This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Tuberous or thick fibrous - rooted plants with grass-like radical equitant leaves. Flower-scape usually flattened and two-edged. Flowers umbellate or solitary. Perianth regular, spreading or campanulate, segments equal, tube short. Stamens on the throat of the perianth. Stigmas three, entire, chiefly from North and South America. The etymology of the name is uncertain. There are two or three hardy species in cultivation.
1. S. Bermudianum, syn. S. anceps. A dwarf species from 12 to 18 inches high, with linear leaves and a sharply two-edged flower-scape. Flowers few in each umbel, bright blue, perianth-segments mucronate. A native of North America, flowering in Summer.
2. S. convolutum, syn. Marica convoluta. - A rather tender species about six inches high, growing in dense tufts. Scapes about 3- or 4-flowered. Flowers yellow, appearing in May. South America.
3. S. grandiflorum. - A pretty tuberous-rooted plant with the aspect of Iris Xiphium. Scapes nearly round, bearing 3 or 4 large campanulate purplish-violet or white flowers. This is the handsomest of the genus and one of the hardiest. It is a native of North America, and blooms from April to June.
There are several other less hardy species occasionally seen : as, S. bicolor, violet spotted with yellow; S. odoratissimum, with very fragrant white flowers; and S. Ccdifornicum, with bright yellow flowers.