In several respects the flora of the Tetons is unique. The high mountains have constituted a barrier to plant migration which many forms could not cross; hence the range limit of a number of plants is found here. Representatives from north, south, east, and west are found in this general region, this being the limit, in many instances, of their distribution. There are many plants typical of the central Rockies, and a few known only to this range. Five life zones are recognized within the park, all occurring in a distance of less than 15 miles. Plants migrating from other regions have grown equally well in each zone.

The flowering period begins in the park as soon as the ridges and flats are free of snow in May, and it continues until about August 15 in the Arctic-Alpine Zone. Hence, plants of at least one zone and usually of several may be seen blooming at any time in the spring or summer.

The evergreen trees form an appropriate frame for the majestic Teton peaks and are reflected in the beautiful lakes which they encircle.

Lodgepole pine is the most common tree, covering the floor of the valley and extending up the mountains to about 8,000 feet. The pines may be easily distinguished from the other evergreens by the long slender needles occurring in bundles. Lodgepole has two needles in each bundle. Trees of this species were extensively used by the Indians for lodge poles.

Whitebark pine is the tree of timber line; the occasional specimens found at a lower elevation are usually dwarfed. Needles occur five in each bundle; cones 2 to 3 inches long and almost ovate; the tree is much-branched and of medium size.

Douglas tree has been called "Douglas spruce", "Douglas fir", and "red fir"; however, it is neither a spruce nor a fir but is worthy of separate distinction. One needle; cones 2 to 4 inches long; a three-lobed bract projects from beneath each scale of the cone, a very distinctive character; common at middle elevations.

Alpine fir grows from the base of the mountains to timber line; at high altitudes it is dwarfed and sprawling. One needle, flat; cones 2 to 3 inches long, scales paper-like; tree usually pyramidal and beautifully symmetrical.

Engelmann spruce is the largest tree in the park, and is usually found growing in moist places and near the lakes and streams. One needle, square in cross section, stiff and sharp; cones 2 to 3 inches long, scales papery.

Blue spruce is not common and is found only in the Snake River bottoms. The form found here is not typical, lacking the blue cast. One needle, square in cross section, stiff and sharp; cones 3 to 5 inches long, scales papery.

Creeping juniper is not common. It is a prostrate form, lacking definite trunk. Leaves awllike, one-half inch long or less, stiff and sharp, spreading from the twigs; fruit, berrylike.

Aspen is the most common deciduous tree of the valley, growing on the slopes up to about 8,000 feet. The leaves are on very slender stalks and the slightest breeze puts them into motion, hence the popular names "Quaking asp" and "Quaking aspen." Leaves rounded, 1 to 3 inches broad, with a slender stalk of about the same length; bark smooth and whitish.

Balsam poplar is found along some of the stream banks and is the largest deciduous tree of the park. Leaves about 3 inches long and 2 inches broad, longer than the stalk; bark smooth on the young trees, becoming rough as the trees get older. The small seed pods contain many seeds, to each of which is attached a tuft of white hair or "cotton"; hence one of the common names, "Cottonwood."