GERMINATION AND SEEDLING ESTABLISHMENT OF SPINY HOPSAGE IN RESPONSE TO PLANTING DATE AND SEED-BED ENVIRONMENT

Reestablishment of spiny hopsage (Grayia spinosa [Hook.] Moq.) in the shrub steppe requires development of appropriate seeding technology. W e examined the effect of planting date and seedbed environment on germ ination and seedling establishment of 2 seed sources at 2 southwestern Idaho sites. Seedbeds were prepared by rototilling. In 1987-88, seeds collected in 1986 were drilled at 66 viable seeds m-1 of row at Birds of Prey in late fall, winter, and early spring and at Reynolds Creek in late fall, early spring, and late spring. Seeds collected in 1986 a nd 1988 were broadcast at 400 viable seeds m-2 at both sites in late f all, early spring, and late spring 1988-89. Seeds in nylon bags were a lso planted at each site in late fall, winter, and early spring in 198 7-88 and in late fall, winter, early spring, and late spring in 1988-8 9. On each succeeding planting date and in early summer, 5 bags of eac h seed source from each of the earlier planting dates were recovered. Water content, viability, and germination were compared among seeds fr om previous plantings and control seeds stored in the laboratory. Each year, first-year seedling establishment at both sites was favored by late fall compared to other planting dates. In 1988, seedlings establi shed only from late fall plantings at a density of 1 m-2 at each site. In 1989, late fall planting at the 2 sites increased seedling establi shment 6 (51 vs 8 M-2) and 20 (41 vs 2 m-2) times compared to early sp ring planting. Germination was generally greater for seeds incubated a t field sites compared to controls. Germination total and rate increas ed 6-11 times and 13 days from late fall 1987 to early spring 1988, 1- 6 times and 4 and 9 days from winter 1988 to early spring 1988,17 time s and 10-11 days from late fall 1988 to winter 1989, and 4-7 times and 11 days from winter 1989 to early spring 1989. Late fall or early win ter planting is essential to permit early spring germination when surf ace soils are moist.