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 fairly good trade is done in these plants, which are invaluable for rockeries and borders, to which they give a glow of beautiful purple in spring. They may be increased from seeds, division, or cuttings - the two latter methods being the only way to keep choice varieties pure. The work should be done in early autumn. Any ordinary garden soil will suit so long as it is well drained. The best-known species is A. deltoidea, with lilac-purple flowers; but perhaps the best for selling is "Dr. Mules", a fine form of purpurea with vivid purple-violet flowers. Another good form is "Lloyd Edwards", with large deep-purple flowers. Other kinds are Campbelli, grandiflora, Leichtlini, Moerheimi, Prichard's Al, W. Ingram, Hendersoni, Eyrei, Froebeli, and violacea.