HARDY PERENNIAL PLANTS 193 



will need this treatment about once in two years, as they are in- 

 clined to get weak when they remain long in one place. 



Propagation. Seeds should be sown during March, in the 

 greenhouse. The seedlings are quite small at first, and^they should 

 be allowed to m.ake considerable headway before being potted off. 

 They are also propagated by division, October being the best 

 month for dividing. 



IBERIS (Candytuft). The perennial species are in reality 

 dwarf, evergreen shrubs. They are attractive in appearance all 

 the year round. They come in bloom the latter part of April and 

 last till the end of May. There are about half a dozen species and 

 varieties. /. sempervirens and /. 5. superba are the best; they grow 

 from 9 to 1 2 inches high. /. semperflorens is a taller growing species 

 with large, pure white flowers. /. Tenoreana grows about 6 inches 

 high. It blooms in May; flowers purplish white. /. corifolia has 

 the flowers in flat, compact heads. I. gibraltarica is the largest of 

 all; the flowers are white, tinged with pink. It is the most striking 

 and showy of the perennial kinds. It is somewhat straggling in 

 growth. /. g. hybrida is more compact, with the flowers at first 

 white, changing to rosy purple. They succeed best when let alone. 

 Once planted and not disturbed, they soon form a dense 

 foliage. 



Propagation. Although most of the species produce seed 

 freely enough the seedlings are of a straggling growth for the first 

 season. Much better plants are raised from good-sized cuttings 

 taken at the end of September, and put in sand, in a cold propagat- 

 ing frame. If kept close and moist they will root well. The cuttings, 

 when rooted, should be put in 3-inch pots, and plunged in a cold- 

 frame for the Winter. 



IRIS. There are fully 170 species; the varieties of some of 

 them are numerous. The genus is divided into two sections. In 

 one section, known as Xiphions, the species have bulbous, tuberous 

 root-stocks; one or two of them, such as /. reticulata and /. persica, 

 produce the flowers before the leaves. (Discussed on page 264.) 

 In the second section many of the species have thick rhizomes, 

 which creep along the surface of the soil, or a short distance be- 

 neath. To this section most of the very numerous garden varieties 

 belong. They are known as German Irises, but having been in 

 cultivation for a long time, it is impossible to tell just from what 

 species some of them have originated. 



