Really pretty Wildcat, I've not seen the 'Petite Sirah' before.
My Wildcat 'Bobcat' is spiking just now, I usually get two spikes per year but always together from the same growth as it only usually puts on one growth a year.
They CAN spike from older growths which most people don't think they can. Mine had trouble in the first couple of years with something eating all the new growths, I was about to give up on it because it only had old growths when it suddenly spiked again from a growth that had already had two spikes. So I gave it a reprieve thinking I would chuck it after the flowers... but by that time it had started a new growth and this time it didn't get eaten