Slimleaf Sneezeweed

Annuals, 20–80 cm. Stems usually 1, branched distally, narrowly winged, sparsely hairy proximally, moderately hairy distally. Leaves glabrous or sparsely hairy (basal withered by flowering); proximal blades lance-linear, usually coarsely or irregularly laciniate; mid and distal blades lance-linear to linear, entire. Heads 5–50(–100+) per plant, in paniculiform arrays. Peduncles 2–8 cm, sparsely to moderately hairy. Involucres globose to slightly ovoid, 6–11(–13) × 6–11(–13) mm. Phyllaries moderately hairy. Ray florets 8–9, pistillate, fertile; corollas yellow throughout or red proximally and yellow distally or red throughout, 6–12 × 3–8 mm. Disc florets 150–300(–500+); corollas yellow-green proximally, brown to purple distally, 2.5–3.2 mm, lobes 5. Cypselae 1–1.2 mm, moderately hairy; pappi of 6(–7) entire, aristate scales 2–2.5 mm. 2n = 28.

Helenium linifolium Rydberg, sp. nov
A slender annual; stem about 3 dm. high, glabrous or nearly so, angled; leaves linear or narrowly linear-lanceolate, entire or sparingly dentate, rarely sinuately lobed, 4-6 cm. long, glabrous; heads corymbose; peduncles slender, 3-8 cm. long; involucral bracts 4-5 mm. long, lance-subulate; ray-flowers pistillate; ligules cuneate, 10-12 mm. long, 5-7 mm. wide, purplish with yellow tips, or yellow; disk purplish, 10-12 mm. broad; corollas about 2 mm. long, yellow with purple limb; tube very short; achenes 1 mm. long, hispid on the angles; squamellae ovate, with a long awn-tip, together fully three-fourths as long as the corolla.
Type collected at Kingsville, Texas, April 11, 1905, S. M. Tracy 8949 (herb. N. Y. Bot. Gard.). Distribution: Texas.

Helenium linifolium is a North American perennial plant in the sunflower family, commonly known as slimleaf sneezeweed. It is found only in southern Texas.

Helenium linifolium is an annual herb up to 80 cm (32 inches) tall, with wings running down the sides of the stems. Leaves are long and narrow, almost thread-like, merging with the wings on the stem. One plant can have 100 or more small spherical or egg-shaped flower heads. Each head has up to 500 disc flowers, each yellow-green toward the bottom but brown or purple toward the tip. There are also 8-9 red or yellow ray flowers.

Helenium linifolium là một loài thực vật có hoa trong họ Cúc. Loài này được Rydb. mô tả khoa học đầu tiên năm 1915.