For that you would have to check with your state regarding whether a license is required and getting a tax id number.
There is a lot of things to consider from how you are going to set up the business as a sole proprietor or a LLC. Getting the licenses and you may have to make sure your zoning allows your type of business. You also have to keep records for taxes. If you want to expand and need a loan, you may have to have a business plan. It doesn't sound like it should be so complicated but you know government likes complicated. At a bare minimum, you need the licenses, and be able to keep good records. Zoning and any regulations that would be required. Locally you might not have a problem, but you will have to make sure the plants are healthy and pest free.
http://www.madeinalabama.com/assets/201 ... nswers.pdf
Happy gardening in Hawaii. Gardens are where people grow.