crown vetch

Crown vetch is a perennial forb that rises from a woody base (caudex), a taproot, and underground stems (rhizomes). The taproot is deep and multiply branched. The rhizomes are fleshy, branched, and up to 10′ long or longer. In their vegetative state plants are usually no more than 12″ tall. When in flower they may be up to 36″ tall. They often form dense tangled mats or mounds, and often large dense colonies that crowd out native plants and limit the establishment of shrubs and trees.

The stems are spreading to ascending, 12″ to 48″ long, and branched. They are angled or ridged and hairless or sparsely covered with spreading hairs. They do not have thorns.

The leaves are alternate, 2″ to 6″ long, and stalkless or almost stalkless. They are pinnately divided into 9 to 25 leaflets—4 to 12 pairs of lateral leaflets and a terminal leaflet. They do not have tendrils. At the base of each compound leaf there is a pair of small, leaf-like appendages (stipules). The stipules are green, narrowly lance-shaped to narrowly oblong or oblong triangular, and 1 ⁄32″ to ⅛″ long, much smaller than the leaves. They are always completely free of each other, not joined. Older stipules have a dark tip caused by an aggregation of tannin cells.

The leaflets are oblong to inversely lance-shaped, ¼″ to 1″ long, and ⅛″ to ⅜″ wide. They are rounded or angled at the base rounded, bluntly pointed, or squared off at the tip, with a minute, sharp point at the tip. The upper surface is green and hairless and usually has dark purple dots (glands) that are visible only with magnification. The lower surface is hairless purplish tinged or mottled. The margins are untoothed.

The inflorescence is a spreading, crown-shaped, umbrella-like cluster (umbel) of 5 to 20, usually 10 to 15, flowers rising from upper leaf axils. The stalk of the umbel is 2″ to 6″ long and angled. Each flower is on a ⅛″ to ¼″ long stalk (pedicel). Each pedicel is subtended by a single 1 ⁄64″to 1 ⁄32″ long modified leaf (bract). The bracts are free, not joined, and have dark tips.

The individual flowers are ⅜″ to ½″ long. There are 5 sepals, 5 petals, 10 stamens, and 1 style. The sepals are green and are fused for most of their length into a 1⁄32″ to 1 ⁄16″long long, hairless, bell-shaped calyx tube. The 5 petals form a butterfly-like corolla typical of plants in the Pea family. Each of the petals is abruptly narrowed (clawed) at the base. They are organized into a broad banner petal at the top, two lateral wing petals, and between the wings two petals fused into a keel. The banner is pink or purplish-pink and sometimes has a darker raised ridge in the center. It is abruptly arched upright from below the middle. The expanded portion is broadly egg-shaped, ⅜″ to ½″ long, and 3 ⁄16″to 5 ⁄16″ wide. The wings are ⅜″ to ⅝″ long and ⅛″ to 3 ⁄16″ wide. They are also pink but are noticeably paler than the banner, sometimes nearly white. The keel is purple, boat shaped, ⅜″ to ½″ long, and 1 ⁄16″ to ⅛″ wide. Nine of the filaments are long and their filaments are fused. The remaining filament is shorter and is free. The anthers are yellow. The style is slender, 3 ⁄16″ to ¼″ long, and curved upwards.

The fruit is a bluntly 4-angled, ¾″ to 2⅜″ long seedpod containing 3 to 12 seeds. It is green at first, becoming straw-colored or tan, then eventually brown when ripe. It is not flattened and is only slightly constricted between the seeds. When it ripens it breaks into one-seeded segments.

Spreading; 12″ to 24″ tall

Pink

When in flower there is no similar species. In its vegetative state it appears similar to species in the Vicia and Lathyrus genera. Securigera is distinguished by the absence of tendrils; a terminal leaflet; an umbrella-like inflorescence; and fruits that break into one-seeded segments at maturity. Crown vetch is the only species of Securigera that is found in Minnesota.

Moist to moderate moisture. Highway embankments, roadsides, railroads, drainage ditches, meadows, savannas, pastures, old fields, and other disturbed sites. Full or partial sun.

May to September

Crown vetch has been planted extensively since the 1950s on highway embankments in the upper two thirds of the United States to prevent erosion. The practice is now discouraged because its dense colonies often hide rather then prevent soil erosion. It has been used since the 1970s to revegetate abandoned mining sites. It has been and still is planted in gardens as an ornamental. It readily escapes cultivation. Once established, it takes a combination of methods and several years to eradicate.

Sources

2, 3, 4, 5, 7, 22, 24, 28, 29, 30.

Native to Western Asia and Europe. Introduced in North America in 1869 or earlier and naturalized.

Widespread; common in the Midwest, including Minnesota.

The genus Securigera was split off from the genus Coronilla in 1989 (Lassen) based on morphological characteristics. Preliminary DNA analysis done in 2000 and 2003 support the segregation.

Plant

Inflorescence

Inflorescence

Environmental Laboratory - U.S. Army Corps of Engineers
EnvLabERDC

Cieciorka pstra
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Crown Vetch Control Using Foam Herbicide for Precision Applications
Green Shoots

Garden Design & Care : Growing Crown Vetch
ehowgarden

Location: Spring Lake Park Reserve

Crown Vetch at Spring Lake Park Reserve. Unfortunately, it's becoming more and more prevalent in the unmowed areas.

Location: Joy Park & Preserve in Maplewood, MN