A large deep container - 20 in./50 cm. in diameter and depth & up - is best. Use one container per plant – tomatoes don’t like crowding. Drainage holes are a must & a drip tray helps when watering. Recycled plastic vegetable oil buckets from restaurants are perfect as long as you drill holes in the bottom - use the lids as drip trays. If you use clay pots, keep in mind that the soil will dry out more quickly and you may need to water twice a day. Put a 2 in./5 cm. layer of clay pot shards, gravel or recycled packing peanuts in the bottom of each container, to ensure good drainage. Use a well-drained organic potting soil or a mix of one part soil, one part sand and one part compost.
Locate your tomatoes where they will get at least six hours of sunlight per day. A sheltered spot is best as high winds can break the plants once they start to carry fruit. If you're on a high, windy balcony, make sure to stake them well and screen them with sturdier plants so they don’t dry out quickly. Tomatoes are classified by the way in which they grow. "Indeterminate" varieties of tomatoes can grow up to 5 feet or more and will require staking. "Determinate" varieties are bush-form and usually stay under 3 feet in height and width. Most heirloom varieties are indeterminate. You can use tomato cages if you like but bamboo stakes, left-over doweling or old hockey sticks and garden twine work just as well.
Suckers will need to be removed regularly so the tomatoes stop making new leaves and start producing fruit. Suckers are new shoots that grow out of the joints between the stem and the main leaves. You can gently pinch them off with your fingers or use hand pruners for larger suckers. Be careful not to damage the main stem. (If you're a smoker, wash your hands before handling tomato plants. Tobacco & tomatoes are susceptible to the same viruses.)
Use an organic starter fertilizer - 10-52-10 or similar, with the middle number being the highest - when you first transfer tomato seedlings or starter plants into containers. In hot weather you may need to water daily - the leaves will start to wilt and droop when the plant needs water. Morning watering is best - watering in the evening can promote diseases. Always use lukewarm water – cold water will shock the plants and slow their growth.
Once your plants have gained some height, begin fertilizing to promote fruit formation using an organic fertilizer with an N-P-K ratio of 1-1-4 or 4-7-10. Make sure the first number, which indicates nitrogen (N), is lower than the other two, which stand for phosphorus (P) and potassium (K). Don't fertilize with fish emulsion - at 10-5-0, it’s much too high in nitrogen for tomatoes, and will result in lots of leaves but few fruits. It also contains no potassium, which tomatoes need to fight off disease. Tomatoes are heavy feeders and may need to be fertilized once every week. If the leaves have a yellowish cast or if few blossoms or fruits have formed, the plants need fertilizer.