DIY: Self-Watering Containers and Passive Solar Shading

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Our home is oriented just shy of due South, on a sunny, exposed slope. It’s great in the winter, as many clear, cold days we don’t have to light a fire as the sun provides enough heat. In June & July our house stays cool thanks to strawbale insulation and wood awnings that provide shade above our South windows. But when the sun sinks lower in August, it sneaks beneath the shades, hits the thermal mass of our clay adobe floors, and the house heats up.

The deck in front of these windows also gets direct sun and it gets so hot that any potted plants need watering twice daily and eventually dry out enough times that they don’t re-absorb moisture. I love hanging baskets and containers, but I’m not very good at keeping up with daily watering. Our first summer in this house we rarely spent time on the deck because of the exposure, and often left the house in late-summer afternoons when it got too hot.

The solution to this problem was cheap and easy:  self-watering containers. These are large-volume planters that have a built-in water reservoir in the base that only needs filling periodically. The plants growing in the container send roots down into a wicking basket in this reservoir so that they can access water whenever they need. Having gardened the past 15 years as a transient renter with no ground of my own, improvised portable containers have been a vital part of growing my own food.

Last year I built eight of these containers with materials we scored at garage sales and thrift stores. Lining the South side of our deck, the containers grew 12-foot tall scarlet runner beans, sunflowers, and indeterminate tomatoes that, by August, connected with our wooden awnings and provided full shade to our house. On average I watered these containers once a week, even during stretches of continuous 30+ degree days. The bonus of these planters is that the scarlet runner flowers brought hummingbirds, bees, and butterflies outside our window the full season through, which was daily entertainment for us and continuous forage for them.

Self-watering containers are a great project if you have a balcony or limited space where you want to create more vertical growing area. They can be made out of a variety of items so feel free to take this concept and make it your own with what you have available. Here are the materials that I used:

  • large rubbermaid tote
  • tote lid
  • 4-6 sturdy yogurt containers
  • 1.5″ wide pvc pipe, slightly longer than tote height
  • 1 gallon round plant pot
  • 3 litres of peat, coir, raw wool or other water-absorbing material
  • small piece hardware cloth or burlap, slightly larger than size of tote lid
  • Drill with 1/2″ pilot bit
  • Keyhole hand saw, or utility knife and some muscle
  • Potting mix amended with extra compost and some garden soil

Step 1: Prepare the Lid and Pipe

Drill holes around the lid for drainage. Take the 1 gallon plant pot and trace a the bottom of the pot in the centre of the lid. Use the drill to make a line of holes big enough to fit your keyhole saw or utility knife. Saw around the traced circle to make a hole. Saw around the edge of the lid, removing the lip so that the lid fits inside the tote about 5″ from the bottom. Cut a small hole in one corner of the lid to fit the PVC pipe. Drill a few holes into the bottom 4 inches of the PVC pipe.

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Step 2: Prepare the Base

Turn the tote on it’s side and drill one or two overflow-holes on one wall, 4″ above the bottom of the container. Turn the tote upright again. Take 4 – 6 sturdy plastic yogurt containers and drill a few holes on the bottoms and sides to allow water to flow through them. Place in the base of the tote, leaving room in the middle for the 1 gallon plant pot.

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Step 3: Assemble Base

Place the lid over top of the yogurt containers. Fit the pvc pipe into the hole in the corner, with perforated side down. Place the 1 gal plant pot into the hole in the centre and fill with wicking material such as peat or coir. I had a bunch of sheep wool on hand so filled with that.

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Step 4: Add Soil

Place the burlap or landscape fabric over the base, cutting a hole over the 1 gallon pot to open that area. Begin packing in soil so that it fits snugly around the edges and doesn’t fall into the cracks and fill the reservoir. Continue filling tote until 2″ from top rim.

Purchased potting mix made for containers works well as it can absorb and hold water better than some other blends. It’s a good idea to amend with extra compost, worm castings, or aged manure (I did about 15% total volume in extra organic matter). Adding some garden soil, azomite, endomycorrhizal inoculant, glacial rock dust, and/or slow-release organic fertilizer are optional, but will help provide nutrients if you are planting heavy-feeding crops like cucumbers or tomatoes. Watch the leaves for nutrient deficiencies as the season progresses, and giving liquid seaweed or fish later in the summer might be necessary.

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Step 5: Plant!

At this stage, move the pot to it’s final location so it doesn’t break your back to move it after being watered. To maximize space, plant taller, climbing plants along the back such as pole beans, peas, vining tomatoes, cucumbers, amaranth, sunflowers, etc. Plant the front or edges in herbs, greens, or edible flowers such as calendula, nasturtium, and marigold. If you want something ornamental, trailing flowers such as alyssum, lobelia, or forget-me-nots will help conceal the container once established. Place the container against a sunny wall or fence where you can provide some kind of support for the tall crops to grow up.

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Water the container by soaking the soil medium thoroughly until water begins to come out the overflow holes on the sides. In the future you can either water the soil this way, or fill the reservoir through the pvc tube. Keep the pvc pipe at the front where you can easily access it and fit it with a hose.

These simple, cheap, re-purposed containers aren’t exactly pretty, but they are very functional. I made a few additional ones out of 5 gallon buckets that also worked great. If you want to make them more attractive you can always build a wooden box around them. Larger containers such as a 55 gallon barrel could make a great container for a dwarf fruit tree. Even old bathtubs, hot tubs, whatever free watertight vessels you can get your hands on can be adapted to use this concept.

If you have ground space outside your south windows, it opens up a lot of possibilities for other shading perennials, such as hops, honeysuckle, maypop, grape, and kiwi, as these either die back or drop their leaves so as to not block your winter sun. Having a comfortable living space and somewhere to retreat during summer heat waves is essential. Make shade while the sun shines!

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Late June, before the beans grew up
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Scarlet Runners consume the house, making the deck a nice place to be on even the hottest days

Enjoy the planning and dreaming of spring. Let me know if you try this project and how it goes. Happy Gardening!




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