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ZYGOPHYLLACEAE

CALTROP FAMILY

Duncan M. Porter

Herb, shrub, often armed; caudex present or not
Stem branched; nodes often angled, swollen
Leaves 1-compound, opposite; stipules persistent or deciduous; leaflets entire
Inflorescence: flowers 1–2 in axils
Flower bisexual; sepals 5, free, persistent or deciduous; petals 5, free, generally spreading, sometimes twisted and appearing propeller-like; stamens 10, sometimes appendaged on inside base; ovary superior, chambers 5–10, ovules 1–several per chamber, placentas axile
Fruit: capsule or splitting into 5–10 nutlets
Genera in family: 26 genera, ± 250 species: widespread especially in warm, dry regions; some cultivated (Guaiacum, lignum vitae; Peganum, harmal (NOXIOUS and illegal); Tribulus, caltrop (pernicious)). Peganum harmala L. has been reported as a pernicious weed near Daggett, San Bernardino Co
Reference: [Porter 1972 J Arnold Arbor 53:531–552]

TRIBULUS

PUNCTURE VINE, CALTROP

Annual
Stem prostrate, spreading radially, < 1 m
Leaf even-1-pinnate; stipules ± leaf-like
Inflorescence: flowers solitary in axils
Flower: sepals deciduous; petals yellow, deciduous
Fruit 5-lobed, splitting into 5 nutlets, each with 2–4 stout spines; style deciduous; peduncle reflexed
Seeds 3–5 per chamber
Species in genus: ± 12 species: especially dry Africa
Etymology: (Greek: caltrop, weapon used to impede cavalry, from armed fruit)

Introduced

T. terrestris L.


Stem ± silky or appressed-hairy, sharply bristly to glabrous
Leaf: stipules 1–5 mm; leaflets 6–12
Flower < 5 mm wide; peduncle < subtending leaf
Fruit 5 mm, < 1 cm wide, ± flat, hairy, gray or yellowish; spines 4–7 mm, spreading, hairy to glabrous
Ecology: Roadsides, railways, vacant lots, other dry, disturbed areas
Elevation: generally < 1000 m.
Bioregional distribution: California
Distribution outside California: to Wyoming, e US, c Mexico; native to Mediterranean
Flowering time: Apr–Oct
First collected in CA in 1902; long a pernicious weed, now controlled by introduced weevils. TOXIC to livestock in vegetative condition, fruits cause mechanical injury.

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