ASPEN IN THE CENTRAL ROCKY MOUNTAIN REGION 5 
THE TREE 
Aspen is a tree of extremely variable development in the Rocky 
Mountain region, ranging from little more than a shrub on sites at 
high altitudes and northern latitudes to trees that may attain a 
diameter of 38 inches at breast height, and a height of 90 feet in 
exceptional cases. (PL II.) In general, the trees in the intermoun- 
tain region range from 8 to 14 inches diameter at breast height at 
maturity, with heights between 50 and 60 feet. 
The age of aspen varies greatly with site. Single trees as old as 
200 years, and whole stands as old as 150 years still existing in 
even-aged form, have been found on first-class sites. On other sites, 
in the thicket type, the trees may become decadent as young as 40 
years. Good aspen will usually live to an age of 120 years with 
little external appearance of deterioration. Most of the large trees 
seen in the mountains of Utah are over 100 years old, but seldom 
over 130 years. Very old trees are usually too much decayed to 
allow complete ring counts, and, in fact, trees over 14 inches in diam- 
eter, breast height, are usually more or less decayed. (See also 
" Diseases and injury.") 
LEAVES 
As described by Sargent (13) aspen leaves are ovate or semior- 
bicular, abruptly narrowed at the apex into short, broad points, 
regularly serrate, with small, incurved, callous, glandular teeth, 
except at the broad slightly cordate truncate, or rarely wedge- 
shaped, base; thin and firm, dark green and lustrous above, pale, 
dull, yellow-green below, iy 2 to 2 inches long, and broad, with 
slender veins forked and united near the margins and reticulate 
veinlets; their petioles slender, compressed laterally, iy 2 to 3 inches 
long. 
FLOWERS AND SEED 
At high altitudes, aspen flowers before the snow is off the ground 
in May or even in June. In central Utah, at least, only a small per- 
centage of the trees bear flowers, large areas remaining without 
them year after year. The staminate and pistillate catkins are borne 
on separate trees; the staminate trees are much more frequently 
found than the pistillate, which are very rare indeed. As a result, 
practically no seed is produced, and as the seed develops in June 
during a period of low precipitation and high evaporation, it often 
dries before it is mature. The viability of the seed is low, and as 
the seed bed is dry and unfavorable at the time of dispersal, repro- 
duction by seed is unknown in this region. It may, of course, take 
place to a very limited degree at rare favorable intervals (#). 
According to Sargent, the flowers are formed in aments \y 2 to 2y 2 
inches long, the pistillate being 4 inches long at maturity, their scales 
deeply divided into 3 to 5 linear acute lobes fringed with long soft 
gray hairs; disk oblique, the staminate entire, the pistillate slightly 
crenate; stamens 6 to 12; ovary conical, with a short, thick stype and 
erect stigmas thickened and club-shaped below and divided into lin- 
ear diverging lobes. Fruit matures in May or June, oblong conical, 
light green, thin walled, nearly one-fourth inch long, seeds obovate, 
light brown, about one thirty-second inch long. 
