Answer: It would be marginal in San Antonio. Royal poinciana is native to Madagascar. It is widely cultivated and may be seen adorning avenues, parks and estates in tropical cities throughout the world. Royal poinciana is very fast growing, about 5 ft (1.5 m) per year until maturity, and tolerant of a wide range of well drained soils from acidic to alkaline and from loamy to gravelly. It's best to provide protection from strong winds.
Royal poinciana is drought tolerant, but does best with regular water in the growing season and very little water in its dormant season.
Hardiness: USDA Zones 10 - 12. Royal poinciana should not be exposed to temperatures below about 45?F (7.2?C).
Propagation: Propagate royal poinciana from semi-ripe tip cuttings taken in summer. Best results come with bottom heat. Seedlings vary in flower characteristics and may take 10 or more years to flower.
Hope this information is helpful!
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