We create our rooftop vegetable gardens using sub-irrigated planters (SIP) built from two 5-gallon buckets. Here’s how we make them:

Downloadable Instructions (PDF)

Materials Required:

• Two 5-gallon buckets
• 2 feet of 1 inch PVC pipe
• 18 oz. disposable cup (the wick)
• 30 quarts of saturated potting soil
• 2 cups of fertilizer
• 1 cup dolomitic lime
• ½ white trash bag (the cover)

Tools Required:

• Electric drill
• ¼” pilot drill bit
• 1 ⅜” hole saw
• 3 ½” hole saw
• Hack saw
• Box cutter

Top Bucket
This container will hold the soil, fertilizer, lime, and the actual plant.
1.  Take one 5-gallon bucket and turn it upside down. Using the 3½” hole saw, drill a hole in the middle of the bottom of the bucket. This will serve as the holster for the wick.
2.  Next, using the 1 ⅜” hole saw, drill a hole near the edge of the bottom of the same bucket. This will be used to hold the PVC pipe, or the water tube.
3.  Using the ¼” drill bit, drill 20-30 holes around the entire bottom of the bucket.  These holes allow for proper drainage and aeration of the soil.

Bottom Bucket
This container will serve as the water reservoir.
4.  Take the top bucket and place it in the bottom bucket.  You will see free space at the bottom of the bucket.  The larger the space, the larger your water reservoir.
5.  Next, using ¼” drill bit, drill four drainage holes on the sides, approximately 1” below the bottom of the top bucket.  These drainage holes allow aeration of the soil and make it impossible to overwater the plant.

Putting it all together
6.  Using a hack saw, take the PVC pipe and cut a 45° angle at one end of the pipe.  This will prevent the water tube from clogging over the course of the growing season. Place the pipe in the 1 ⅜” hole.
7.  Next, take a box cutter, cut four slits down the sides of the 18 oz. disposable cup (the wick), densely pack it with the wet potting mix and place it in the 3½” hole of the top bucket.  The cup will dip into the water reservoir, wicking the water upwards.  
8.  Begin filling the rest of the bucket with the potting mix, periodically pressing down the mix in the center of the bucket.  This will help with the wicking process.  
9.  Once the bucket is about two-thirds full, apply the lime and mix several inches dip.  
10.  Continue to fill the container with potting mix until about 2” from the top.  Pour the 2 cups of fertilizer in a ring around the edge of the bucket, not in the center, which will prevent “root burn.”
11.  Finish adding potting mix to make a small mound over the top of the bucket.  
12.  Secure trash bag over the bucket using a rope or twine and cut an “X” in the middle.
13.  Remove enough soil to adequately bury the plant.  Plant the seedling and fill the reservoir.