Is this the one you mean Paul ?
http://www.henriettesherbal.com/pictures/p14/pages/trifolium-medium.htm
I don't know if you know this site ? but it's very good for references
http://culturesheet.org/doku.php?id=fabaceae:trifolium:medium
I know it used to be sown to make clover hay with other varieties (they thrive in slightly different conditions) and was known as cow grass.
I'm lazy about clover, and I'm wary of ones that don't look well. I pick the red the white and the arrow (zigzag?) as I find them looking pert and ready. The arrow one doesn't dry as well as the red one though. I really only use them as teas. I know that there's a cultivated white clover that is not good to use though....glycerides or somesuch, I need to go and look it up, but I know that plant geneticists have bred some varieties now that don't have the problem......I'm still a bit wary of white clover that's growing where fields might have been planted.
Not much help I'm afraid, I just use both the reds (one is sometimes called purple, and it's the red, red iimmc) kind of indiscriminately.
cheers,
Mary
p.s. A book worth begging, stealing or borrowing (and no you can't have mine unless you're here to read it
)
Herbal Drugs and Phytopharmaceuticals: A Handbook for Practice on a Scientific Basis ,Bisset, N.G. & Wichtl, M., (Eds), Medpharm Scientific Publishers, Stuttgart, 2nd Edtn., 2001
M