Are these cuttings you have planted or standard sized nursery plants? If the latter, you do not need to use any root stimulator.......roots grow naturally all on their own and quite well at that :-) Root stimulators - apart from rooting hormones used in propagation - are unnecessary and sometimes harmful amendments. SuperThrive, starter fertilizers, B1 root stimulators, etc., do nothing significant to aid in plant growth but are all produced to get you to spend money needlessly.

The best thing you can do to stimulate root development and guard against possible transplant shock is to prepare the planting area carefully and to water the plants in properly after planting.