NATURAL REGENERATION OF DOUGLAS FIR. 59 
FORM. 
The crowns of open-grown trees with good growing space are pyramidal 
and become broadly rounded or flat-topped in old age. In forest stands the 
boles are usually clear of branches for more than one-half the height of the 
trees. The clearing of side branches begins at an early age in complete 
stands, but in open-grown trees these branches are persistent and become 
large. The usual diameter of mature trees is 3 to 4 feet, and the height is 
175 to 250 feet. Trees even larger than this are common. The largest 
authentic diameter recorded is 18 feet at 6 feet above ground, and the 
greatest height is 325 feet. 
BARK, 
On trees 10 to 15 years old the bark is about one-fourth inch thick, smooth, 
lustrous, and grayish to brown. It becomes ridged on trees about 30 years of 
age, and on old trees it grows to be 8 to 14 inches thick, dividing into large, 
rounded, irregular connected ridges. Some old trees have bark 18 to 24 inches 
thick at the base. The bark scales off and forms mounds around the bases 
of the trees. These mounds make good insulation against fire. 
ween. 
The wood is light red or yellow, with heavy white Ls ol The seedlings 
become lignified when 30 to 40 days old and at that age begin to be resistant 
to “ damping-off ” disease. 
: LONGEVITY. ) piace 
Stands 300 to 450 years old are common, and some stands older still have 
been noted in the region studied. The best development of the tree is during 
the first 200 years. The oldest tree noted was 739 years of age. 
