Development of Creosote Bushes and Clones Recently, however, another line of evidence suggested that individual creosote bushes were already growing at low elevations in the Mojave Desert long before the decrease in pinyon and juniper in that region, and perhaps even before the time that creosote bushes colonized the Chihuahu.an Desert (as indicated by fossils of pack rat nests). This new tine of evidence indicates that clones of creosote bush may have been continuously in residence in the southwest Mojave Desert for nearly 12,000 years. The latter line of evidence is based on the development and growth rate of individual creosote bushes and clones. Upon germination of a creosote bush seed, the first stem grows to a height of only a few cm when a branch is formed. The main stem area from which the first branch originates is the stem "crown" from which future branches also originate. Later branches originate around the periphery of the stem crown. As the stem crown grows in diameter, the center of the plant is occupied by old branches and new branches continue to be produced around the periphery of the stem crown. The branches grow upward a meter or so, the whole. shrub having an obconic or somewhat rounded shape. As growth continues, the oldest branches gradually die and the stem crown splits or segments into functionally separate crowns. This happens at an age of 30 to 90 years, depending on the location. On sites with better soil moisture conditions, growth is more rapid and segmentation occurs earlier. After segmentation of the stern crown, the original stein and the early branches die and eventually rot away. The connections between adjoining segments of the Excavated plant at the time of early segmentation; about 89 yars old. Note the relatively short, stout stem crown below the branches; note the smaller diameter of outer (younger) branches; also note sandy gravelly soil. Excavated young "seedling," with the upper parts of branches removed, about 9 years old. Note the several branches at about the same level and the solid, cylindrical stern crown below the. branch crotch; this stem crown would be solid and nearly circular in cross section. Top view of segmenting plant with tops of stems removed. Note dead center and dead central branches, and live branches around the periphery; plant about 49 years old but developmentally more segmented than the plant in the above photo.

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