Doris Hoover spent years studying Hesperoyucca in southern California. She found offset-forming and once-flowering plants mixed together in different proportions in different parts of the region. There was also variation in whether the pups formed next to the mother plant or at a distance. Difference in leaf shape (length vs. width) was more constant within each area, with longer leaves and earlier maturity near the coast. Plants with flowers marked with dark purple (pollinated by black yucca moths!) were only found southward from Santa Ana Canyon and San Gorgonio Pass.