Cascara buckthorn
Frangula purshiana · Rhamnaceae
Cascara buckthorn (Frangula purshiana) is a perennial tree in the Rhamnaceae family. It is native to North America. USDA records it as hardy in zone 6 and warmer, down to about -3°F.
At a glance
| Type | tree Derived |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 35 ft USDA |
| Light | shade USDA |
| Water need | medium USDA |
| Growth rate | slow USDA |
| Soil pH | 5.9–7.9 USDA |
| Bloom | April–May USDA |
| Flower color | White USDA |
| Hardiness zones | 6 and warmer USDA |
| Guild layer | understory Derived |
| Nursery availability | No Known Source USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It tolerates full shade. USDA rates it as having moderate water needs. Its drought tolerance is rated medium. It will not tolerate waterlogged soil — USDA rates its anaerobic tolerance as none. It is recorded on soils from pH 5.9 to 7.9 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 6.
Size and growth
At maturity it reaches about 35 ft, making it a substantial woody plant. It grows slowly.
Bloom period
USDA records a bloom period of April through May. Flowers are white.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is dark green, coarse in texture. Its flowers are not conspicuous — a plant for form and foliage. It carries conspicuous autumn colour. Its fruit or seed heads are conspicuous, extending interest past flowering. Its active growth period is spring and summer. USDA rates its lifespan as long.
What the site needs to provide
USDA records it across sites receiving 14 to 45 inches of annual precipitation. The low end of that band is genuinely arid, so it has a wide tolerance for dry country. It needs at least 150 frost-free days to finish its season. It roots to at least 24 inches. Fertility requirement: low — no feeding needed on ordinary garden soil.
Propagating it
It takes readily from seed, cuttings, bare root and container stock. Seed needs cold stratification — a period of moist chilling — before it will germinate, so sow in autumn or chill it artificially before a spring sowing. Its seed spreads at a slow rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Its fire tolerance is rated medium, and it can resprout after damage. Its growth form is recorded as multiple stem.
Role in a guild
Understory. In a layered planting this is the layer beneath the canopy, tall enough to hold structure but shaded from above. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Frangula
- glossy buckthorn Frangula alnus
- beechleaf frangula Frangula betulifolia
- Carolina buckthorn Frangula caroliniana
- California buckthorn Frangula californica
Similar role and hardiness
- Uruguayan pampas grass Cortaderia selloana
- parsley hawthorn Crataegus marshallii
- Franklin tree Franklinia alatamaha
- little walnut Juglans microcarpa
- crapemyrtle Lagerstroemia indica
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol FRPU7, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, Bloom, Bloom end, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, lifespan, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer, Type.
Read our full data sources and methodology.
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