Rooting powder comes in different concentrations. Hormex makes a #1, #3, #8, and #16, with #16 being the highest concentration around 1.6%. Some online propagators of hard-to-root plants like Protea say that Hormex #16 is the only concentration that they have seen work. This got me to thinking. Is there ever a reason with any plant to not use the highest concentration hormone you can find? They cost about the same amount, so why not just always use the highest concentration?