By Park Naturalist, Edwin D. McKee*

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*Material obtained on a reconnaissance trip for the purpose of making general observations, studies and collections of the biological and geological features of the region made during the period of April 8 to 14, 1934.

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The flora of the Grand Canyon National Monument represents several distinct plant associations, each of which is different and in contrast to that, with Saltbush predominating, along the approach road across the great alkaline plains to the northeast. The main groups of plants in the Monument are controlled principally by factors of soil and climate and for the most part are rather distinct in their constituents although gradational along their borders. They are listed by the writer as (1) the high mountain type, (2) the valley wall type, (3) the open valley type, (4) the inner canyon rim type, and (5) the lava bed type. In the first two of these, representing the high altitudes, plants are almost if not entirely the same as those found in corresponding life zones in Grand Canyon National Park to the east. In the lower two, many of the plants are of species unknown in eastern Grand Canyon, while the open valley type is intermediate in its status.

HIGH MOUNTAIN TYPE, REPRESENTED ON MT. TRUMBULL AND NEIGHBORING VOLCANIC PEAKS, ALTITUDE 6,250 - 7,500 FEET:

This type corresponds to the upper part of the upper Sonoran and to the Transition Zones as found on the Kaibab and Coconino Plateaus to the east and essentially all of its plant species are found in those areas. A few typically Canadian Zone species are found in sheltered places on the mountains.

List of conspicuous plants in lower part.
(c) - very common:

List of conspicuous plants above spring, near top of Mt. Trumbull.
(c) - very common:

VALLEY WALL TYPE, REPRESENTED ON BOTH SIDES OF TOROWEAP VALLEY, BROKEN WALLS OF SEDIMENTARY ROCKS, ALTITUDE 5,000 - 6,250 FEET:

This type corresponds closely to the upper Sonoran Zone as found on the Coconino and Kaibab Plateaus to the east, with essentially all of its species also found in those areas.

A few typically Lower Sonoran species are also found in this association on the more open slopes. Both because of a lack of time and because the flora was so similar to that of the National Park area, a rather incomplete list was made of this type.

Partial list of conspicuous plants:

OPEN VALLEY TYPE, REPRESENTED IN TOROWEAP VALLEY - A WIDE FLAT PLAIN FILLED WITH ALLUVIUM, ALTITUDE 4,250 - 6,000 FEET:

Since this valley includes most of the area to be developed as an antelope range, its flora is of considerable interest. At the present time it is very badly overgrazed and includes a surprisingly small number of species. Indeed there are only four or five different plants that can really be considered common in this area.

Partial list of conspicuous plants.
(c) - very common:

INNER CANYON RIM TYPE, REPRESENTED AT JUNCTION OF TOROWEAP VALLEY AND GRAND CANYON EXCEPT ON LAVA FLOWS. RED SANDSTONE AND SHALE OF THE SUPAI FORMATION. ALTITUDE 3,250 - 5,000 FEET:

This type is characterized by a peculiar mixture of fairly well developed Upper Sonoran species together with a great number of those typical of the Lower Sonoran Zone. Many of the latter are of species not represented farther east in Grand Canyon, even at lower altitudes, and others have attained a remarkably large growth.

The apparent excessively favorable conditions for the development of Lower Sonoran types in this area seem incongruous when it is considered that fairly large Pinyons, Junipers and Sagebrush occur mixed with these. From this it would seem evident that the temperature is not the principal controlling factor in this area. Probably a more favorable supply of moisture explains this phenomenon, however, no concrete evidence was obtained to substantiate this suggestion.

Specific example of plants illustrating the unusual conditions represented in this area are the Ocotillo and Creosote Bush, plants that have not been recorded from farther east in Grand Canyon, and the shrub Thamnosmia which in one place has actually developed into the proportions of a tree, 15 feet high and with a basal trunk diameter of 14 inches, looking strangely similar to a huge broom pointing skyward. The exceptionally great size of the Broad-leaf Yuccas and the rigidity of their leaves are also noteworthy local developments.

Partial list of conspicuous plants.
(c) - very common:

(Some others which appeared to be different from any found in eastern Grand Canyon but which have not yet been identified, were collected.)

LOWER LAVA BED TYPE, REPRESENTED BY BASALT FLOWS FROM VULCAN'S THRONE AT LOWER END OF VALLEY INTO INNER CANYON, ALTITUDE 3,250 - 5,000 FEET:

This area, although representing about the same altitude as the preceding, is characterized by a very distinct plant association. Like the preceding, however, it contains many species not found in eastern Grand Canyon and many Lower Sonoran types which have attained exceptional size. Most noteworthy in the latter group are the Barrel Cactuses which grow to a height of four feet and the Chollas which appear in clumps, 25 to 30 feet in diameter and as high as a man. Since among the plants not known to the writer were several of the most common species, the following list loses most of its value until determinations make it possible to supplement the names of these.

Partial list of conspicuous plants.

(c) - very common.