I sow the tomato seeds in those tall thin Elmlea pots, of which I am so fond, and keep them in a warm place (the airing-cupboard usually) until germination (about 4 days later).
After spending about two weeks in the Growlight House, the young seedlings get their first taste of Outdoors when I take them outside for a couple of hours on a still sunny day (if there is one!).
At this stage, light is even more important than heat. Without it the plants will go long and thin. Mine are borderline this year - certainly skinnier than I would like, but then I don't control the weather...
For the next three weeks or so the plants spend as much time as possible outside, weather permitting, and are brought in at night. By this time they will be starting to outgrow the Elmlea pots, and the nutrients in their compost will be fading, so it is time to do the first transplanting.
Ideally, the plants should go into pots that are deep enough to allow them to be submerged right up to the level of their first leaves, but unfortunately if I were to use pots of that type they would be too big to conveniently allow me to bring them indoors when necessary. For this reason I usually put them into pots that are 15cm in diameter, like this:
These are "conventional" pots, and are about as tall as they are wide. Most pots you see on sale in Garden Centres and supermarkets are of this type. The Elmlea pots are 11.5cm tall, so when my tomato plants come out of the Elmlea pots, their roots already go down about 10cm+, so in the new pots they are at approximately the same level in relation to the soil surface - although of course they have a lot more room to spread out. This is not ideal. Deeper would be better, because tomato plants will develop additional roots from any part of the stem that is under the soil, and more roots make for a stronger plant.
What I really want is pots like this, especially the green one.
These two pots are much taller than usual, in relation to their diameter. The green one is 23cm tall and 15cm wide. The black one is 20cm tall and 18cm wide. In other words, both pots would allow me to plant a tomato much deeper than usual. I have looked for pots like this, with a view to buying some, but I haven't seen any on sale. I have a suspicion that the green one once held an orchid plant purchased from Tesco or somewhere similar! I think I must search on the internet and get some before this time next year (it's too late for this year).
So, for the time being, my tomatoes have to go into a miscellaneous collection of pots of various sizes:
Fat ones, thin ones, black ones, green ones, terracotta-colour ones - whatever is available!
In another two or three weeks the tomatoes will go into their final homes, and a second transplanting operation must take place. The exact timing of this depends a lot on the weather, because once they go into their enormous containers (with their 1.5m canes) I will definitely not be able to bring them indoors any more.
This next photo is from 11th May 2014. I think this year's plants are not going to be that big in just ten days from now.