I could just DROOL over your greenhouse. If you are interested in going into business, Treva, there are several things you can do. Contact your state Dept. of Agriculture to see if there is any information they can provide you with about becoming a small scale nursery. You will also probably need to go through your county office to file an application for a business permit. In Texas they call it a DBA license. It costs $7 here, and it gives you the legal right to name your business whatever you call it when you apply for the license and it authorizes you to do business there. Check with your state comptroller to find out what you need to do to get a tax license. Here in Texas and elsewhere, if you sell things to people in your own state, you are required to charge sales tax on what you sell. Then you arrange with the state to pay the taxes either on a quarterly, semi annual or annual basis. With the sales and use tax permit (which is what it's called in Texas,) I can send copies of that to companies with whom I do business when I order supplies for my business and they do not have to charge me tax. If you buy supplies for your business that will be used in a product you sell for retail, you don't have to pay tax. You will have to pay tax when you sell it to people locally. You may have to look into what various states require when you ship things from state to state. California has some of the most restrictive laws in the country.
If you want to sell things online, the easiest way to start out is E-Bay, but you have to pay fees to list your products and fees to PayPal for handling the transactions. Until you establish yourself and get a significant amount of business, I wouldn't bother with any type of merchant account. The expense of that is far too great for it to be of benefit to you.
Look into places where you might be able to sell stuff locally -- farmer's markets and that sort of thing are often ideal places for selling plants. If you have a nursery license, you may also be able to sell to smaller scale plant stores or garden centers.
Where there is a will, there's a way. It will be tough and it will take a while. I've been trying to make a go of it with my candles for 3 years.....Business happens a drop at a time. Don't give up, though! If anyone can do anything, YOU CAN! You survived Katrina and look what you've accomplished since then!