What can I do to plant a tomatoe when my soil is mostly clay ?

You can grow tomatoes in containers just make sure they are big enough for the variety you are planting.

Clay soil requires amending before anything can be planted. Get a good gardening book, or go online, and research double digging. It allows you you to mix in amendments while loosening the clay base, and creating a good planting surface but it is time consuming! Good luck!

That depends on how much time and energy you want to put into it. For a quick fix, go buy a bag of potting soil, cut a 4" X 4" square out of the middle (after you have laid it down flat). Poke a few holes in the bag underneath for water to run out so that the roots of your plant don't become waterlogged. Plant your tomato plant, right in the square spot of the potting soil bag. You won't have to worry about weeds or anything. Just keep it watered!

For the Long Term, you are going to want to mix potting soil, vermiculite, and sand in with your clay. This can be rototillered in or just worked in with your shovel (back-breaking work). Do small areas (4' X 4' ) at a time. You've got to condition the soil or your tomatoes will never grow. They are acidic and your clay soil is basic. You've got to make air pockets for the roots to wiggle around in and thrive. That's what mixing all that good stuff into the soil will do. And, to be on the safe side, take a sample to the county extension office and ask them what additives you need to add to your soil to help it grow better tomatoes after you have conditioned it. It may be all ready perfect, or more things may need to be added. They can be a very big help.

Plant the tomato in a large planter. Be sure to use organic potting soil. You can add some Basil and Marigolds (both good companions for Tomato )to create a Mini Garden.

If you really want to plant in ground you'll have to incorporate some well rotted compost into your clay soil.

Tomatoes are susceptible to verticillium wilt so be sure to rotate where you plant them or change the soil in the planter every season. Good Luck!

If you don't mind spending the money, look into an Earth Box. There are home made versions of the boxes if you do a search.

Get a cheap tub from a dollar store, punch a few holes in the bottom and fill with good potting soil.