Your mention of the leaves is one reason why I wanted a true species double. The ones I have do not match the doubles mentioned in most sales literature. Mine are much shorter, about 12-14 inches rather than the 20 inches usually mentioned. Klehm's sent a catalog to me which had a P.tenuifolia ssp. lithophile which I should have ordered as part of my FL collection. $28.95 was not a bad price for a FL.
Update: I called Klehm's and they have the P.tenuifolia ssp. lithophile in stock and are still shipping. They had a 3 cultivars for two sale but I only needed the FL. My lucky day.
