I was debating building a raised bed or two at my parents’ house for a summer garden, but I ultimately decided against it in favor of just building a bunch of sub-irrigated planters.
SIPs are a really neat way to container garden. They’re sometimes referred to as self-watering, but that’s a misnomer: you need to water, just much less frequently than with typical gardening methods. Unlike in most gardens, the water is introduced to the plant from the bottom of the planter by means of capillary action (my favorite!) instead of via surficial watering, as with a hose or a watering can.
Benefits of SIPs:
- They have the capacity to hold large volumes of water without over-watering plants.
- You don’t need to water as frequently. Just fill it up until the planter starts draining from the overflow tube, and you’re good to go for a week or two (depending on capacity and your regional climate). Going away for a week or two, but can’t find someone to come water your garden? No problemo!
- They’re portable; I can start plants that are vulnerable to hard frosts sooner, because I can move the planters inside at night/on colder days.
- The built-in reservoir system gives your plants’ roots access to much needed oxygen, in addition to the water.
They take a bit of effort to throw together, but the payoffs are worth the time invested. It’s a fun weekend project, it’s cheap (read: my SIPs were freeeeee), and your plants will love you.
To make two SIPs, I used:
- drill, 1/4” bit
- box cutter
- Sharpie (to mark a couple of holes)
- bunch of repurposed 32oz seltzer bottles
- 1x 32oz Chobani container
- 2x 5 gallon buckets
- 1x small plastic tote
Photo-heavy tutorial after the break for any interested parties.
I made two types of SIPs. One requires two containers of the same size (in this case, 5 gallon buckets) and one requires only one container. The general concepts are the same, but the execution is a bit different, so I’ll explain them separately, starting with the former.
First, place one of the buckets inside the other. The top bucket will be the planter (i.e., where the plant/soil/potting mix will be), and the bottom bucket is the reservoir (from which your plant will draw water/oxygen). Mark the uppermost part of the reservoir that you can drill a hole without going through the planter. This hole will be where the excess water drains from your planter (overflow hole). You can see in the photo below where the planter ends (thanks, Sun) and where I’ve marked to drill my overflow hole. Go ahead and drill it out, and then remove the planter from the reservoir. We’re done with the reservoir (yay!).
On the bottom of the planter, trace the bottom of the yogurt container (deli containers work great, too), and cut a hole just a wee bit wider than what you’ve traced. You want the yogurt container to fit snugly in the hole of the planter. The yogurt container becomes your wicking basket, and will be the main means of water traveling from the reservoir to the planter and roots of your plant. After you secure a nice fit for the wicking basket, drills holes all over the side and bottom of it, as well as all around the hole of the planter (wicking holes). Finally, trace a hole that will fit the mouth of one of the seltzer bottles near the edge of the bottom of the planter. Drill it out. This is where the water will enter the reservoir from the surface.
In the two pictures below, you can see the reservoir (in the background of the first image, complete with overflow hole), the planter (pre-drilling of the extra wicking holes and the water access hole in the first, work-in-progress in the second), and the wicking basket.
Invert the planter so it’s right-side up again, insert the wicking basket, and then place the planter inside the reservoir. You’re now going to cut the tops off a few seltzer bottles using the box cutter. Remove the caps and fit them together, creating a sort of funnel system, as pictured below.
Now we’re ready for potting mix! With these planters, you want to use potting mix as opposed to potting soil. The mix offers better wicking power, which is necessary in order for the water to travel from the reservoir to the roots of the plants. Take a bunch of potting mix and firmly pack it into the wicking basket.
Once the wicking basket is firmly packed, fill the rest of the planter with mix. There’s no need to pack it firmly. As you can see below, the soil is loose and prepped for a tomato transplant.
The roots of the seedling were quite moist, so I didn’t bother with an initial surface watering, but you’ll want to go ahead and water any seeds that you may sow, because capillary action only works so quickly. Fill that sucker up until water starts coming out of the overflow hole, and we’re good to go!
Done with the first! Onto SIP #2.
In this type of SIP, we use only one container: the planter. The reservoir is internal and is constructed out of plastic bottles. (Depending on the size of your container, you can use plastic half gallon milk jugs, gallon water/milk jugs, et cetera. The larger the planter, the larger the reservoir should be.)
The planter I chose fits 4x 32oz seltzer bottles, which will become the reservoir. Let’s start there. Along one side of each bottle, cut a few slits. This will be the “bottom” side of the reservoir, and is the means for water entering the reservoir. On the opposite side of the bottle, drill a bunch of holes. Like with the wicking basket in the previous SIP, these are the holes from which the soil will draw the water. The image below show a bottle with a few holes drilled (though more were added).
Once you’ve got all of your reservoir containers adequately sliced and drilled, they will look something like this in your planter:
The next step is to drill your overflow hole. While you could just drill a random hole in the side of your planter at the same height of your reservoir (i.e., the height of the bottle as it sits in the planter), this could lead to clogging. Unlike with the previous SIP, the reservoir in this SIP is not entirely separated from the soil, so the overflow hole could get clogged by soil, leading to poor drainage. The best method is to connect a single reservoir to the overflow hole with a tube. In this SIP, I lined up the mouth-piece of one of the seltzer bottles, traced a hole, and cut it out. As you can see below, the overflow hole will drain directly from the reservoir.
Next, created a hole the same size in one of the planters. This will provide an entryway for the water. I chose the bottle opposite of the bottle I used as the overflow reservoir. I did this to ensure that water traveled across the planter and into each reservoir before exiting via the overflow hole (kind of like the failed compartmentalization that doomed the Titanic). Make the same kind of water funneling system that was used in the previous SIP, and insert it into the hole.
There is no need to remove the caps from the bottles or connect them to each other. The water will travel across the bottom of the planter and enter each reservoir through the slits that you created in the bottoms.
Pack potting mix firmly around each reservoir. This will serve the same purpose as the wicking basket in the previous SIP.
Once the reservoirs are firmly ensconced in potting mix, you’re ready to fill the planter up with potting mix. I sowed some seeds directly into this one, so I watered the surface where I planted them. Then I poured water into the SIP until it told me to stop (see: water coming out of the overflow hole).
Annnd that’s that.
Happy SIP gardening!
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- wannakickit said:This looks like brownies. Why does this look like brownies? I want brownies.
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- rookcanrun said:How do these planters work for root vegetables?
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- ariavie said:1.My water bottle looks just like yours and is on the desk right next to where yours appeared on my computer screen. 2.I once used yogurt containers from aspartame and non-aspartame for starter broccoli, nothing grew in the aspartame ones. Scary, no?
- mrsfitwatcher said:New blog handle: runningwithgreenthumbs.
- tallmormon said:I really am interested.
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- gillsquirt said:cool! too much writing. #lazy.
- regainingmymoxy said:If I didn’t have. Ats that would eat it and then barf it back up everywhere I would SO make an urban garden of some kind. Meh - taking care of tge cats is enough.
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