I have seen this subject debated other places, but I'm not sure there is a definitive answer. Many people feel that foliar feeding in orchids has limited value because orchid leaves have relatively few stomata, so the fertilizer doesn't enter the plant easily. Others swear by it. I have seen foliar feeding formulations, and my biggest question has been whether or not foliar feeding products could be used for root feeding. I haven't gotten a straight answer about that either.