A self-watering planter has a bottom reservoir filled with water. The soil wicks moisture from this reservoir up to the plant roots where they need it. While these containers require less manual watering, it is necessary to refill the reservoir at least once a week. There are many commercial versions on the market, but you can create a simple self-watering planter from readily available and inexpensive 5-gallon buckets. This planter is large enough to grow tomatoes and other similar size vegetables.
Set a plastic drinking cup rim side down in the center of the bottom of one bucket. Trace around the cup with a permanent marker. Cut out the traced cup shape from the bottom of the bucket with a jigsaw.
Drill 1/2-inch holes in the bottom around the cutout. Make approximately 16 holes. Drill a single 1-inch-diameter hole in the bottom near the side of the bucket using a hole saw bit on the drill.
Poke holes in the sides of the plastic cup with a pencil. Make approximately 10 holes in the cup.
Set the cup inside the second bucket with the top of the cup facing up. Slide the bucket with the drilled holes into this second bucket until it rests on the cup. Move the cup until it is setting directly beneath the hole you cut out for it.
Fill the cup with a soilless potting mix. Water it until it is moist and add more soil if necessary.
Slide a 3-foot length of 1-inch-diameter PVC pipe into the 1-inch hole drilled in the bucket. This will be the fill tube for the reservoir. Drill a 1/2-inch hole in the side of the outer bucket just beneath where the bottom of the inner bucket is setting to make an overfill drain.
Finish filling the bucket with soil, then sprinkle with water to moisten. Pour water into the PVC pipe until it comes out of the overfill hole.
Sprinkle 1 cup of granular fertilizer on top of the soil around the rim of the bucket. Cover the top with a square of landscape plastic and secure by wrapping a bungee cord around it.
Cut an X in the center of the plastic. Sow your plant through the X to the same depth it was at in its nursery pot. Water via the fill tube and reservoir.