One of the most distinctive features of redbuds, Cercis canadensis, the 2013 VNPS Wildflower of the Year, is its production of flowers on mature trunks and major branches, a habit termed cauliflory. Redbud flowers also form on young, one-year old twigs; as explained below, twig- and trunk-borne flowers are parts of a single developmental continuum; twigs bearing flowers eventually becoming trunks and large branches that continue to bear flowers.
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Hayden, W. John. "Redbud Cauliflory: The Inside Story." Bulletin of the Virginia Native Plant Society 32, no. 1 (Winter 2013): 1, 3, 8.