Crown Vetch Nightmare

by DerdriuMarriner

A landscape may seem to be pretty in pink with the pink and white flowers of crown vetch. But behind the prettiness is a troublesome non-native invasive plant.

Securigera varia is commonly known as crown vetch or purple crown vetch.

An Old World native plant, crown vetch was introduced in the 1950s into the United States and Canada as ground cover to control erosion.

The nightmare of crown vetch is its ability as a non-native invasive species to dominate its environment to the detriment of native plants.

crown vetch flower

Pohick Creek, Fairfax County, northern Virginia
Pohick Creek, Fairfax County, northern Virginia

 

The common names of Securigera varia (L.) Lassen are crown vetch or purple crown vetch.

A synonym for Securigera varia is Coronilla varia. The synonym’s genus name, a diminutive form of the Latin word corona (“crown”), recognizes the annular (“ringlike”) arrangement of the flowers on their stalk. The common name links crown, for the coronal floral arrangement, with vetch, a corruption of the Latin word vicia (“bean plants”), recognizing that Securigera varia is in the legume family, Fabaceae.

Native to northern Africa, southwest Asia, and Mediterranean Europe, Securigera varia was introduced into the United States and Canada in the 1950s as ground cover in erosion control.

 

closeup of crown vetch lance-shaped leaves

near Přerova, northeastern Czech Republic
near Přerova, northeastern Czech Republic

What crown vetch looks like

 

Growing from a taproot, crown vetch puts forth branching stems which rise vertically and also trail horizontally. As it vines along the ground, it creates a canopy of dark green esthetically interspersed with its pastel flowers. Crown vetch generally stands upright at heights of one to two feet (0.3 to 0.6 metres), although stems reaching six feet (1.8 meters) in length also occur. Underground, its rhizomes, which sprout roots and shoots, may attain lengths of 10 feet (3.04 meters).

 

crown vetch seeds with seed pod

Provided by ARS Systematic Botany and Mycology Laboratory. Islamic Republic of Iran.
Provided by ARS Systematic Botany and Mycology Laboratory. Islamic Republic of Iran.

 

Because they are in the legume family, they produce seeds in pods, which are one to two inches (2.5 to 5 centimeters) in length. Seed pods, which are segmented, are borne as crown-like clusters. Seeds, which are numerous, have a cylindrical shape with a brownish color.

 

crown vetch pods

Gallagator Trail, Bozeman, Gallatin County, northwestern Montana
Gallagator Trail, Bozeman, Gallatin County, northwestern Montana

 

Crown vetch leaflets are lanceolate, meaning that, having the shape of a lance, their length exceeds their width. Their coloring is dark green.

Leaflets alternate and are odd-pinnate (imparipinnate), i.e., two rows of leaflets with a terminal leaflet. Leaflets may total anywhere from fifteen to twenty-five on a stem.

Crown vetch produces small half-inch (1.27 centimeters) flowers, colored pink and white or lavender-purple and white. Clustered on a stalk at the tips, flowers bloom from early in the spring to late in the autumn.

 

a sea of crown vetch

New Observatory Woods State Natural Area, Dane County, south central Wisconsin
New Observatory Woods State Natural Area, Dane County, south central Wisconsin

Horses: Clover slobber is preferred to Crown vetch paralysis

 

Whereas the Rhizoctonia leguminicola fungus, an extrinsic plant pathogen, is the culprit in equine slobberings after grazing on clover, nitroglycosides that are intrinsic to Securigera varia may:

  • retard growth in horses,
  • paralyze their hind quarters, or
  • even cause their death.

Nitroglycosides are plant toxins, of which coronarian is toxic to horses and other single-stomached (nonruminant) animals.

Coronarian inhibits succinate dehydrogenase, an enzyme that is critical for equine energy metabolism. Fatal toxicity occurs with the development of methemoglobinemia, wherein the horse’s blood is unable to carry oxygen to its tissues, producing abnormal levels of methemoglobin (oxygen-carrying protein hemoglobin with its iron in the ferric state) in the blood and tissue hypoxia (oxygen deprivation).

 

crown vetch: participant in lovely landscapes

Millennium Park, Kent County, west central Michigan
Millennium Park, Kent County, west central Michigan

Proliferation

 

Because of its rapid growth and spread, by both rhizomes and seeds, crown vetch effectively counters soil erosion in damaged soils. Crown vetch is not disturbed by eroded soil. As a member of the legume family Fabaceae, crown vetch establishes a symbiotic (Greek: sýn "with" and bíōsis “living”) relationship with rhizobia as its host plant. Rhizobia are soil bacteria that are classed as diazotrophs because they effectuate the essential process of nitrogen fixation. The process entails converting nitrogen gas, which they have extracted from the air, into a form of nitrogen that the host plant is able to use. As a result of this symbiotic relationship, crown vetch rehabilitates the soil content to acceptable levels for its survival.

The negative extreme of its easy proliferation is that Securigera varia quickly establishes control of areas, thereby banishing other desirable species. Its planting for purposes of erosion control along roadsides and rights-of-way and in open fields has provided crown vetch with a strong base of operations from which to spread. The hardy plant flourishes in poor soil, where there is little competition, and keeps extending its territory. Its seeds retain their viability in soil for several years, which increases not only their timeline for propagation but also their opportunities.

 

gentle pastel palette of crown vetch

Bodenheim, western Germany
Bodenheim, western Germany

Crown vetch invasion

 

Soon Securigera varia borders and then tackles gardens and lawns, weakening and oftentimes eliminating cultivated plants. As such, crown vetch is now considered to be an invasive species: their domination of their environment disrupts the habitat balance by adversely affecting the floral profile.

With this impairment in biodiversity, the ecosystem suffers imbalances and even abandonment. So a new kind of erosion -- the erosion from the plethora of polyculture to the paucity of monoculture  -- is established.

 

Distribution in Canada and the United States

 

Crown vetch, which is not native to the United States of Canada, has become naturalized extensively throughout these two North American countries.

In Canada, Securigera varia is found in all of the provinces. Although crown vetch has been reported on Newfoundland, it is not yet documented in Labrador. Crown vetch is not found in any of the three territories, so far.

In the United States, crown vetch has been documented in all states except Alaska and North Dakota. Securigera varia has been sighted in the nation’s capital, Washington, D.C. but it has not been reported in Puerto Rico nor has it been recorded in the U.S. Virgin Islands.

 

roadside crown vetch: planned plantings or infestation?

purple crown-vetch Securigera varia (L.) Lassen: following curve of highway guard rail
purple crown-vetch Securigera varia (L.) Lassen: following curve of highway guard rail

How to control Securigera varia

 

Control methods include

  • herbicides for large infestations
  • burning
  • manual removal, and
  • mechanical removal by mowing.

 

closeup of crown vetch flowers and foliage

Millennium Park, Kent County, west central Michigan
Millennium Park, Kent County, west central Michigan

Spring’s Securigera varia in my lawn

 

Purple crown vetch has made an impromptu appearance along the entire south side of my house. Specimens have also clustered around the west side of my house, to the south of the back stoop.

Moreover, purple crown vetch now arcs around the southwest curve of the ornamental rocks that bolster my house number at the opening into the eastern expanse of my yard. Situated a few feet from the road and from the entrance to my driveway, Securigera varia is readily visible to all passersby.

 

Chickory: Blue wild flower of Cichorium intybus

Lisbon, west central Portugal
Lisbon, west central Portugal

 

That welcome glimpse previously was proferred by chickory (Cichorium intybus), for which we fondly named my house Chickory Cottage. Chickory’s peaceful blue flowers blazed from a diminished number of plants last summer. Apparently crown vetch was already casting covetous rhizomes and seeds in the direction of the gentle chickories, which have beneficial uses, in addition to their loveliness, that have been enjoyed in the United States since their naturalization here in the 1700s.

The nightmare invasion by Securigera varia has been progressing with great determination, unbeknownst to me.

But now I know, and there is no way that my house is being renamed Vetch Cottage.

 

crown vetch's pleasing flower

closeup of crown vetch flower
closeup of crown vetch flower

Acknowledgment

 

My special thanks to:

  • Talented artists and photographers/concerned organizations who make their fine images available on the Internet;
  • Virginia Polytechnic Institute and State University for superior on-campus and on-line resources.

 

proliferation of healthy, verdant crown vetch leaves

closeup of leaves
closeup of leaves

Sources Consulted

 

Knight, Anthony P., and Richard G. Walter, eds. A Guide to Plant Poisoning of Animals in North America. Jackson WY: Teton NewMedia, 2001.

Panda, H. Handbook on Medicinal Herbs with Uses. Delhi, India: Asia Pacific Business Press, 2004.

USDA NRCS Plant Materials Program. "Crownvetch Coronilla varia L." USDA Plants Database > Plant Fact Sheet. February 1, 2002. United States Department of Agriculture Natural Resources Conservation Service. Web. plants.usda.gov

  • Available at: http://plants.usda.gov/factsheet/pdf/fs_cova2.pdf

 

closeup of crown vetch flower
closeup of crown vetch flower
the end which is also the beginning
the end which is also the beginning

Garden vetch (Vicia sativa): photo by Bob Gibbons

10x14 Photo Puzzle with 252 pieces. Packed in black cardboard box 5 5/8 x 7 5/8 x 1 1/5. Puzzle image 5x7 affixed to box top.
Photo Jigsaw Puzzle of Common Vetch - Ardea Wildlife Pets

Bithynian vetch (Vicia bithynica), Dorsetshire, South West England: photo by Bob Gibbons

10x14 Photo Puzzle with 252 pieces. Packed in black cardboard box 5 5/8 x 7 5/8 x 1 1/5. Puzzle image 5x7 affixed to box top.
Photo Jigsaw Puzzle - Ardea Wildlife Pets

Crown Vetch Flowers, a Barn, and a Vintage Truck Add Local Color: photo by Stephen St. John

Crown Vetch Flowers, a Barn, and a Vintage Truck Add Local Color

Me and my purrfectly purrfect Maine coon kittycat, Augusta "Gusty" Sunshine

Gusty and I thank you for reading this article and hope that our product selection interests you; Gusty Gus receives favorite treats from my commissions.
DerdriuMarriner, All Rights Reserved
DerdriuMarriner, All Rights Reserved
Updated: 08/20/2014, DerdriuMarriner
 
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DerdriuMarriner on 04/20/2014

Mira, The problem is that, as an invasive species, crown vetch takes over pastures; as they forage, horses are consuming them because the crown vetch slips in amidst pasture grasses.
Chicory root as a substitute for coffee was popular in America from colonial times all the way through the 20th century's Great Depression, after which it was replaced by coffee. I also like the flavor of chicory substitutes. It would make sense to me that chicory drinkers are able to work long hours: it's invigorating without the jittery effects sometimes associated with caffeine.
Chicory used to be well known in America as an edible, healthy plant. Now it seems that its culinary appeal is mainly appreciated in Europe. For instance, Belgian endive is in the chicory family.

Mira on 04/20/2014

They look beautiful, but it's amazing how harmful they can be. I'm particularly saddened to learn they are toxic to horses. Do horses know to stay away from them?
I love chickory. I recognize the flower but I wonder how come (I don't recall where I must have seen and learned about it.). I love instant chicory. Many people drank such beverages here under Communism. I don't know what they did for them caffeine-wise. On the other hand, maybe with the health benefits chicory has, they didn't need much coffee. Times were different, too. Not a whole lot of stress at work, even though (most) people did work, and some worked long hours.

DerdriuMarriner on 04/15/2014

VioletteRose, Me, too, I agree that the color combination of the petals is beautiful. And they look pretty in my yard, but they also scare away Chickory, so I weed them back so that, instead of the entire yard, they have a specific area.
Unfortunately non-native plants often become invasive as a survival mechanism as they adjust to unfamiliar environments.

VioletteRose on 04/15/2014

Beautiful combination of white and pink petals, I haven't seen these flowers anywhere. They are so pretty, it is unfortunate that their presence is a threat to other plants.

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