Heritage Perennials - Profile with description and horticultural details. (zone 2-9) (1 photo)
Iris' Garden - Gardener in the Netherlands presents a photo of this plant, with basic horticultural information. (1 photo)
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) (4 photos). Also a page for 'Thriller'.