One of the few “photographic regrets” I had from my recent trip to California was not stopping to photograph the flowering Cercis occidentalis in Shasta-Trinity National Forest of northern California. I was too intent on my destination, so instead I’ve added it to the ever-increasing list of places to revisit. Sandy’s photograph brings back some pleasant memories, so I appreciate that. I also have to add that one of my favourite Eliot Porter photographs is Redbud Trees in Bottomland, Near Red River Gorge, Kentucky, a puny version of which can be seen via the Metropolitan Museum of Art (far better to see this as a print or reproduction in a book, though).
As alluded to above, Cercis canadensis is commonly called redbud, or a bit more specifically, eastern redbud. The cultivar ‘Forest Pansy’ is a popular choice among many gardeners, partly due to its purple foliage (along with many other fine qualities; see the Plant of Merit designation of Cercis canadensis ‘Forest Pansy’ from the Kemper Center for Home Gardening).
You have perhaps noted that the flowers of eastern redbud emerge directly from the branches and stems, a phenomenon called cauliflory (as opposed to emerging from buds on new growth or young stems). Wayne Armstrong has an extensive article on cauliflory, along with an explanation of its adaptive advantages. It is worth noting, as Mabberley does in The Plant-Book, that cauliflory is a trait almost exclusively found in tropical trees, with Cercis being one of the few exceptions. This property, combined with the disjunct distribution of Cercis in western North America, eastern North America, Mediterranean Europe and eastern Asia, suggests that Cercis was once more widespread during the periods when present-day northern temperate areas had tropical and subtropical climates.