Native Vegetation 
45 
tatoes, alfalfa, Canada field peas, and some of the hardiest fruits 
and vegetables. The tenderer fruits and melons are not a success, 
as might be judged from the mean summer temperature, the short 
frostless season (average, 103 days) and the average date of the 
last spring frost (June 11). 
TABLE XVII.—TEMPERATURE, SAN LUIS VALLEY. 
Station 
Altitude 
Mean Annual 
Temperature 
Mean Winter 
Temperature 
Mean Spring 
Temperature 
Mean Summer 
Temperature 
Mean Fall 
Temperature 
Aver. Length 
Frostless Season 
Aver. Date Last 
Spring Frost 
Aver. Date 
First Fall Frost 
Absolute 
Annual Range 
Blanca . 
7865 
42.6 
23.4 
.... 
.... 
• • • • 
103 
June 11 
Sept. 21 
108 
Garnett . 
7576 
40.5 
18.8. 
41.3 
60.6 
41.2 
95 
June 6 
Sept. 12 
115 
Manassa . 
7700 
42.4 
22.7 
41.7 
60.6 
43.4 
90 
June 4 
Sept. 9 
101 
Saguache . 
7740 
43.5 
22.0 
43.5 
62.3 
45.2 
124 
May 26 
Sept. 25 
112 
San Luis . 
7794 
42.6 
22.7 
42.2 
60.2 
44.8 
106 
July 5 
Sept. 20 
111 
Average. 
42.3 
23.9 
42.2 
60.9 
43.7 
103 
June 11 
Sept. 18 
109 
CHAPARRAL OR BRUSHLAND 
Chaparral is a dense growth of shrubs. It is synonymous with 
thicket. Chaparral in Colorado is mainly o<f scrub oak ( Quercus 
spp.), or buckbrush ( Symphoricarpos spp.), or mountain mahog- 
ony ( Cercocarpus pamrifolius) , or Juneberry {Amelanchier) , or 
“canyon thicket” composed of chokecherry ( Prunus melanocarpa ), 
thornapples {Crataegus spp.) , and others. 
Scrub oak forms the most extensive thicket growth in the 
State. It is absent from the northeastern part of the State, from 
North Park, Middle Park, and South Park. Its northernmost limit 
along the eastern front range is somewhere between Palmer Lake 
and Denver. It is sometimes an alternating association with pin- 
yon pine-juniper; again it may form a distinct fringe along the 
upper edge of the sagebrush association. As a well-defined chapar¬ 
ral, oakbrush is seldom above 8,000 feet. Although it is growing 
under a wide range of climatic conditions, such as is found be¬ 
tween 4,000 and 9,000 feet, its upper altitudinal limit, as a well- 
formed plant community, is not above the limit of the successful 
growth of alfalfa, potatoes, small grains, strawberries, hardy cane 
fruits, and the hardy vegetables. 
In western Colorado, oakbrush is commonly associated with 
buckbrush {Symphoricarpos spp.). Both scrub oak and buckbrush 
usually occupy a soil that is deep, rich, and suitable for agricul¬ 
tural purposes. The hill slopes in Fig. 15 show patches of scrub 
oak and buckbrush. 
