How to Make a Two Bucket Sub-Irrigated Planter (SIP)

This is a simple, easy-to-do project that will let you grow your own food wherever there’s enough sunlight--on your roof, balcony, back steps, driveway, or vacant lot next door. It doesn't take any special skill and the materials are all readily available. A diagram showing what's going on inside a SIP is here. The fundamentals are the same whether you use buckets, tubs, or Earthboxes.

Once you make one, it will produce beautiful food for years to come. You'll decide that one (or four, or six) isn't enough and you'll want to build lots more. This year we expanded with the ten extras at left.

Many of the photos here are from this second SIP run on the roof, and the pretty yellow pickle buckets are courtesy of Bruce's neighbor who drives for Chicago’s own Vienna Beef (Thanks, Rey! We owe you some tomatoes).

While these instructions are full of details, what you want (a healthy, productive plant) doesn't depend on following them exactly. It doesn't need to be perfect. The holes you cut can be raggedy and you'll still get pounds of tomatoes from one plant. Just try it. And if you get better results by doing it differently, we'd love to hear about it.

Materials and Tools Needed

Two 5-gallon food grade buckets

One 1" diameter watering tube, about 3" longer than the height of one of the buckets, made of safe(r) plastic, copper, or bamboo

One 16-oz or 24-oz safe plastic drinking cup
One 13-gallon plastic trash bag
One cubic foot potting mix (not soil)
Organic fertilizer (1.5 to 2 cups per bucket)
For tomatoes only, Hydrated lime (one cup per bucket mixed into top 6 inches of soil)

Electric or cordless drill
1/4 3/8 inch drill bit
Box cutter/utility knife
Snips or heavy duty scissors

If you've got hole saws it's far easier to cut the two big holes. If you don't have them, you'll just have to do a bit more work.

View this quick video for a sense of how the whole thing comes together.

While it's obviously sped up, it helps to see one done before you try it yourself. Plus, we like the drums.



So now you're ready to make one.

This is the fun part. You get to drill lots of holes in one of the buckets (set one bucket aside and don't drill it):

• a big hole that will receive the soil wicking cup

• a medium-size hole for the feeding tube

• about 30 quarter-inch drainage holes

Because every combination of buckets and cups is slightly different, take a few simple measurements to figure out how big a hole to drill for the wicking chamber. Here's how to do that:

Set the nestled buckets in front of a light source and note how tall your water reservoir is going to be. You need to measure the height of that reservoir. Transfer that measurement to the side of your plastic drinking cup, starting from the bottom. You should now have the height of the reservoir transfered to the side of your cup. Measure the diameter of the cup at that height and add 1/8". That's how big a hole you need to cut out of the bottom of your bucket.

Turn the bucket over and mark the center. Drill a hole for the wicking cup in the center, as I'm doing here at right. If you don't have a hole saw, draw the proper diameter hole on the bucket and drill a series of quarter-inch starter holes around the perimeter of the hole you want to cut out. You should be able to get your snips or scissors in the starter holes and then cut out the larger hole for the plastic drinking cup.



Measure the diameter of your watering tube. Add 1/8" and draw a circle of that diameter about 1" in from the outside edge of the bottom of the bucket. Cut out that hole using a hole saw or with your 1/4" bit and utility knife.




It doesn't matter if the edges are ragged or if there's a gap of a 1/4" or so around either the feed tube or the plastic cup/wicking chamber. You just want to keep the potting mix from falling into, and clogging up, your water reservoir.



Now drill 30 or so 1/4" holes, evenly spaced, around the bottom of the bucket. These are the holes that allow air to get to the bottom of the roots and also for roots to grow down into the reservoir.

You'll want to cut off one end of the feeding tube at a 45 degree angle so when it's sitting in the bucket it won't get clogged up.





Using your utility knife, make 4 vertical slits (evenly spaced, with one in every quadrant) in the sides of the plastic cup. Don't cut through the bottom or the lip of the cup, just the sides. After you fill the cup with wet potting mix (creating a "wick"), these cuts will let water travel from the reservoir up into the potting mix in the upper bucket.

Put the bucket that's full of holes inside the other untouched bucket. As you did earlier, hold the bucket set up to the light and visualize the water reservoir at bottom. This time you want to drill two 1/4" overflow holes, on opposite sides of the previously untouched outside bucket. You want the height of these holes to be about a quarter inch below the bottom of the inside bucket. This means the bottom of the soil bucket will always stay relatively dry, as excess water will run out the overflow holes instead of forcing the roots to stay permanently drenched.


And now you’re ready to plant.

With one bucket sitting inside the other, drop the angled end of the feed tube into the hole you drilled for it. Pack the plastic cup with wet potting mix and set it inside the large hole in the center. It doesn't matter if it sticks up into the potting mix chamber--it's going to get covered up with potting mix anyway.

Fill the soil chamber with lightly moistened potting mix, pressing down every so often so it’s fairly compacted before adding more mix on top. You may want to mix a half cup of organic fertilizer into the potting mix. If you’re growing tomatoes, mix a cup of hydrated lime into the top 6 inches of potting mix. Be sure you have completely filled the bucket with potting mix and pressed it down around the edges at the top. There should be no depression in the soil--rather, it should mound up just a bit at the top.

Sometimes it’s easier to plant larger seedlings by filling the bucket three quarters full of potting mix, planting the seedling, and topping off the bucket with potting mix. Then add the fertilizer ring (see below) and place the plastic over the bucket, gently weaving the plant top and the watering tube through two slits you made in the plastic.




Put one cup of fertilizer around the outside edge of the bucket, leaving as large a space of plain soil in the middle as possible. Put the plastic bag (or clear plastic, as shown here) over the top to keep the fertilizer dry, moisture from evaporating, and UV rays from eating the bucket. Secure with a ziptie or string, cut your hole or holes and you’re reading to plant a small seedling or seeds.

The bucket on the right is ready to be planted with Fin de Bagnol beans, from Seed Savers.



After you plant the seeds (or seedlings), you'll want to water it in from the top. This is the first and only time you'll top water. Pour some water on it to help get it started and ease the shock of transplant). From then on you'll water your bucket by using the fill tube.

You'll be able to see the water level in the reservoir if you look closely. When it gets low, fill it up until water comes out of the overflow holes. Don't worry, you can't overwater it. You can underwater it though, so every few days take a look at the reservoir. When your plants grow larger, you may have to water every day.

Here are a couple more links with tips on planting and growing to get you off to a good start.


If you've got a bunch to do, grab a friend. It's just a bucket!

Look what you can grow