DBA (doing business as) is a fancy way for companies to call themselves another name for legal reasons (kind of how Fanta soda is actually a sub business of Coca cola...)
After some googling, it seems as though Helen's nursery is called Hamblin's now? If so, the company Seedable Plants LLC has completely different owners listed for their company, and there is nothing relating the two companies together. There isn't much information about what Seedable Plants LLC actually is. Is it a Nursery?
I would love to get my hands on a book like that.
