Choose a place to hang the tomato planter. Tomatoes need at least eight hours of sunlight a day to produce good fruit. The planter will be heavy, so make sure the hanging hook is anchored well in strong material, or consider using a plant hanger designed for heavy containers.
Use a 5-gallon bucket with a lid. You can buy a bucket at a hardware store, and many restaurants give away used food buckets. Clean the bucket well with soap and water before using it for a tomato plant to kill any bacteria.
Drill holes in the center of the bottom of the bucket and the center of the lid with a drill that has a 2-inch hole saw attachment.
Turn the bucket upright and over the hole in the bottom with a porous material like landscaping fabric. Cut a 2-inch slit in the fabric. This is the hole the tomato plant will come out of when you hang the bucket.
Fill the bucket to the top with a good potting mix. Tomatoes need rich soil that drains well, so consider mixes that use peat or compost.
Lay a coffee filter on the center of the soil and snap the lid onto the bucket. You'll use this hole to water the tomatoes when the bucket is hanging.
Turn the bucket upside down to plant the tomato. Use a healthy tomato start that has two or three sets of true leaves. Cherry tomato varieties like Sweet 100 grow well in pots, as well as Celebrity and Roma plants.
Dig a hole under the landscaping fabric to place the tomato seedling into. The hole should be deeper than the root ball of the start because tomatoes do better when planted with an inch or two of the main stem under the soil.
Remove the tomato start from its pot and place it in the hole, taking care not to disturb the delicate roots. Fill in the hole with soil and tamp it down around the stem. Add some nitrogen fertilizer like fish emulsion or worm castings to feed the roots and protect them from the shock of transplanting, and water it in well.
Leave the bucket with the tomato on the ground for a week or two before hanging it. The roots need a chance to establish themselves before hanging upside down, and the plant should be showing good growth.
Hang the bucket when the tomato plant is about a foot tall. Water the plant daily through the hole in the top because tomatoes in containers need constant moisture. Tomatoes have high nutritional requirements, so fertilize the plant every two weeks with a fertilizer that has an even balance of nitrogen, potassium and phosphate.