Tanacetum huronense - while this is an endangered species in its native habitat, it appears to me that it could become invasive in fertile soil. Three small seedlings from 1998 have become a solid 2 ft. by 2 ft. block of attractive ferny plants in 1999. Height = 20 inches
Tanacetum vulgare - this is my ladybug factory. From May through July, this 4 ft. by 8 ft. stand is loaded with thousands of adults, larvae, and pupae. The larvae often fall off the plants, and the stems of surrounding lawn grass are loaded with pupae up to 2 ft. away from the tansy. These plants can grow to 7 ft. high, so I normally keep them trimmed to about the 5 ft. level. The tansy aphid must be present for full factory output, and there are some years when they don't arrive here.
Tanacetum niveum - this is far and away the most attractive tansy that I have seen. I like it even more than my wonderful painted daisy (T. coccineum). Unfortunately, it is biennial in my garden, and the seeds are of medium difficulty for starting. It grows to about 30 inches in height and makes a very nice cut flower.