Soil for tomatoes
Last year was the first year I grew tomatoes. Overall, it went pretty well, and the plants were reasonably prolific. I haven't started anything for this year, and if I decide to, I know I have to do it soon. Here's my question: I have the pots from last year, with the soil still in them. Do I have to change the soil if I buy new seedling plants, or can I just use the pots with last year's soil? My perennials (mostly herbs, but also a small Alpine strawberry plant, which is already almost fully grown in terms of leaves and some blossoms) are doing fine in their old soil, but I don't know if tomatoes are different.
You're growing in pots only, right? Definitely grow your tomatoes in new potting soil. If you use a potting soil with a time-release fertilizer make sure you don't fertilize the pots until the time released stuff has worn out. The bag should specify how long it will last.
Your perennials and alpine strawberries should be, at the very least, fertilized regularly this year if they are to remain in the same soil. If they are crowding the pots or are root bound, either repot them into larger pots or divide them into more pots. If the alpine strawberries have more than one crown, they can be divided too.
Plus its very possible there are limited nutrients left in that soil from the previous year's growing, as they were used up by the plants.
I would dump out the left over soil (or start a small compost pile with it), wipe out the pot down with some water and peroxide, to kill off any possible fungus or diseases that may have built up. Fill the pot up with some newer nutrient rich soil or compost, and start your planting.