Buy the 2015 Old Farmer's Almanac!
Reporting
Hi, Ailie: It somewhatHi, Ailie: It somewhat depends on the type(s) of tomato, but it sounds to us like your answer is four. Put one plant in the center of each of the four quadrants of your box.

2015 Garden Calendar2015 Weather Watcher's Calendar2015 Recipes Calendar2015 Engagement Calendar 2015 Everyday Calendar2015 Country CalendarNew Year Cross StitchLobster Rope Doormats