Planter box, sub-irrigated

Sub-irrigated planter box on wheels

Our yard isn’t ideal for growing. In the morning, the house casts a shadow. On a sunny day, the awning that keeps our sun porch from boiling casts a shadow. The tree casts a shadow in the afternoon. The grill stands in the way of conveniently working on one strip. So if I wanted the kids to enjoy gardening, I needed something accessible and sunny.

Enter the planter box. After plenty of reading and research, I found AlboPepper’s sub-irrigated planter, 30 minutes of clear instructions and a system that was self-contained. (Most others stood on soil, which I didn’t want, given that our lawn is so small the kids can barely play ball on it.)

I planned to modify his plan to include caster wheels to make the box movable on our patio, and the size of my box would be that of the standard European shipping pallet, 80 by 120 cm (32 by 48 inches). Getting the shipping pallet with frame was the easiest part: I got it used for 6 francs. And then it sat in our sun porch for a long time…

Finally, I sat down and did math, calculating the total length of my 10 cm corrugated drainage pipe and the total volume of soil I’d need, as well as the dimensions of the pond liner that would keep the wood from getting wet. I purchased those supplies along with the wheels (picked to support the weight I’d calculated), struts, and screws. It was hard to translate the soil components into German, so I’m still not sure my planter box wicks the moisture up as intended, but 2019 has been rainy, which means the jury’s still out.

And then, I got busy building.

JAS helping saw the bottom
JAS helps me cut a cupboard backing to size

The pallet has holes, so I repurposed cupboard backing I no longer needed (the cupboard had also seen a makeover) to spread the load and keep the pond liner from stretching.

The cupboard backing nailed to the pallet.
The girls playing with leftover cupboard backing and corrugated slotted drainage pipe.
Jam session on the pallet. Cupboard backing still holding up, although I had to bang a few nails back in.
Screwing on the caster wheels early was a life-saver and helped me move the box around much more easily. Here I have clamped a strut in place to pre-drill and then attach with screws. (After taking this picture, I undid the clamp before screwing down the strut…)
The view from above, all struts affixed.
Here’s where some luck came in: the overflow drainage hole fit nicely between strut and metal pallet frame corner.
In goes the pond liner. This process was like making a bed inside-out.
I used masking tape to hold down the liner. It was a bit larger than planned, which meant I couldn’t fold it according to AlboPepper’s instructions. You can see I tried to fold a triangle and lay it to one side of the corner, but that only works if the pond liner doesn’t rise above the edge of the planter box.
Enter origami! Squish a smaller triangle to either side and the flap folds over the edge at the corner, even keeping the triangles from coming undone.
A close-up of the origami solution, stapled down on the outside.
Inside close-up. It doesn’t lie fully flat, but close enough.
I used “Unkrautvlies” to cover the drainage pipe ends. It’s not terribly strong, but I figure it doesn’t need to be.
First pipes are in. It was hard work to get them straightened.
After some filing and plastic cutting, the overflow tube is in! It’s rubber tubing from an old shower hose.
The marking on the short tube is there so the slit in the fabric lines up with the rubber tube.
AlboPepper put the irrigation hole in a corner. I wanted it in the middle because that way it would be least likely to get in the way of the kids, who were going to get a quadrant each.
I drilled holes into a plastic IKEA kiddie table leg.
Now the hollow leg serves as a water inlet. Luck strikes again: the garden hose is just a touch smaller and will stay in there even with the water on.
In goes dirt and mulch and fertilizer and perlite.
Ta-da! Later I sawed the corner off the plastic kiddie table so the inlet got a screw top to keep airborne junk and gunk out.
No sooner had we planted the seeds that we needed to cover it up with a trash bag. Snow in May? Really?
And this is what it looks like mid-June. One advantage of being on wheels is that it’s pretty hard for snails to get in.

4 thoughts on “Sub-irrigated planter box on wheels

    1. thduggie Post author

      We’re not actually rolling it around much, if at all. But we could. Well, I could, or the kids maybe if they all push together. It’s a heavy beast. As I recall, around 900 pounds.

    1. thduggie Post author

      I didn’t post how the boys ran a marble track from the tree with the drainage pipe. Prep was fun, and so far watching stuff grow is fun, too. I think the kids will also learn that planting too much can be counterproductive. We’ll see!


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