Canadian tick-trefoil

(Desmodium canadense)

               
Conservation Status

IUCN Red List

not yet assessed

Canadian tick-trefoil

NatureServe

N5? - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FAC - Facultative

Midwest

FACU - Facultative upland

Northcentral & Northeast

FAC - Facultative

Nativity

Native

 
Occurrence

Common

 
Habitat

Moist to wet. Thickets, riverbanks, streambanks.

 
Flowering

July to August

     
Flower Color

Purple to pink

     
Height 36 to 72      

Identification

This is a 36 to 72 tall, erect, perennial forb that rises from a long, slender taproot. It often forms colonies.

The stems are erect or strongly ascending. They are usually unbranched below the inflorescence and branched within the inflorescence. They are covered with minute, short, white, hooked hairs and longer, soft, white, spreading hairs, at least near the top.

The leaves are alternate and are pinnately divided into 3 leaflets. They are on leaf stalks (petioles) that are up to 1 long near the base of the plant, becoming shorter as they ascend the stem. Upper leaves are nearly stalkless. At the base of each compound leaf is a pair of leaf-like appendages (stipules). The stipules are linear awl-shaped, 3 16 to 5 16 long, and finely hairy.

The terminal leaflet of mid-stem leaves is oblong or lance-shaped, 2 to 3½ long, up to wide, and on a relatively long leaflet stalk (petiolule). The blade is more than 4 times as long as it is wide and is much longer than the petiole and petiolule together. It is symmetrical, rounded at the base, and angled or short-pointed at the tip. The upper surface is green and is covered with minute, fine, hooked hairs and longer, soft, appressed hairs. The lower surface is paler green and is covered with soft, appressed hairs but does not have hooked hairs. The margins are untoothed and are fringed with minute hairs. The lateral leaflets are similar but smaller, asymmetrical, and on very short petiolules.

The inflorescence is a branched array (panicle) of densely-flowered, 8 to 12 long, unbranched, spike-like clusters (racemes) of numerous flowers at the end of the stem. The racemes are subtended by small but conspicuous leaf-like appendages (bracts). The bracts are lance-shaped to egg-shaped and to 7 16 long. They are conspicuous at flowering time but soon fall off.

Each flower is to ½ across measured vertically and is attached to the central axis by a hairy, red, 3 16 to 5 16 long stalk (pedicel). There are 5 greenish sepals (calyx) fused at the base into a short, 3 16 to ¼ long, hairy tube, then separated into 2 lips.

The 5 petals are reddish-pink or bluish-purple, becoming dark blue when they wilt. They form a butterfly-like corolla, typical of plants in the Pea family. They are organized into a banner petal at the top, 2 lateral wing petals, and between the wings 2 petals fused into a keel. The banner is divided into 2 lobes that are fused for most of their length, making the banner appear notched at the tip. It has 2 purple-rimmed yellow spots near the base. There are 10 stamens, 9 of them fused together forming a sheath around the pistil, the uppermost 1 free. There is no floral scent.

The flowers produce no nectar. They are pollinated by large, pollen collecting bees. Before pollination the banner is strongly bent backward near the base, the lobes rising vertically; the lateral wings covering the keel; and the wing-covered keel held nearly straight, parallel to the ground. After landing on a flower a bee forces wings apart and away from the banner. This causes the keel to snap downward violently releasing the column with an explosion of pollen.

The fruit is a flat, slightly curved pod (loment) on a 1 16 to long stalk. It is about 1 long and is divided into 3 to 5 triangular segments. When ripe the segments separate into single-seeded, 3 16 to ¼ long joints (articles). The articles have an almost straight upper margin, a rounded lower margin, and a dense covering of hooked hairs. They are spread by clinging to the fur of passing animals and to the jeans and socks of passing hikers.

 
Similar
Species

Hoary tick-trefoil (Desmodium canescens) petioles are much longer, nearly as long as the terminal leaflet. The flowers are slightly smaller, about long.

Illinois tick-trefoil (Desmodium illinoense) petioles are much longer, 2 to 3½ long. The stipules egg-shaped, not lance-shaped; are broader; and are twice as long, to long. The lower surface of the leaflet has hooked hairs. The flowers are pale purple or white and are slightly smaller, 5 16 to long. The pedicels are longer, ½ to long. There are usually only a few flowers in bloom at any one time. The loment has 2 to 5 segments that are well rounded on both the upper and lower margins. The articles are round or oval, not triangular.

Pointed-leaved tick-trefoil (Desmodium glutinosum) leaves are grouped near the middle of the stem, appearing whorled.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 28.

Comments

 


Taxonomy

Family:

Fabaceae (pea)

 

Subfamily:

Faboideae (Papilionoideae)

 

Tribe:

Desmodieae

 

Subtribe:

Desmodiinae

 
Synonyms

Meibomia canadensis

 
Common
Names

Canada tickclover

Canadian tick-trefoil

showy tick-trefoil

showy ticktrefoil


 

 

 

 

 

 

 

 

Glossary

bract

Modified leaf at the base of a flower stalk or flower cluster.

 

compound leaf

A leaf that is divided into leaflets, each leaflet having the general appearance of a leaf, with all leaflets attached to a single leaf stem.

 

loment

A seedpod that is constricted between the seeds and breaks apart into one-seeded segments when mature.

 

panicle

A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.

 

pedicel

In plants: the stalk of a single flower in a cluster of flowers. In Hymenoptera and Araneae: the narrow stalk connecting the thorax to the abdomen.

 

petiole

The stalk of a leaf blade or compound leaf that attaches the leaf blade to the stem.

 

petiolule

The stalk of a leaflet blade on a compound leaf.

 

pinnate

Having the leaflets of a compound leaf arranged on opposite sides of a common stalk.

 

raceme

An unbranched, elongated inflorescence with stalked flowers. The flowers mature from the bottom up.

 

stipule

A small, leaf-like, scale-like, glandular, or rarely spiny appendage found at the base of a leaf stalk, usually occurring in pairs and usually dropping soon.

       

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Colony

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Plant

  Canadian tick-trefoil   Canadian tick-trefoil
       
  Canadian tick-trefoil   Canadian tick-trefoil
       

Inflorescence

  Canadian tick-trefoil   Canadian tick-trefoil
       

Flowers

  Canadian tick-trefoil   Canadian tick-trefoil
       
  Canadian tick-trefoil   Canadian tick-trefoil
       

Leaves

  Canadian tick-trefoil   Canadian tick-trefoil
       
  Canadian tick-trefoil   Canadian tick-trefoil
       

Stem

  Canadian tick-trefoil    
       

Fruit

  Canadian tick-trefoil    
       
       

 

Camera

     

Slideshows

   
  Desmodium canadense SHOWY TICK TREFOIL
Frank Mayfield
 
  Desmodium canadense SHOWY TICK TREFOIL  

 

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Other Videos

 
  Showy Tick Trefoil - Desmodium canadense blooming at Ion Exchange, inc.
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Uploaded on Aug 1, 2011

Earthyman views Showy Tick Trefoil (Desmodium canadense) blooming at Ion Exchange in Northeast Iowa. http://www.ionxchange.com

 
     

 

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