Hi Tomatoes like onions and they grow quickly so I would spot them between the tomatoes. They are suppose to improve the taste of the tomatoes. I'm doing it this year so I'l let you know here in a few weeks. My first tomatoes have just shown up on the plants and I'm so excited.
Tomatoes are heavy feeders so they like 50% compost in their soil when they are planted. It sure worked for mine. I did that this year and although they were slow to start growing
now they look fantastic. It's the first year I've had really good looking plants and loads of buds. I also sprinkled fireplace ash lightly around their dripline underneath the grass clippings.
The grass clippings are to help keep the soil moist because it dries out quickly here in Virginia.
like a lot of water. But becareful not to get the leaves wet.
Watch out for Bottom End Rot and if you see it add calcium to the soil.
That's about all I can think of. And I've learned it all right here at the a garden forum.