From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-1889-681148
Question: I have a tiny backyard, but would still like to plant some
herbs and flowers. I'm planning on using individual pots or
windowboxes. How large should the containers be for herbs like basil,
cilantro, and chives? for tomatoes? Can I plant cherry tomatoes in a
hanging basket?
Answer: In regions with hot summers, the larger the container, the
better. A cherry tomato will grow in a hanging basket, and a standard
tomato can be grown in a five gallon bucket or half a whiskey barrel
planter. An oversized windowbox can hold several basil plants along
with a clump of chives and some cilantro. These plants (and perhaps a
parsley plant or two) would also do well in a half barrel along with a
tomato plant because they all like a rich soil that is evenly moist
yet not soggy. Standard window boxes as a rule are not deep enough or
wide enough to provide enough room for the roots of tomatoes, but
could hold the herbs if you are willing to water very often (perhaps
twice a day) in the heat of summer.