In all of my years of gardening, have never seen a tree like this.
The one I saw, was about 30 ft. tall, no leaves this time of year, but had (the best way I can explain it) knees, all the way up the trunk & limbs & every knee, had a cluster of tiny purple flowers.
Am going back out this coming weekend, & will get pictures, but am very curious as to what this is????
Knees might be where branches were pruned off way back when, might not have anything to do with the flowers per se. Redbuds can have blossoms pop right out of the bark, so some trees can do this. While we wait for you picture, you might look at pictures of Redbuds (Cersis sp)
Redbud is the tree that comes closest to have blossoms on the bark, but here are some other trees that get purple floweres before they get leaves:
Jacaranda, Wisteria, Magnolia x"Jane", Paulownia tomentosa,