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Published In: Genera Plantarum 129. 1789. (Gen. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/18/2017)
Acceptance : Accepted

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. Phacelia Juss. (scorpionweed, phacelia)

Plants annual or biennial (perennial elsewhere), with slender taproots (sometimes stouter in P. bipinnatifida). Stems loosely to strongly ascending, sometimes from a spreading base, variously pubescent, at least in part with stiff, straight, spreading to downward-angled, somewhat pustular-based hairs, in some species nearly glabrous with age. Basal leaves usually present (in some species the oval, unlobed cotyledons also persistent) but often withered at flowering, usually relatively small (the blade usually less than 7 cm long, except in P. bipinnatifida), long-petiolate, the blade pinnately lobed or compound, the upper surface usually not mottled. Stem leaves alternate, long-petiolate to sessile, variously hairy. Leaf blades variously shaped, moderately to deeply pinnately lobed or compound (entire elsewhere); the pinnae or lobes narrowly rounded to more commonly bluntly or sharply pointed at the tip, the margins otherwise entire to deeply lobed, the surfaces variously hairy. Inflorescences initially sometimes compact, continuing to elongate during the flowering season (except occasionally in P. covillei and P. ranunculacea), consisting of solitary or less commonly paired open racemes with the flowers often mostly oriented along 1 side, often somewhat congested and scorpioid at the tip, the flower stalks 3–14 mm long at flowering, becoming elongated at fruiting, variously hairy. Calyces becoming somewhat enlarged at fruiting, lacking appendages, the lobes narrowly triangular to narrowly lanceolate (sometimes becoming slightly broader at fruiting), sharply pointed at the tip, the surfaces and margins variously hairy. Corollas narrowly to broadly bell-shaped (sometimes nearly cylindrical in P. covilleii and P. ranunculacea), white or lavender- or bluish-tinged. Stamens exserted or not, the filaments attached at or near the base of the corolla tube, glabrous or hairy, with a small linear gland between each pair of adjacent filament bases, this usually fused along all or most of its length with a minute pair of appendages or ridges. Ovary incompletely (sometimes nearly completely) 2-locular, the placenta-bearing portions of the wall intruding into the locule as a partition. Style exserted or not, shallowly or deeply branched. Fruits (2–)3–6 mm long, more or less globose, moderately to densely hairy toward the tip, at least when young, 2–8-seeded. Seeds 1.5–3.0 mm long, ovoid with a longitudinal line or ridge along the inner side to nearly globose, the surface with a network of ridges or occasionally appearing pitted, brown or black. One hundred fifty to 200 species, North America, Central America.

The Missouri species of this genus have all been classified as members of subgenus Cosmanthus (Nolte ex A. DC.) Constance, a group of about 15 species that is most diverse in the eastern half of the United States (Constance, 1949b). However, more taxonomic research is necessary to test whether the subdivision of the genus into three subgeneric groups based primarily on cytological patterns and annual vs. perennial habits reflects actual affinities (Sewell and Vincent, 2006).

Some species of Phacelia cause dermatitis in a few individuals when handled, but this may be due to the stiff sharply pointed hairs rather than because of reaction to some caustic chemical exudate. The genus contains a number of species considered good bee plants for the production of honey.

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