This comes as gospel fact from my grandmother and others that Yucca leaves when ground into a slurry and used as a growth promoter can be as effective as growth hormones found in kelp, alfalfa, willow new growth and even the commercial growth promoters. Grandma used to grind them by hand. I use a flea market blender purchased for a couple bucks. I effectively have used whatever Northern variety is t common to North Central Pennsylvania, zone 4. Here they seed themselves from where the seed falls or the birds move the seed about. I never planted a single one of the several that grow and bloom here.