Rosemary has many well known health benefits but scientists are now studying its specific effects with regard to memory with outstanding results.
Rosemary is a wonderful herb with a tradition of use spanning millennia. It has innumerable uses in both the kitchen and in herbal medicine.
Did you know that rosemary has been associated with memory enhancement since ancient times? It is true – and it has even been referred to from the latter part of the Elizabethan Era to the Early Romantic period as the herb of remembrance. In Shakespeare’s Hamlet, Ophelia says, “There’s rosemary, that’s for remembrance.” (Hamlet, iv. 5.) It has also long been used as a symbol for remembrance during weddings, war commemorations and funerals in Europe and Australia.  Mourners in old times would wear it as a buttonhole, burn it as incense or throw it into graves as a symbol of remembrance for the dead.
It seems that this tradition of Rosemary may actually far more ancient and have its origins in the Arabic world of medieval times, which was greatly advanced in science: In Henry Lyte’s 1578 “Niewe Herball“, an English version of Rembert Dodoens’ French treatise, it is written “The Arrabians and their successors Physitions, do say that Rosemarie comforteth the brayne, the memory and the inward senses, and that it restoreth speech, especially the conserve made of the flowers, thereof with Sugar, to be received daily.” 
Because of this seemingly esoteric association, rosemary has at times been made into a sort of herbal-amulet, where it was placed beneath pillowcases, or simply smelt as a bouquet, and it was believed that using rosemary in these ways could protect the sleeper from nightmares, as well as increase their memory.
What’s fascinating is that several scientific studies have now found remarkable results for rosemary’s effects on memory:
Rosemary essential oil’s role in aromatherapy as an agent that promotes mental clarity was validated by the study of Moss, Cook, Wesnes, and Duckett (2003) in which the inhalation of rosemary essential oil significantly enhanced the performance for overall quality of memory and secondary memory factors of study participants.
More recently, in 2012 a study on 28 older people (average 75 years old) found statistically significant dose-dependent improvements in cognitive performance with doses of dried rosemary leaf powder. 
Another study by Mark Moss and Lorraine Oliver at Northumbria University, Newcastle has identified 1,8-cineole (a compound in rosemary) as an agent potentially responsible for cognitive and mood performance.
Further studies by Mark Moss and team have found memory enhancements of up to an amazing 75% from diffusion of rosemary essential oil. 
Now if you are asking “How is it even possible that an aroma can enhance memory?” – well, that’s a great question. Here’s a fascinating quote from one of the scientific papers referenced: “Volatile compounds (e.g. terpenes) may enter the blood stream by way of the nasal or lung mucosa. Terpenes are small organic molecules which can easily cross the blood-brain barrier and therefore may have direct effects in the brain by acting on receptor sites or enzyme systems.” 
Terpenes are primary components of essential oils and are often strong smelling, responsible for a diverse array of natural aromas. It’s also been found that 1,8-cineole enters the bloodstream of mammals after inhalation or ingestion. 
I’m interested to know if anyone uses rosemary as a memory enhancer. Maybe you could take some with you next time you have an examination and see if it helps with recall? One last tidbit to inspire you further: Lavender. In a 1998 study published in the International Journal of Neuroscience, rosemary was found to increase alertness but lavender was found not only to increase alertness but also to increase accuracy in math tests!  The way this is going, I can sense the possibility of a magical custom oil blend for total recall!
Rosemary is very easy to grow in many gardens and will provide an abundant supply – almost too abundant! Just the other day when paying a Christmas visit to my family, I cut a few sprigs from my Dad’s organic rosemary bush (rosemary is an evergreen!), left them on a radiator to dry for a few days and then put the needle-like leaves in a jar, ready for use in the kitchen whenever required. So aromatic… and much better than the store-bought stuff I had before!
Another thought that springs to mind from this – here we have yet another example of an ancient herbal lore that has been validated by modern experiments. This happens again and again – and yet still the remarkable herbals, lost treasures of the ancient world are considered spurious by modern medicine. If an herb has been in use for a thousand years for a condition, it should be considered probable that there is something to it. When are we going to catch up with ancient knowledge? Let’s hope soon – while there is still some untarnished, un-GMO-ed nature left…
This scientific discovery was brought to our attention by the remarkable Robert Tisserand, whose work on essential oils is considered by many to be among the very finest. Check out his original pages reporting on the memory effects of Rosemary here http://roberttisserand.com/2013/04/new-rosemary-memory-research/ – and here http://roberttisserand.com/2012/03/rosemary-boosts-brain-power/
References: Henry Lyte “Niewe Herball”, 1578, p.264 http://books.google.com/books?id=ifxNAAAAcAAJ&pg=PA264  http://www.awm.gov.au/commemoration/customs/rosemary.asp  Moss M., Cook J., Wesnes K., & Duckett P. (2003). Aromas of rosemary and lavender essential oils differentially affect cognition and mood in healthy adults. International Journal of Neuroscience, 113(1): 15-38. Retrieved 24 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/12690999  http://www.ncbi.nlm.nih.gov/pubmed/21877951
Credits: Herbs-Info. Guest contribution.