Growing tomatoes is great fun but time consuming as the plants need a lot of attention especially as the growing season goes on, which is why they are colour coded red Tomatoes are vigorous plants and even more so this season and are already mature enought to pot on into a larger container or grow bag for the rest of the season. If you haven't grown Tomatoes before how to tell when they are ready to pot on? The photos on the left are both ready; the single Tomato plant looks self evidently too big for the pot, and top heavy. The other Tomato plants look bushy and mature and they too are ready.
I plant into a trough filled with the contents of a grow bag or good quality compost rather than direct into the grow bag. There are two advantages, firstly you can get better support for the plants with the greater depth of soil provided by a large container. It is hard to imagine now, looking at these plants, but they will be very tall, 1.5 m plus and heavy with fruit needing a lot of support. Secondly, for watering, often with a grow bag the water can run off the grow bag rather than drain into the plants. If you are using grow bags a good tip is to use wide tape to tape up the bag to make it more round and less flat where tomatoes are growing.
Plants will need attention on an increasing basis from now until the end of the season, nipping out the side shoots and regular watering and feeding. For more tips on growing tomatoes follow the link.