Dirt, same here for me. It is only the old fashioned bleeding hearts (dicentra spectabilis) that goes dormant in the summer. I have 'Luxuriant' and fringed bleeding hearts (dicentra eximia) and they keep their foliage all season and do bloom on and off after the first spring flush. I didn't know that little tidbit about 'Luxuriant' being a hybrid of those three species - learn something new every day
