7.
Boerhavia erecta
Linnaeus, Sp. Pl. 1: 3. 1753.
Erect spiderling
Herbs,
annual [slightly woody at base]; taproot tapered, soft or ± woody.
Stems
usually erect, sometimes decumbent, profusely branched primarily distally, 2-12 dm, minutely puberulent with bent hairs basally, usually glabrous, rarely sparsely puberulent distally.
Leaves
mostly in basal
1
/2 of plant; larger leaves with petiole 6-40(-55) mm, blade broadly rhombic-ovate, triangular-ovate, ovate, oval, or lanceolate, 20-50(-80) × 10-45 mm (distal leaves smaller, proportionately narrower), adaxial surface usually glabrous, sometimes minutely puberulent, usually minutely punctate, abaxial surface slightly paler than adaxial, usually glabrous, sometimes minutely puberulent, usually punctate with small patches of small brown cells, base obtuse to round, margins entire or sinuate, apex usually acute, less often obtuse or rounded.
Inflorescences
terminal, forked ca. 4-6 times ± evenly, diffuse, usually with sticky internodal bands; branches strongly ascending, terminating in irregular umbellate or subracemose clusters of flowers, not all pedicels attaching at same point (flowers occasionally borne singly).
Flowers:
pedicel (0-)0.3-2.5(-5) mm; bracts at base of perianth deciduous, usually 2, narrowly to broadly lanceolate, 0.5-1 mm, apex often acuminate; perianth whitish, usually tinged with pink or purple [bright pink] between lobes and in tube, campanulate beyond constriction, 1-1.5 mm; stamens 2-4, slightly exserted.
Fruits
1-11 per cluster, pale greenish to straw colored or tan, narrowly obconic, (2.7-)3-3.5[-4] × 1.2-1.5 mm (l/w: (2-)2.3-3.2), apex truncate or broadly low conic, glabrous; ribs 5, acute, slightly rugose adjacent to sulci; sulci 0.5-1 times as wide as base of ribs, slightly to prominently coarsely transverse rugose, not papillate.
Flowering early summer-mid fall. Disturbed areas, gardens, road and railroad rights-of-way, stream beds; 0-1700 m [probably much higher in tropics]; Ala., Ariz., Ark., Fla., Ga., La., Md., Miss., Mo., N.Mex., N.C., Okla., S.C., Tenn., Tex.; Mexico; West Indies; Central America; South America; widely introduced throughout the tropics and warm-temperate regions.
Boerhavia erecta
occasionally forms mixed populations with
B. intermedia
without apparent intergradation. Rarely, some specimens seem to combine features of either species, particularly with regard to inflorescence structure. This is especially so in Sonora, Mexico, and in parts of the Sonoran Desert in Arizona. The two species bloom simultaneously and are visited by small insects. Given the presumed close relationship and weedy habitats of each, hybridization seems possible. Usually, the two species can be distinguished by the differences in fruit length, the appearance of a crownlike apex of the nearly mature fruits of
B. erecta
(apex of ridges slightly expanded, apex of fruit slightly conic), and the more precisely constructed terminal umbels of
B. intermedia
. Both species, particularly
B. intermedia
, may produce entire inflorescences with branches terminating in single flowers. R. E. Woodson Jr. and H. J. Kidd (1961) suggested that
B. erecta
hybridizes with the perennial
B. diffusa
.
