Native Plants

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Wednesday - August 20, 2008

From: Austin, TX
Region: Southwest
Topic: Non-Natives
Title: Viability of non-native Royal Poinciana in Austin
Answered by: Barbara Medford

QUESTION:

My question is about the tree called Royal Poinciana that grows so well in the Rio Grande Valley. I realise it isn't a native but hope you have an opinion about its chances of survival in Austin. I believe it is actually a Caesalpinia.

ANSWER:

The Delonix regia, Family Caesalpineaceae, is endemic to Madagascar, where it is endangered, but widely cultivated elsewhere. It is a tropical legume, related to the mimosa. One website we saw said it was hardy from Zone 10a to 11; another said 10b to 11, a pretty tight range of hardiness, and not representative of Austin! About the best you can hope for around here is Zones 7a to 8b. Information we found indicated that it would not grow well in a large pot in a greenhouse situation, and refused to bloom in a pot. If you are game to give it a try, it needs to be well-watered until established, then only during severe drought. You should not plant the tree closer than about 10 feet from a pavement or sidewalks, since large surface roots often grow beneath them and destroy them. This USDA Forest Service website on Royal Poinciana will give you more information.