264 MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 
A large shrub or more commonly a small tree; introduced from Europe and 
more or less naturalized in the regions indicated ; commonly produces more 
viable seeds than S. americana; 104,700 seeds per pound. 
OJ)servations: Three species of birds, including sharp-tailed grouse; song- 
birds generally ; claimed to be a second choice of birds where this and 
S. americana grow together. 
Sorbus californica, see Sorhus sitchensis. 
Sorbus decora, see Sot'tus amet^icana. 
Sorbus dumosa, see SorMs scopiilina. 
Sorbus occidentalis (Wat«.) Greene. Alpine mountain-ash. 
S. pumila Raf., Pry us occidentalis Wats., 
Range: 4, 12. 
Site: Well-drained, sun. 
Fruit : Pome, available August-December. 
A large shrub ; flowers June-August. 
Ohservations: Oregon jay; Clark's crow. Important locally as browse for 
livestock, although susceptibility to rust lessens the brawse value. 
Sorbus pumila, see Sordus occidentalis. 
Sorbus scopulina Greene. Greene mountain-ash. 
8. clumosa- Greene. 
Range : 4, 9, 10, 12, 18, 14. 
Site: Well-drained, moist, sun, shade. 
Fruit : Pome, available July-December. 
A large shrub to small tree ; flowers in June ; commonly occurs in sandy or 
gravelly soil. 
Stomach records: Dusky grouse. Where in association with highly palatable 
species is little cropped by livestock; elsewhere excellent browse for sheep. 
Sorbus sitchensis Roem. (pi. 40, A). Pacific mountain-ash. 
)S. angustifoUa Rydb. (?), 5^. californica Greene, Pyrus sitchensis (Roem.) 
Piper. 
Range: 4, 12. 
Site: Dry, well-drained, moist. 
Fruit : Pome, available August-November. 
A large shrub to small tree ; flowers in June ; thicket forming ; occurs in 
sandy loam and other soils. 
Stomach records: Three species of birds, including Richardson's grouse. 
Fair browse for sheep, less so for cattle. 
Sphaeralcea davidsonii, see Malvastrum davidsonii. 
Sphaeralcea fasciculata, see Malvastrum fascictilatum. 
Spiraea spp. Spiraeas. 
Nearly all species are free from insects and diseases; most occur in neutral 
soil. 
Stomach records (in addition to specific records) : Ruffed grouse, sharp- 
tailed grouse; mountain sheep. Observations (in addition to specific records) : 
Pica, cottontail rabbit. Palatability of the western species to livestock is low. 
Spiraea albla Du Roi. Meadow spiraea. 
Range: 15 (Black Hills), 21, 22, 25, 26, 27, 28. 
Site : Well-drained, moist, sun. 
Fruit: Follicle. 
A small shrub : flowers June-August. 
A possible hybrid between this and S. tomentosa has been described as 
;S^. sutcanescens Rydb. It occurs in region 28. 
Spiraea arbuscula, see Spiraea densiflora. 
Spiraea caespitosa Nutt. Dwarf spiraea. 
Petrophytum caespitosum (Nutt.) Rydb., P. acuminatum Rydb. 
Range: 4, 9, 10, 11, 13, 15. 
Site: Dry, sun. 
Fruit: Follicle. 
A small, mat-forming shrub; flowers in May; occurs on limestone and other 
soils; will grow over dry bare rocks. 
