Liquid root stimulators are used to help plants grow strong roots. Unlike powdered rooting hormones, root stimulating liquids are meant to support existing roots, rather than encouraging new roots to form. They're intended to be used when planting bare-root nursery plants or when transplanting perennials, trees or shrubs. Opinions differ as to whether liquid root stimulators have any beneficial effect as far as helping plants thrive.
Choose a liquid root stimulator that contains nitrogen as well as other nutrients. Some root stimulators contain only vitamin B1, and according to Arizona Cooperative Extension, there's no proof that vitamin B1 alone will have any beneficial effect on your plants.
Mix the root stimulator and water in a bucket or plastic bottle according to the manufacturer’s instructions. Different brands require different dilutions.
Water your plants with the diluted root stimulator the same way you would water them with plain water. Unless your specific plant requires soaking, do not over-water.