Old Milk Cartons... New Self-watering Pots!

[wulf]

Self-watering Recycled Pot by basswulf, on Flickr

This is my latest bit of garden handiwork. It is a series of self watering plant pots made from old milk cartons.

I simply cut them round just below the handle and then inserted the inverted top (lid removed) into the bottom section. A few stones went into the inner section followed by a mix of compost and perlite.

The design gives three ways of watering. I can sprinkle water on top as per normal watering practises. However I can also pour water down the handle (the soil line is below the opening), taking water down to the middle of the container or put water in the outer container, where it will be drawn up through the earth, encouraging the roots to reach down.

Self-watering? Well, perhaps not entirely. However, I can give a good dose of water to the base less frequently than I would need to if watering from the top was the only option. The containers don’t have to stand in a waterproof tray to avoid water loss into the soil and the small spaces at the sides (compared to the relatively large void created the combined shapes) will reduce evaporation.

I only made them last weekend but, so far, the design is working well.

Wulf

[Ellendra]

I've used a similar technique with both milk and soda bottles, and found a few problems that can be prevented if caught early enough.

Problem 1: The cut edges of the plastic are sharp enough that if the stems of the plant so much as touch them, it kills the plant (often severing it completely). This happens most often when moving the plant outside after starting them as seeds indoors. Tape or pad that edge well!

Problem 2: Because the plastic doesn't breathe well, anaerobic fermentation can take hold in the soil. The gases and other byproducts of this fermentation are toxic to most plant life (with a few exceptions, normally found in swamps and bogs). Cut several air holes in the sides of the bottle to prevent this, and stay alert for the smell of methane (most often detectable just after a good watering, as the water pushes some of the gas out).

Problem 3: This one applies only when transplanting, but the soil can stick surprisingly well to the inside of those bottles, so much so that the roots will tear off before the soil will release from the bottle. Cutting the bottle away from the roots only partially works, I still lost large chunks of the root ball. The easiest way to keep it from tearing is, when filling these bottles, first line them with something like a piece of landscaping fabric, with the edges sticking out far enough you can get a good hold of it to pull. (I'm told a double or triple layer of newspaper will work, but I haven't tried that yet.)

Yours look better than mine did, most of mine still have the original labels on!

[wulf]

Thanks for the insights!

Wulf