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Trifolium
pratense L.
Standardized Common
Name: Red
Clover
Other Common Name: Purple Clover
Family: Fabaceae
(Leguminosae)
Taxonomy: Trifolium
includes about 238 species, which are distributed almost worldwide except for
Australia. Trifolium pratense is
native to Eurasia and widely naturalized in North America. It is highly
variable, and nearly a dozen species-level synonyms exist; several dozen
varieties, races or forms have been described, many of which overlap in
features and are not clearly known to be natural entities. The authoritative
treatment of the genus reduces these to six varieties, of which the cultivated T. pratense var. sativum Schreb. in Sturm. is most commonly found in commerce.
Description: Perennial herb.
Stems numerous, erect (especially in var. sativum)
to ascending or nearly prostrate, 10–40 cm high (to 100 cm in var. sativum). Leaves trifoliolate, stipulate
with stipules fused to petiole; petioles long on lowest leaves, very short on
uppermost leaves; leaflets petiolulate, obovate to obovate-oblong or broadly
elliptical, 1.5–5 cm long, 0.7–1.5 cm broad, often spotted. Inflorescences
terminal heads, solitary or paired, globular to ovoid, subtended by a pair of
leaves. Flowers numerous, sessile, usually 1.5–1.8 cm long. Calyx tubular-campanulate,
10-nerved, usually pubescent, with 5 blunt teeth of which 4 are short and 1
long. Corolla bilaterally symmetrical, reddish-purple to pink, fading to brown
when dried, rarely whitish; petals 5, with 2 fused into a keel, 2 free wing
petals and 1 standard petal; standard longer than other petals, notched.
Stamens 10, 9 fused into a single group and 1 separate. Fruit a legume, ovate,
1-seeded, mostly membranous.
Parts
in Commerce:
Flowering heads
Identification:
- Inflorescence
a globular or ovoid head, not an umbel or spike
- Heads
not subtended by an involucre of bracts; stipules of uppermost pair of leaves
may be present
- Flowers
sessile, not on individual pedicels
- All
flowers with corollas and all or most fertile
- Flowers
mostly 1.5–1.8 cm long, not much smaller
- Calyx
with 10 nerves, not 5 or 15–20+
- Calyx
with 4 teeth equal in length, 1 much longer
- Calyx
teeth usually bristly or hairy, long and narrow but blunt-ended, not
sharp-pointed
- Calyx
with slight ring-shaped, hairy thickening, but thickening is not bilabiate or a
strongly callous ring
- Corolla
distinctly longer than the calyx, but extending less than a third of its length
beyond the longest calyx tooth
- Corolla
bilaterally symmetrical, 5-petaled
- Uppermost
or standard petal the largest, notched at apex; basal 2 petals fused into a
short keel
- Corolla
reddish-purple to pink, rarely whitish, often browning when dried
- Odor
fragrant
- Taste
weak, first sweet then bitter.
The
above characters together distinguish T. pratense from all other species
of Trifolium.
References:
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:439.
Zohary
M, Heller D. The Genus Trifolium.
Jerusalem: The Israel Academy of Sciences and Humanities; 1984.
Figure 77: a–c, Trifolium pratense inflorescence and
flower.
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