Once frost is out of the question and night temperatures don’t fall much below 10C (50F), it’s safe to put the young tomato plants into their permanent spots. In my case, that’s the biggest plastic pots I can get my hands on–the kind nurseries use for young trees and larger shrubs. This year I have nine pots.
A week or two before transplant day, I prepare a soil mix that consists of the contents of last year’s tomato pots and a generous helping of fresh compost plus bagged manure. I also add lime, because tomatoes prefer a soil with a pH close to neutral, and mine is somewhat acid. Too acid a soil leads to a calcium deficiency which produces blossom end rot.
My plants are of the indeterminate type, which means they keep growing indefinitely, unlike the determinate or bush types. The plants were already starting to grow tiny new shoots in the leaf axils when I planted them. I remove those. Left alone, they would turn into additional stems. It makes no sense to let potted tomatoes grow extra stems, but three stems per plant may be manageable in plants grown in the ground.
In any case, the plants will need to be supported as they grow, which means cages or stakes. Cages are preferable for my pot-grown tomatoes, since the pots sit on the asphalt driveway. Plants in the ground may be staked–3 or 4 stout stakes per plant with twine wrapped around them. In my experience, mature plants that have set fruit always get unwieldy and need extra supports for their last month or so.
But that’s in the future for these plants. For the next few weeks, all I have to do is supply water, remove those unwanted leaf axil shoots, and wait for the plants to produce flowers.