Mugwort (artemisia vulgaris). Mugwort is known as one of the magical herbs (of the saxons?) and is mentioned almost every where to induce vivid dreams and more. I tried it as a tea with some dried mugwort several times. It did not seem to have any particular effects. I tried it with fresh leaves that i am growing at home - nothing. I tried it as a "dream pillow", where you put some herbs in a little pillow case - nothing!
I have also tried rosemary as it is supposed to increase memory and help remember dreams. It seems to work slightly better than the mugwort. I tried it as a tea and also by putting some rosemary plants in pots next to my bed.
I have tried other plants that helps to relax and induce sleep, and they seem to work: valerian roots, chamomille, catnips, etc...
Concerning the dreams and the memory, I even tried pills of melatonin and it does not seem to have any noticeable effect on me.
I have had the feeling that what works best is actually not the plants we are using but our disponibility of the mind. When I think and I concentrate to have vivid dreams and I autosuggestion myself, it seems that it works best, without any respect to which herb I use. The same for relaxing. I can cut the coffee and drink all kind of relaxing herbs, but if someone upsets me for some particular reason I will get upset no matter what. On the other side if I don't drink any herb, but drink coffee, but I do have a nice day, then I'll be clam and relax.
So, I am not sure how all these works. Probably these plants are "helper", but basically it is up to our mind to go all the way to where we want to go, whether it is about having vivid dreams or about relaxing.
What does work for you?