One of the plants with a long herstory of magical use is Mugwort, Artemisia vulgaris. A name sprung forth from Artemis herself.
Mugwort promotes dreaming, both while we see and letting them come to life. Mugwort has also been traditionally used to keep evil spirits at bay, cleanse negative energy, and has been slipped into shoes to act against weariness in travel.
Lavender is added to soothe and create spaciousness. California poppy rounds the edges of sharp, unconscious material we meet in dreams, allowing the dreamer a little ease.