Lilacs

When we bought this house last summer, there was a big blossoming white lilac tree in the back. At the start of this spring we hacked it all back to keep it under control and to stop it shading over our new grass. And now, the young shoots at the back are blossoming. Not white, but purple. Is this possible? Normal? Is it a second lilac tree that never got to show off because the white one was so gregarious? The photo above is not of our tree, still google imaging.