Found my notes:
Table 2. Mean Levels of Ephedrine and Pseudoephedrine
(Percentage of Ephedrine-E, and Pseudoephedrine-PE)
Species - Geographic Area - E - PE
Ephedra major - Spain, Sicily, Afghanistan, Pakistan - 1.9% - trace
Ephedra sinica - Northern China to Outer Mongolia - 0.76% - 0.28%
Ephedra equesitina - Inner Mongolia - 1.25% -0.58%
Ephedra intermedia - Pakistan to Mongolia - 1.15% - 0.084%
Ephedra gerardiana - Northwest Himalayas, northern India, western Pakistan, Tibet, and Szechwan and Yunnan provinces of China - 0.77% - 0.10%
I took this from a document called "Ephedra: A Potential Precursor for D-Methamphetamine Production" - May 1997 written by NDIC - (I think).
The original link to this is in the meth forum. Because I've made so few posts you should be able to find it there if you seach my posts in that forum.
I found that Ephedra sinica grows very slowly in temperate climates (London, UK) but that Ephedra equesitina does well.