Helianthus maximilianii

Narrow-leaved Sunflower

G.F. Ledingham Herbarium

Flora of Alberta states that the achenes of genus Helianthus bear a "pappus of small scales or awns, soon falling off".

Budd's Flora keys genus Helianthus as having "achenes without barbed awns" (italics my own).

It also keys genus Helianthus as having "pappus composed of scales, bristles, or barbs"; not "pappus absent, or present merely as a short crown".

I have found that neither flora easily distinguishes between Helianthus and Rudbeckia (Rudbeckia hirta is Black-eyed Susan) in their keys.  However, they do note that the receptacles of Rudbeckia are more conic and the leaves always alternate.

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Maximilianii Characteristics
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perennials

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rootstocks not tuber-bearing

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stem conspicuously pubescent below the inflorescence with short white hairs

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leaves mostly opposite

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leaves generally lanceolate or linear lanceolate

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leaves generally folded lengthwise

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leaves rough on both sides

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involucre bracts narrow, mostly with loose acuminate tips

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involucre bracts covered with short white hairs, sometimes ciliate toward the base

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disk yellow or light brown

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receptacle convex or low conical

 

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Helianthus Characteristics
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juice watery, not milky

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plants not heavy scented

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plants more or less leafy-stemmed

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plants not with a woody caudex

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leaves not compound

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leaves not linear

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at least the lower leaves opposite

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involucre not glandular nor glutinous

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involucre bracts in one or more series, but all of the same nature

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receptacle flat or convex, not conic or columnar

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receptacle with chaffy scales between the florets

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flower heads with both tubular and ray florets

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rays conspicuous

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ray florets yellow

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ligulate (ray) flowers either pistillate or neutral

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pappus composed of small scales or awns, soon falling off; not composed of hairs