Astragalus gilviflorus

Petasites sagittatus

Arrow-Leaved Colt's-Foot

Whole Plant (Staminate)

Good Spirit Lake Provincial Park
14-May-2010

Note the large number of inner tubular florets surrounded by a small number of peripheral ray florets in each flower head. Note also that some authors consider the cauline leaves to be merely bracts, thus implying that all the leaves are basal.

This plant is imperfectly dioecious and the flower head morphology is complicated. The following is a summary of the rather dense description in the Flora of North America entry for Petasites.

Staminate flower heads are usually composed of a small number of peripheral ray florets that are either neuter or style-bearing and sterile, and a large number of inner tubular florets that are functionally staminate. (The neuter florets have a reduced, sterile style or no style at all.)

Pistillate flower heads are usually composed of a large number of peripheral ray florets that are functionally pistillate, and a small of number of inner tubular florets that are functionally staminate. In between the two sets there may be a number of intermediate florets that are functionally pistillate and whose corolla ranges from five-lobed to minutely two-lipped to bearing a reduced ligule.

There can be deviations from the above. Ray florets are occasionally missing from both staminate and pistillate heads. The inner tubular florets of staminate heads are occasionally bisexual and fertile. Finally, Flora of the Great Plains states that the peripheral ray florets of staminate heads can be functionally pistillate.

Interestingly, this complicated reproductive morphology varies little between the various putative species recognized by Budd's Flora, Flora of Alberta and this site. Species are therefore differentiated based upon leaf character states. Flora of North America finds that there is intergradation between all these states, and as a result includes all these species as varieties under a single P. frigidus.

Note that one of the paths to Petasites in the Budd's Flora key incorrectly requires florets yellow or greenish yellow; NOT [florets purplish white, purple, or rose]. The rest of the key answers are listed below.

Sagittatus: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.

leaves cordate to triangular; NOT [leaves round, kidney-shaped, or triangular]

leaves nearly entire or merely dentate; NOT [leaves deeply lobed]

pappus generally more than 15 mm long; NOT [pappus 15 mm long or less]

Petasites: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus.

herbs; NOT [low grayish shrubs]

juice watery; NOT [juice milky]

leaves alternate or basal; NOT [most of the leaves opposite]

leaves all basal

basal leaves cordate or sagittate; NOT [basal leaves, if any, not cordate or sagittate]

basal leaves felty-pubescent

basal leaves appearing after the flowers; NOT [basal leaves appearing before the flowers]

leaves without spiny-tipped teeth

bracts of involucre not dry or parchmenty, usually green; NOT [bracts of involucre dry, parchmenty or membranous, not green]

involucral bracts not spiny tipped and without hooked bristles; NOT [involucral bracts spiny-tipped or with hooked bristles]

receptacle naked; NOT [receptacle densely bristly]

some or all of the florets tubular

ray florets conspicuous

ray florets whitish

flowers of some heads all pistillate or the outer flowers pistillate; NOT [flowers all perfect]

stamens united to form a tube around the pistil

pappus present, distinct; NOT [pappus none or inconspicuous]

pappus of numerous capillary bristles, sometimes plumose; NOT [pappus of a few hairs, of scales, or of awns, or a crown or none]

NOT [basal leaves mostly 1-6 cm long, linear to oblanceolate or spatulate, forming a dense rosette; plants with a well-developed taproot; and either densely caespitose, seldom more than 5 cm tall, the heads sessile among the leaves, or with stout, simple stems, 5-15 (25) cm tall, heads solitary, involucres 2-4 cm wide, bracts ciliate to pectinate or fimbriate, rays blue and achenes densely pubescent, obovate to triangular]