City Farmers in City Heights. They are a great local nursery and have pretty much anything you could want. It's a fun place to visit. :) I also like Walter Andersen on the coast, a bit north of downtown. I don't know of any places directly in the South Bay, but City Farmers would only be a 10-15 min drive.

Welcome to SD!

Here is a link that might be useful: City Farmers

Thanks for the info lwpmeg!

If you don't mind the drive up to Walter Andersen in Point Loma (Sport Arena Area), then you should also check out Mission Hills Nursery. It's a small local nursery with a lot of interesting finds.