10 Joshua Tree Seeds to Grow as Bonsai Tree. Yucca brevifolia, the Joshua tree is a typical species of the Mojave desert in Califonia, Arizona, Nevada and northwards to Utah. The species name brevifolia comes from the Latin for short leafed. The tallest trees reach about 15 meters tall. Yucca brevifolia is great for a bird garden and a butterfly garden. The trunk of a Joshua tree is made of thousands of small fibers. Older plants form a sturdy trunk that supports many crowns with typical spikey leaves. Yucca brevifolia’s foliage color is green, evergreen. The rigid leaves are linear, bayonet-shaped No stratification needed, soak the seeds for 24 hours in water and plant 1/8 inch deep in Fox Farms Ocean Forest Soil or CZ Grain soil or another all natural soil. Not Akadama or other soil for mature bonsai.