Cultivars vs Species for Medicinal Use

Do cultivars have the same medicinal value as the species plants? For example, would E. purpurea 'Flame Thrower' be medicinally equal to E. purpurea? We are incorporating medicinal herbal plants in our gardens and wildflower meadows, but I am uncertain as to whether I should include the showier cultivars - or if I do, whether or not I can use them for herbal medicine.

The easy answer, some times yes, and sometimes no. This has been the center of many debates as herbalists try to use local species as much as possible vs the traditional species found in the old literature.
I believe the final conclusion that most herbalists agree with is that one needs to compare the tastes of the different species for an organoleptic comparison of constituents, as well as compare when possible the chemical analysis of the species with a database such as Duke's ethnobotany database. That can be found at: www.ars-grin.gov/duke/
For example, yarrow now comes in a variety of colours, and so long as the taste is similar to white traditional species, it is now regarded as being similar in medicinal action.
So, you need to develop your sense of taste and get out and do a compare and contrast with your different species. However, caution is indeed warranted, as some plants have very close cousins; one may be poisonous where another is a food.

For another response on the issue of species vs cultivars, please

check out the

question, Yarrow "Paprika" as Effective as Common Yarrow? below in the Medicinal Herbs Q & A.