POPULUS, Salicaceae. Poplar. Fast-growing trees often used 
for screen plantings. None is suitable for small gardens. They 
are objectionable as city street trees because their vigorous 
roots often clog sewage pipes [3C, nursery]. 
P. alba. White P.; Eu. to W. Siberia and C. Asia. 
P. a. Richardii. 
P. canadensis (P. deltoides x nigra) aurea. 
P. c. Eugenei. 
P. c. marilandica. 
P. c. regenerata. 
P. deltoides. Cottonwood; Que. to N. D., Fla. and Tex. 
P. Maximowiczii. N.E. Asia, Japan. 
P. nigra betulifolia. Black P.; Eu. 
P. n. italica. Lombardy P. 
P. “Rumford” (P. nigra x laurifolia). 
P. Simonii fastigiata. N. China. 
P. szechuanica. W. China. 
P. tomentosa. Chinese White P.; N. China. 
POTENTILLA, Rosaceae. Cinquefoil. The varieties of P. fruti- 
cosa are low shrubs that produce yellow or white flowers and 
bloom for many weeks. P. tridentata is a prostrate spreading 
species with white flowers suitable for the rock garden [5E, 
nursery]. 
P. fruticosa. N. hemisphere (My.-Au.). 
P. /. mandshurica. Manch. 
P. /. montana. 
P. f. parvifolia. C. Asia. 
P. /. Veitchii. C. and W. China. 
P. tridentata. Lab. to Tenn. to Man. 
PRINSEPIA, Rosaceae. Spiny shrubs that produce their leaves 
very early in spring. The flowers are not conspicuous as they 
are largely hidden by the foliage [nursery]. 
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