I bought the big bag-o-potting mix from the store for my seeds. I haven’t tried growing broccoli, but I hear its a rather big plant and I have a small garden, so I don’t think I will try. I saved all of our tp cardboard rolls over the winter for starting seeds, as well as several cardboard egg cartons. The egg cartons were easier to plant in since they were connected, but I think the larger cardboard tubes (I cut them in half so they are about 2-3 inches tall) will be great for the tomato plants I am starting. Good luck with the garden!