| A 20 inch pot will grow almost anything you can grow in the yard (including some trees). Go NO LESS than 15" (5 gallons or 20 quarts) for any kind of tomato or bell pepper unless it's Cherry or Paste tomatoes (which typically require only 4 to 5 quarts of soil). The best place I've found to get them so far is at Cottage Farms Direct. Since containers do tend to dry out more than the ground does, I would highly reccomend a plastic tin of Hydrogel (such as Terra-Sorb) to mix into the container soil. As for the type of tomatoes, that would depend on what she likes. My personal opinion would be for heirloom varieties, but if she's not into seed saving you can go with a nice hybred. With a 20 inch container, you have room for companion planting too. For tomatoes, I would reccomend a mix-and-match of: For improved flavor of the ripe tomato:
Basil (also repels flies and mosquitoes)
Parsley
Oregeno
Chives (Also repels Aphids and Japaneese Beetles) For Pest Control:
Dill - attracts White Flies away from your plants
Nasturtium - repels aphids, cabbage worms, colorado beetles, wooly aphids, squash bugs and white flies
Lemon Balm (AKA Bee Balm)- Attracts Bees and other pollinators Good Companions (though not sure why)
Carrots
Green Onions (actually any onion will do but green onions stay smaller)
Asparagus
Cucumber
Marigold Bad Companions:
Cabbage Family (including Brocoli, Cauliflower and Brussles Sprouts)
Corn
Fennel
Irish Potato (though potatoes and tomatoes are in the same family, they spend all their time reminiscing and not putting out tomatoes)
Jerusalem Artichokes (herbicidal - but attracts lady bugs) Best Wishes and Happy Holidays :)
Amino-X | 
