Ambrosia psilostachya

de Candolle in A. P. de Candolle and A. L. P. P. de Candolle

in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 526. 1836

Common names: Herbe à poux vivace
Synonyms: Ambrosia psilostachya var. californica (Rydberg) S. F. Blake Ambrosia psilostachya var. coronopifolia (Torrey & A. Gray) Farwell Ambrosia psilostachya var. lindheimeriana (Scheele) Blankinship Ambrosia rugelii unknown
Treatment appears in FNA Volume 21. Treatment on page 18. Mentioned on page 12, 15.
Perennials, 10–60(–100+) cm. Stems erect. Leaves proximally opposite, distally alternate; petioles 0–25 mm (often ± winged); blades deltate to lanceolate, 20–60(–140) × 8–35(–50+) mm, pinnately toothed to 1-pinnately lobed, bases cuneate to truncate, ultimate margins entire or toothed, abaxial and adaxial faces hirsutulous to strigose and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0.5–2 mm; involucres obliquely cup-shaped, 2–4(–5) mm diam., hirsutulous; florets 5–15(–30+). Burs: bodies ± obpyramidal to globose, 2–3 mm, hirsutulous, spines or tubercles 0 or 1–6, mostly distal, stoutly conic to acerose, (0.1–)0.5–1 mm, tips straight. 2n = 18, 27, 36, 45, 54, 63, 72, 100–104, 108, 144.

Phenology: Flowering Jul–Oct(–Dec).
Habitat: Disturbed sites, often wet, alkaline, clay soils
Elevation: 0–2200 m

Distribution

V21-25-distribution-map.gif

Alta., B.C., Man., N.S., Ont., P.E.I., Que., Sask., Ala., Ariz., Ark., Calif., Colo., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., La., Maine, Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Utah, Vt., Wash., Wis., Wyo., Mexico (Baja California, Chihuahua, Coahuila).

Discussion

Hybrids between Ambrosia psilostachya and A. artemisiifolia have been called A. ×intergradiens W. H. Wagner. Some botanists consider the type of A. cumanensis Kunth (1818) to be conspecific with that of A. psilostachya.

References

None.

Lower Taxa

No lower taxa listed.