FIFTY BEST ROCK PLANTS 323 



grown. It varies a good deal in size, and pains should 

 be taken to get the dwarfest variety. 



There are not many rock plants that flower in au- 

 tumn, and one of the best of these, where there is 

 space for it, is Polygonum vaccinifolium, a perfectly 

 prostrate Knotweed with pink blossoms in September 

 and October. It spreads rapidly, and its shoots root 

 in the ground as they spread. It should be grown in 

 poor soil and in an open position on the north side 

 if it is to flower well. It can be readily increased by 

 rooted shoots cut off and replanted in spring, but 

 should not be disturbed when established. Other 

 plants that will flower late in the year are Papaver 

 alpinus and Linaria alpina. These often die after 

 flowering, but if raised from seed in spring in a cold 

 frame and planted out as soon as possible they will 

 come into flower about July and continue to bloom 

 till the frosts. They can also be sown where they 

 are to bloom. They will flourish in any well-drained 

 position not too dry and seed themselves profusely. 

 Both are extremely beautiful. 



Few of the Pentstemons are true perennials, but 

 P. glaber alpinus lasts as long as any, and is a true 

 rock plant. It varies in colour, but the best varieties 

 are a beautiful glass blue. It can be easily raised 

 from seed or increased by cuttings. Of the Colum- 

 bines, Aquilegia Pyrenaica is the dwarfest and a very 

 beautiful plant. It is easy to grow in a cool well- 

 drained place, but difficult to get. A. alpina is never 

 seen in its true beauty in England. It seems to de- 



