DESCRIPTIVE AND SELECTIVE. 251 



POLYGONUM. — ^The flower-lover who sees a snowy 

 mantle of the lovely Polygonum Baldschuancium spray- 

 ing itself over an arch or round a pillar is little likely 

 to associate the genus with the rockery. There are, 

 however, some Alpine species. Afflne, sometimes called 

 Brunonis, is quite dwarf, and a very pretty plant, with 

 rosy flowers in late summer or autumn. It will thrive 

 in gritty loam, and may be propagated by seeds or 

 division in spring. 



POTENTILLA (Cinquefoil).— Most of the Cinque- 

 foils are too strong for small rockeries. They are 

 handsome plants, with foliage resembling that of the 

 strawberry. The rock gardener whose space is very 

 hmited should leave the florists' hybrids alone, in 

 spite of the great beauty of their flowers. He 

 should content himself with one or two of the Alpines, 

 such as ambigua, with yellow flowers in summer ; and 

 nitida, of which there are several varieties, with white, 

 pink or rose flowers. They are not at all particular 

 as to soil, thriving in gritty loam. Propagation is by 

 seeds or division in spring. 



PRIMULA.—See Chapter XI. 



PULMON ARIA. —See Mertensia. 



PUSCHKINIA. — ^This is a small genus, and only 

 one variety is grown, namely, scilloides ("Scilla-like''), 

 sometimes called lihanotica. It is a low-growing bulb, 

 bearing white, blue-striped flowers in spring. This 

 charming little plant is well worth a sunny nook in the 

 rock garden. It will thrive in almost any gritty soil, 

 and may be increased by division every third or fourth 

 year. 



