This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
These have been included under herbaceous plants, but they are worthy of special mention, for they are among the best of our hardy border plants. These fine varieties are obtained from several species: P. suffruticosa, P. maculata and P. paniculata. They are not of great value as cut flowers, but you will never make a mistake in recommending them wherever a hardy border flower is wanted. New varieties are of course raised from seed.
The young shoots root freely in May, or as soon as you can get them after the plants start to grow, and can be grown in pots and planted out in September. They also divide with the greatest ease, either before they start to grow in spring, or in October and November. No plant is hardier. There are so many fine varieties that there is no excuse for growing poor ones.