I don't know of an online program, maybe someone else might. Have you contaced your state university, it's county extension program or your local master gardener program? If not, perhaps the link below will help you find a contact.

The programs may vary, understandably, from one state to another, but I thoroughly enjoyed my classes through Rutgers University here in New Jersey. It was more than just the course material, but the interaction and bonding with my classmates, that made this such a wonderful experience. I wholeheartedly recommend it for anyone who has the interest, as well as time and energy - remember, being a Master Gardener requires a commitment to give back a prescribed number of hours of serving the community through horticultural helplines, projects, etc.

Good luck to you!

Diane

Sorry, forgot to add the link.

Here is a link that might be useful: AHS links to MG websites in US & Canada

I know that Oregon State offers an Online MAster gardeners course, but I don't know about out-of-staters. ( you must be judging by your zone)