True unicorn root may be used as a visionary summoning device for those who work with unicorns. (Another very powerful botanical goes by the name false unicorn root.) True unicorn root is extremely endangered becoming as rare as unicorn sightings. Grow your own if you'd like to work with it.
Surround yourself with images of unicorns if it helps; otherwise affix your goals and desires in your mind. Hold onto a piece of unicorn root during psychic journeys. This piece of root may be used indefinitely, however, reserve it for this magickal purpose. Wrap it in white satin in between uses.
Unicorns are also said to congregate where apple and ash trees meet. Create a unicorn friendly grove of apple and ash trees and keep your eye out for appearances. It is also believed that Unicorns live among ash trees, and if you carry a bit of the wood or leaves, you may see one. Or lie down in a grove of ash trees, place an ash leaf on your chest, and wait for one to make itself known.
From: The Element Encyclopedia of 5000 Spells