A month ago I found two tomato volunteers, decided to pot them and keep them indoors till next spring.
They are in quart--sized pots and have grown to about 8 inches. They are in my native soil mixed with a little potting soil. I've reactivated my grow light, for their sake, as my south facing windows still don't provide enough light. I set my indoor temperature to about 69 ° F. during the day and 61° overnight.
I'm wondering if I ought to give them a little fertilizer from time to time. I don't intend to re-pot between now and spring. The little things look good and healthy now but it will be at least 5 months until they can be set out into the garden.
I overwinter tomatoes in the house in front of a south facing window. I use pots that hold about 2 gallons. I don't fertilize them. Room temperature is whatever the ambient temperature is, which is around 65F. I don't give them any extra light. I'm interested in making a few manual cross pollinations during the winter, and getting seeds from them, so that I get two generations per year on my breeding projects. I only need a few fruits with a few seeds to move the project forward, so I am only interested in survival of the plants, not optimal growing conditions.