Missouri Botanical Garden - Plantfinder page for one of the plants growing at the garden, with usually one or more photos, horticultural information, and noteworthy characteristics. (zone 3-8) (7 photos). Also a page for 'Altifolius'.
NARGS - Plant of the month portrait, with description and information about cultivation and propagation. (1 photo)
NARGS Image Gallery - Photograph(s) contributed by North American Rock Garden Society members. (4 photos)
Plant Delights Nursery - Catalog page with photo, horticultural basics, and descriptive blurb. (additional pages for other varieties) (1 photo). Also a page for 'Cliffwood'.
Rob's Plants - Plant profile with basic horticultural information and often personal observations. (6 photos)
(1 photo).