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]

LARREA

CREOSOTE BUSH

Shrub, unarmed
Stem branched, erect to prostrate, < 4 m, reddish becoming gray; nodes swollen, darker; hairs 0 or appressed
Leaf: stipules persistent; leaflets 2, fused at base
Inflorescence: flowers solitary in axils
Flower: sepals deciduous, unequal, overlapping; petals clawed, twisted, propeller-like, yellow, deciduous; stamen appendages bract-like, coarsely toothed
Fruit 5-lobed, spheric, short-stalked, hairy, splitting into 5 hairy, 1-seeded nutlets
Species in genus: 5 species: warm, dry Am
Etymology: (J.A. Hernandez de Larrea, Spanish clergyman)

Native

L. tridentata (DC.) Coville

Leaf: leaflets < 18 mm, < 8.5 mm wide, obliquely lanceolate to curved; deciduous awn between leaflets < 2 mm
Flower < 2.5 cm wide; sepals ovoid, appressed-hairy; petal claw brownish; stamens > appendages; ovary hairs dense, straight, stiff, silvery (reddish brown in fruit); style 4–6 mm, persistent on young fruit
Fruit 4.5 mm wide
Ecology: Common. Desert scrub
Elevation: < 1000 m.
Bioregional distribution: East of Sierra Nevada, Desert, (uncommon in Tehachapi Mountain Area, San Joaquin Valley, South Coast, San Jacinto Mountains)
Distribution outside California: to sw Utah, Texas, c Mexico
Flowering time: Apr–May
Synonyms: var. arenaria L.D. Benson, Algodones creosote bush; L. divaricata subsp. t. (DC.) Lowe & Felger
Closely related to s South America L. d. Clones may live 10,000 years, longer than any other living plants known; resinous odor characteristic; dominant shrub over vast areas of desert
Horticultural information: DRN, SUN: 7, 8, 9, 10, 14, 18, 19, 20, 21, 22, 23 &IRR: 11, 12, 13; also STBL.