Ask-a-Dave's-Gardener: Variety of tree dahlia?, 1 by torbiecat

torbiecat wrote:
I\'ve had \'dahlia imperialis\' (double whites and single lavenders) in my garden for a few decades. From seemingly out of nowhere, the garden is sprouting healthy, prolific dark purple singles with bright yellow boss--and I\'ve been at a loss as to what kind of dahlia they are and how they just appeared miraculously. I did just watch a YouTube video that showed ones that look just like my new ones, calling the variety \'excelsa\' and remarking how \"promiscuous\" they (all dahlias?) are--Is that what I have in my garden? Is the \'excelsa\' a variety of the \'imperialis\'? See pic--
Thanks-- Torbie in San Francisco