Container tomatoes for winter...

Got my greenhouses this spring and want to try some winter tomatoes. :-)
I bought three lovely little vines in 6' pots from Lowe's, one 4th of July, one Better Boy, and one Patio.
They are about 12" tall and one has some sets on it already. I have put them into some good soil from the hen yard in 3 gallon pots in the greenhouse that gets the most sun.
Is a 3 gallon pot large enough for a single tomato vine? I have placed cages in the pots for them to be tied to as they grow.
Thanks!!! K.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.