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American false mallow, Indian Valley false mallow

common false mallow, three-lobed false mallow, threelobe false mallow

Habit Herbs, perennial, or subshrubs, (0.5–)1–2 m, often bushy-branched in distal 1/2. Herbs, annual or perennial, 0.2–0.6(–1) m, with 1 main stem, freely branching in proximal 1/2.
Stems

erect, canescent, hairs tufted (not appressed), 6–8-rayed, infrequently glabrate.

erect or decumbent, hairs scattered, appressed, bilateral, (2–)4-rayed, swollen-based, not sublepidote, hairs 1–3 mm.

Leaves

stipules persistent, lanceolate, subfalcate, 3–5 × 1 mm, apex acuminate;

petioles 35–80 mm on proximal leaves, reduced to 10–15 mm on distal leaves and usually on xerophytes;

blade wide-ovate to ovate-lanceolate, very shallowly 3-lobed in distal 1/2 or unlobed (in most plants in the flora area), varying from 5–12 × 4–10 cm on proximal leaves to 2–4 × 1.5–3 cm on distal leaves, usually 1–2 times longer than wide, 2 times longer than petiole of proximal leaves to 3–5 times longer on distal leaves, base slightly cordate or rounded to truncate or cuneate, margins dentate to denticulate, apex acute, surfaces stellate-hairy, hairs (5–)6–12-rayed.

stipules persistent, lanceolate, subfalcate to falcate, 3–6 × 0.5–1 mm, apex acuminate;

petiole 10–20(–40) mm;

blade ovate to ± lanceolate, unlobed, (1.7–)3–4(–6.5) × (0.6–)1.5–3(–5.5) cm, 1.1–2.8 times longer than wide, 2.5–4.5 times longer than petiole, not greatly reduced on stem distally, base truncate to broadly-rounded to often wide-cuneate, margins dentate to serrate, apex acute, surfaces sparsely hairy, hairs bilateral, 2–4-rayed, stellate or with simple hairs on adaxial surface.

Inflorescences

first 1 or 2 flowers solitary, axillary, remainder in dense terminal spikes 3–10 cm, these terminating each branch;

floral bracts 2-fid, 4–5 × 2 mm.

axillary, solitary flowers, flowers sometimes congested towards branch tips;

floral bracts absent.

Pedicels

0.1–3 mm, not lengthening in fruit;

involucellar bractlets adnate basally to calyx for 1.5–2 mm, lanceolate, subfalcate, 5–7 × 0.8–1.5 mm, equaling to barely exceeding calyx lobes, apex acute to acuminate.

1–2 mm, to 3–5 mm in fruit;

involucellar bractlets basally adnate to calyx for 0.5–1 mm, lanceolate, subfalcate, 4–6 × 0.6–1 mm, shorter than calyx lobes, apex acute.

Flowers

calyx connate 1/4–1/3 its length, broadly campanulate, 5–6 mm, to 6–10 mm in fruit, surface densely hirsute, hairs scattered, appressed, apically directed, 1–1.5 mm, mixed with minute, closely appressed, 5–8-rayed, stellate hairs;

corolla wide-spreading, orange-yellow, 12–17 mm diam., petals obovate, shortly asymmetrically lobed, 6–10 × 4–6 mm, exceeding calyx by 2–3 mm;

staminal column 2–3 mm, stellate-puberulent;

style (9 or)10–15(–18)-branched.

Seeds

1.5 mm.

Schizocarps

4–6 mm diam.;

mericarps tardily shed from calyx, (9 or)10–15(–18), 1.5–3 × 1.5–2 × 0.8 mm, margins angled, sides radially ribbed, narrowly-notched, with 1 minute, proximal-apical mucro to 0.1 mm, minutely hirsute, hairs ascending, restricted to top, simple, 0.1–0.5 mm.

2n

= 24.

Malvastrum americanum

Malvastrum coromandelianum

Phenology Flowering nearly year-round when sufficiently wet and warm; frost-sensitive. Flowering spring–frost at northern limit as an annual (cold-sensitive), nearly year-round when sufficiently wet and warm as a perennial.
Habitat Open, usually secondary and disturbed habitats, near coast River floodplains and banks, disturbed areas, often in alkaline soil
Elevation 0–100 m (0–300 ft) 0–100 m (0–300 ft)
Distribution
from FNA
FL; TX; Mexico; Central America; West Indies; South America (to Argentina) [Introduced in Asia (China), Africa (Cape Verde Island), Pacific Islands (Indonesia), Australia]
[WildflowerSearch map]
[BONAP county map]
from FNA
FL; LA; TX; Mexico; Central America; West Indies; South America (to Argentina) [Introduced worldwide from Tropics and subtropics to warm temperate zones]
[WildflowerSearch map]
[BONAP county map]
Discussion

Plants of Malvastrum americanum from within the flora area tend to be shorter, and to have smaller, narrower unlobed leaves than those of the wet Tropics. The calyces and mericarps can attach easily to clothing and fur. The species is more cold-sensitive than M. coromandelianum and is not as widespread or weedy.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Malvastrum coromandelianum is a widespread weed and the most common species in the genus; it is apparently native from Texas to Argentina. The introduced and widespread form has simple hairs on the adaxial surface of the leaf, while the native form has stellate hairs on that surface. Both forms are found in Texas. The species historically has been introduced in ballast in Alabama, Massachusetts, Pennsylvania, and New Jersey, but did not persist.

Subspecies coromandelianum occurs in the flora area and is a widespread weed in tropical and warm-temperate areas worldwide; the other two subspecies occur only in South America and on the Galapagos Islands.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 6, p. 295. FNA vol. 6, p. 297.
Parent taxa Malvaceae > subfam. Malvoideae > Malvastrum Malvaceae > subfam. Malvoideae > Malvastrum
Sibling taxa
M. aurantiacum, M. bicuspidatum, M. corchorifolium, M. coromandelianum, M. hispidum
M. americanum, M. aurantiacum, M. bicuspidatum, M. corchorifolium, M. hispidum
Synonyms Malva americana, M. spicata, M. spicatum Malva coromandeliana, M. lindheimerianum
Name authority (Linnaeus) Torrey: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 38. (1859) (Linnaeus) Garcke: Bonplandia (Hanover) 5: 295. (1857)
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