Answer: A tomato plant will use a lot of water during the summer when it has grown large and is bearing fruit and the weather is hot and/or windy. The bigger it grows in relation to the container, the more water it will need. Sometimes with a container plant this means watering twice a day. You should be able to grow one in a five gallon bucket, although a half whiskey barrel is even better unless you selected a variety that is especially suited to container growing.
Keep a careful watch on the soil moisture. The soil should be evenly moist like a wrung out sponge, not saturated/sopping wet and not dried out. Use your finger to dig into the soil and feel it. If it is still damp, don't water yet but never wait so long that the plant wilts. If the soil alternates too much between wet and dry you will have black spots (blossom end rot) on the bottom of the tomatoes as a result. Container plants will also need regular fertilizing with a slow release and/or water soluble fertilizer. You might also top dress with compost to help provide micronutrients.
Suckers are secondary branches. They tend to be a problem on indeterminate plants because with many suckers on them the vines will grow big and very heavy. They also use up the plant's energy but tend to produce smaller fruit than the main stem of the plant can. With a container plant that is indeterminate you probably will need to prune just to keep it from outgrowing the container and whatever support you have for it to grow on.
You can remove secondary growth easily when it is young, just pinch it off with your fingers. Here is an article about pruning tomatoes that you may find helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Enjoy your tomato plant!
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