This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
A distinct-looking Chinese perennial, 3-6 ft. high, with somewhat triangular coarsely toothed leaves, and large bright rose-red Foxglove-like flowers drooping from an erect spike, and speckled or blotched with purple, and tinted with yellow in the throat.
R. chinensis (or glutinosa), 1-2 ft., is another species not so well known, with dull-purple flowers striped with deeper tints. Both kinds are best treated as half-hardy annuals or biennials, and are raised from seeds sown in heat in spring. Another species is Henryi, 12-18 in. high, with yellow and white flowers spotted with red. Hybrids have been raised between chinensis and Henryi, and also between the latter and angulata.