In common with other regions of high altitude, the flowering time for plants in the Park is relatively short. The seasons vary greatly, depending largely upon the snowfall. While nearer normal, the present is at least a month later than last year.

The earliest flowers to appear are normally in the lower levels. Many of these have a comparatively longer flowering season and a greater altitudinal as well as geographical distribution, following up to higher levels with the advance of the season. Of these, Phlox Douglasii (Douglas's Phlox) is a noteworthy example. In the Lava Beds Monument it was out during the month of May; a month later it was in flower in the yellow pine zone of the Park, and late in July it was in all its glory on the lower slopes of the Watchman and the pumice fields to the north and westward. Even as late as the middle of August this ubiquitous plant will follow the last of the lingering snow-drifts farther up the slope.

Of the earliest and more fleeting flowers to appear in the hemlock zone, might be mentioned the yellow Erythronium (E. grandiflorum pallidum) which adds much to the floral beauty of Sun Creek Valley, and the Western Windflower (Anemone occidentalis), so attractively decorating the first bare spots at the entrance of Castle Creek Garden. In their restricted habitats, they come immediately after the disappearance of the snow, and follow closely the retreating drifts, their season being regulated by the depth.

A number of the more conspicuous plants are not in flower until the season is considerably advanced, or even well into the second half. These, for the most part, continue to flower until early snowfall. As common elsewhere, members of the Aster family dominate. Of these, one of the most widely distributed and attractive perennials is Engelmann's Aster, sometimes know as Colville's Aster. The many tall leafy stems form large rounded or spreading clumps. By the latter part of August the purple flower-heads will add much to the color of the pumice flats and slopes, notably about Government Camp and the Rim area. Intermingled with it, or dominating some areas, will be bright golden-yellow spots and patches of Bloomer's Rabbit Brush (Chrysothamnus bloomeri). In less abundance is the gray-leaved Rabbit Brush (C. nauseosus speciosus). On the slopes of Garfield Peak it can be seen along the trail. Just at this time one of the most attractive of the late bloomers is the Western Boneset (Eupatorium occidentale). This, with its many-stemmed pink or lavender-colored flower-heads, is rather abundant and especially noticeable on the lava flows of Wizard Island, and more common along the rocky lake shore at the Wine Glass. Everywhere on the pumice fields of the upper areas, is the Pyrola-leaved Eriogonum (E. pyrolifolium). By the first of August, the tall corn-like stalks of the green False Hellebore (Veratrum viride) with their panicles of greenish-white flowers will be much in evidence, and the pink-flowered common Fireweed (Epilobium angustifolium) will be at its best. The Silver Plant (Raillardella argentea) forms shining silvery mats on the higher summits. More rare and seldom seen by visitors to the Park, are the bog-loving Parnassia intermedia with its white buttercup looking flowers, and the beautiful little gentian (Gentiana simplex). with its single deep blue flower. These two plants are to be found at Boundary Spring and Copeland Creek. It is interesting to note that the common sagebrush (Artemisia tridentata) which contributes so much to the gray color of the plaints and deserts of the west, occurs on the dry talus slope of the crater wall at the Wine Glass. There it is associated with the yellow pine and other plants of the Transition life zone. It will not be in flower before the last of August, which is about the time it will be out in the Lava Beds area.