hairy, cream, tubular flowers containing purple/brown veins.

 

Grecian foxglove spreads exclusively by the copious amount of seed it produces.  Each seed pod has a small hook which easily attaches to animal fur or human clothing, thus facilitating the spread of the species.

New invasive species are a continual problem, but preventing their establishment is a real possibility.  Be on the lookout for these non-native invaders to help preserve our Minnesota ecosystems.

Our well-trained maintenance crew can help you monitor your natural areas for invasive species. We use the most up-to-date treatment methods to control these and other non-native invasive plant species.  Please call us today to discuss your monitoring and maintenance needs!