Cirsium undulatum (Wavy-Leaved Thistle) - photos and description

 

 

 

 

 

 


Leaf side view in above photo.


Leaf side view in above photo.


Leaf side view in above photo.


Leaf topside in above photo.


Leaf topside in above photo.


Leaf underside in above photo.

General: Biennial or short-lived perennial thistle, very prickly. Stems stout, stems simple or branching near the top, plants usually with several stems from the caudex. Foliage is grey to white-woolly.

Flowers: Flower heads terminal and solitary on branches, pink in colour, with a slight scent. We measured flowers to 25 mm long and a flower head at 5.5 cm diameter and at 50 mm long (corolla + involucre). Involucre is very spiny.

Leaves: Leaves very prickly, reduced upwards, alternate, reduced in size upwards, linear-lanceolate. Leaves pinnately lobed, sometimes bifid, the lobes ovate and crowded together along the blade. Lobes generally greater than 7 mm wide - we measured lobes at 10 mm wide on 2nd year plants, and lobes at 20 mm wide on the leaves of 1st year rosettes.

Height: Height to 100 cm, we've measured plants to 74 cm tall.

Habitat: Dry prairies and roadsides in southern Saskatchewan.

Abundance: Fairly common.

Origin: Native.

Similar species:

This species is very similar to Cirsium flodmanii. To distinguish between the two:

- For C. flodmanii the uppermost lobe segment is at a near right angle to the blade of the leaf. The leaves of C. flodmanii are shiny green on top with slight pubescence and are white and very pubescent below. C. undulatum is sometimes called gray thistle because it has a white cast, with the top and bottom leaf surfaces very pubescent. The leaves of C. undulatum are less deeply lobed than C. flodmanii. C. undulatum is generally found in drier locations than those occupied by C. flodmanii. (The Thistles of North Dakota, Rodney G. Lym and Katheryn M. Christianson).

- Leaf lobes generally less than 7 mm wide for C. flodmanii, and generally greater than 7 mm wide for C. undulatum (Flora of Alberta).

- The lobes of C. flodmanii narrowly lanceolate, the ultimate leaf lobes of C. undulatum ovate-triangular (Common Plants of the Western Rangelands, Volume 3 Forbs).

The difference in the lobes of the leaves of the two species is shown below in the leaves of 1st year rosettes. The leaves of C. undulatum have ovate lobes (measured to 20 mm wide), crowded along the leaf blade. The leaves of C. flodmanii has linear to lanceolate lobes (measured to 5 mm wide), not crowded along the blade. 


C. undulatum - leaves of 1st year rosette, lobes ovate and crowded along the blade.


C. undulatum - leaves of 1st year rosette, lobes ovate and crowded along the blade.

C. flodmanii - leaves of 1st year rosette, lobes narrow and not crowded along blade.

When and where photographed: Photos taken August 12th, dry prairie pasture, Big Muddy, about 200 km south of our home in Regina, SK.