If I had to venture a guess - you don't seem to understand your marketplace. I don't mean you don't understand online sales - I mean you don't understand small growers (specialty nurseries).

I grew up around small growers (Near Lancaster, PA). Most of the growers I know don't really use the web for sales (or much of anything) - you might think that's good since that's what you are offering but that means in order to sell to them you first need to educate them on the web and then try to make the sale.

Grower's don't live and breath the internet like we do...by trying to sell them through email you have cut your chances of a sale to almost nil - you might want to try snail mail, a phone call or better yet a sales call in person in this case.