The ecological life history of tall bluebell, Mertensia arizonica Green var. leonardi (Rydb.) Johnston (M. leonardi Rydb.), was investigated during 1963 and 1964. Summer field studies were conducted on the Mud Creek Sleep Allotment of the Uinta National Forest, Wasatch County, Utah. Laboratory and herbarium studies were carried out at Brigham Young University. Specific objectives were to investigate seed germination, seedling development, root system, phenology, palatability, and describe the physical site factors where bluebell occurred. A study of this species was necessary because much of the herbage produced in certain areas of aspen range is not utilized. This condition occurs when mature stems become infected with powdery mildew during mid-July, collapse onto the ground, and dry up. This plant also becomes the dominant forb under certain grazing conditions, and appears to crowd out other desireable forage species. This tall bluebell species occurs throughout the length of central to northern Utah and into southwestern Wyoming and southeastern Idaho, constituting up to 37.1 percent of the understory ground cover. The seed have impermeable seed coats with scarification resulting in a germination percentage of 0.0 to 26.0. Emergence percentages of 21.0 to 53.0 were obtained from field plantings. The period of greatest seedling mortality coincided with the development of permanent wilting conditions at the 6 and 12 inch soil depths during both summers of field study. Studies of transplanted seedlings show that 1 to 2 years of developmental growth are required prior to developing the first single flowering shoot. Mature root systems consist of a semi-fleshy "caudex" from which several main roots extend to a depth of 3 to 4 feet and terminate in fine roots extending beyond to a depth of about 7 feet. Numerous fine roots are concentrated in the upper 1 to 3 feet of soil. Variations in soil texture, structure, pH, total soluble salts, and percent organic matter were not found to alter the basic pattern of root development and distribution. Once plants are established, active growth of stems commences at time of snow melt, and continues 6 to 7 weeks when an average height of 19.5 to 31.0 inches has been reached. Stems elongate as much as 1.4 inches per day with a peak occurring midway in the growing period. Flowering begins about 4 weeks after snow melt and lasts 2 to 4 weeks. Mature seed are shed 18 to 28 days after flowers open. Temperature appears to constitute a significant factor of initial growth and flowering rates. Lodging of bluebell stems occurs with wilting or fast falling rain. The first severe wilting occurs between July 21 and August 13. This coincides with the occurrence of permanent wilting conditions at the 6 and 12 inch soil depths. Wilting is followed by maturation and drying of stems. The latter event is often associated with mildew infection caused by Erysiphe cichoracearum. The occurrence and rate of increasing infection appears favored by high temperature and low humidity. Sheep utilize bluebell up to 44 percent by mid-July. Cattle utilize bluebell up to 46 percent, while deer were not found to utilize bluebell at all. The pocket gopher, Thomomys talpoides was also observed to utilize bluebell stems and inflict injury to main roots.



College and Department

Plant and Wildlife Sciences



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Bluebells, Utah; Botany, Utah; Natural resources, Utah