Answer: What a nice surprise! Your volunteer tomato may or may not resemble the original tomato because of cross-pollination in the field where it was first grown, but whatever fruit your plant produces will be edible, just the same.
Tomatoes grow best in full sunshine and will drink as much water as you provide. In fact, it will grow and set more fruit if it receives water on a regular basis. Water thoroughly when the top inch of soil dries out. Depending upon the size of container, this could be daily, every other day, twice a week or once a week.
Tomatoes are either indeterminate or determinate in their growth habit. An indeterminate tomato plant will continue to grow and flower (and produce fruits) all summer long; a determinate plant will grow to a specific height, then flower and produce fruit all at once.
Obviously, an indeterminate tomato type will need lots of room to grow. A determinate type will be bushy rather than leggy.
A cherry tomato won't need much room to grow at all.
So, armed with the above information you should be able to decide whether or not your volunteer tomato plant needs to be transplanted into a larger container or if it will be happy in its current home.
Best wishes with your volunteer tomato!
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