I agree about asking to take cuttings from a shrub with the flower colour that you want.
Thay are easy plants to grow, but inclined to windrock damage, being quite shallow rooted, so I do a bit of a tidy up in the autumn, then the proper cut back early in spring. That way I dont end up with a monster that needs support!
Just to confuse the issue, I also grow the annual mallow seeds as well. J.