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Oregon State Landscape Plants lists Heteromeles arbutifolia as hardy to USDA Zone 7, usually reaching 15-20 feet (4.5-6 m) high in full sun or very light shade, needing good drainage and infrequent summer water; horticultural sources put its comfortable upper range at the warm end (zone 11), so Plotwright records the published floor and the warm-climate ceiling as 7a-11b.
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The Lady Bird Johnson Wildflower Center documents it as native only to California (CA) — semi-dry brushy slopes, foothills, and canyons below 4000 ft, extending into Baja California — and as adaptable, long-lived, and drought-tolerant on poor, dry, well-drained soil; it tolerates serpentine soil and exhibits allelopathic tendencies.
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Plotwright Heat Tier Warm-Extreme per ADR 0021 — a Mediterranean-climate chaparral shrub adapted to hot, dry California summers with no supplemental water once established, while the Zone-7 hardiness floor lets it persist through cooler inland winters.