Gardening and Horticulture - hanging pots

I am growing a tomato plant upside down from a basket and i wonder if there are any companion plants or herbs i can plant in the topside that will help fertilize the tomato's or help the growth of the tomato.

Generally speaking plants do not fertilize each other. Some plants, such as clover, will fix nitrogen in the soil and that would be a fertilizer. You can plant other plants that will help to repel bad insects and/or attract beneficial insects. It's often called companion planting. Here's some combos. This first one is great for crossreferencing both the veggie crop and the recommended combos. Loads of great info.
http://www.ghorganics.com/page2.html
http://www.moonsweb.com/companions.shtml
http://www.livingherbs.co.nz/companion.htm

Parsley and basil are two good companions. The parsley is larval food for the swallowtail butterfly, so don't be surprised if you see their caterpillars. I plant extra parsley for them. Chives are supposed to improve the flavor of tomatoes. Chives, or any member of the onion family, will help to repel aphids.

Newt

thanks newt, I wonder what the taste difference is with chives being planted near tomato's are like.

You are very welcome! That's a good question. I've not heard anyone mention any taste problems.

Newt

with chives being kinda like a onion i wonder if it would give it a hint of that flavor?
not sure i want that.