ASTERACEAE

SUNFLOWER FAMILY

David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.

XYLORHIZA

DESERT-ASTER

Perennial, subshrubs, shrubs
Stems generally white, glabrous or hairy
Leaves simple, alternate, entire or toothed; midrib white
Inflorescence: heads radiate, solitary, peduncled; involucre bell-shaped or hemispheric; phyllaries graduated in several series; receptacle convex, naked
Ray flowers generally many; corollas white to blue or purple
Disk flowers many; corolla yellow; style tips linear, acute
Fruit linear to club-shaped, weakly compressed, covered with long, appressed hairs; pappus of many, unequal bristles
Species in genus: 8 spp: w North America:
Etymology: (Greek: woody root)
Reference: [Watson 1977 Brittonia 29:199–216]

Native

X. tortifolia (Torr. & A. Gray) Greene var. tortifolia

MOJAVE-ASTER

Perennial, subshrubs 2–6 dm from much-branched caudex
Stems with long, non-glandular hairs and shorter, stalked glands
Leaves 2.5–10 cm, linear to lanceolate, oblanceolate or elliptic, generally soft-hairy and glandular, acute to spine-tipped, ± spiny-dentate, reduced upward
Inflorescence: peduncles 8–22 cm; phyllaries 5–25 mm, 0.7–2.5 mm wide, soft-hairy and glandular, innermost > or < immediately preceding series
Ray flowers 25–60; tube 4–6 mm; ligule 1–3.3 cm, light blue or white
Disk flowers 70–110; corolla 5.5–8.5 mm
Fruit 3–6 mm; pappus bristles < or = 9 mm
Chromosomes: 2n=12, 24
Ecology: Desert slopes, canyons
Elevation: 240–2000 m.
Bioregional distribution: s East of Sierra Nevada, Mojave Desert, n Sonoran Desert
Distribution outside California: to sw Utah, w Arizona
Flowering time: Mar–May, Oct
Synonyms: Machaeranthera t. (Torr. & A. Gray) Cronquist & D.D. Keck
Horticultural information: DRN, SUN: 2, 7, 8, 9, 10, 11, 12, 13, 18, 19, 20, 21, 22, 23, 24.