I did Environmental Management through SIT and it was a really good quality course. The course was free, except for the course materials (about $60 a paper for my one).
I did notice there were two Hort courses - one of them organic. Would love to do these at some stage as I live on a lifestyle block.
So as for SIT themselves, I had a good experience there. You can ask the tutor questions online, and also share information/questions with other course members.