200506 Northern Catalpa tree (Catalpa
speciosa) - USDA Illustration
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USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. Illustrated flora
of the northern states and Canada. Vol. 3.
USDA, NRCS. 2012. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.