About self-watering planters
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Store water in drain pipes
The drain pipes are filled with water, which is gradually wicked out by the soil and absorbed by the plant roots.
I love to grow fresh salad greens, tomatoes and
herbs. But growing veggies during high summer
means daily watering, which becomes a problem
when we go away for vacation. In the past, we’ve
hired the neighbor kid—sometimes he remembered,
and sometimes we came home to withered veggies.
Last summer I decided to build “self-watering”
veggie planters that I could leave for a week without
watering. The results were amazing. The planter
boxes themselves were gorgeous, they kept rabbits
and other critters from munching on my greens, and
I went for weeks on end without having to water. I
watered three times all summer long (no kidding),
and we had garden-fresh salads until frost. In this
article, I’ll show you how to build one for yourself.
The secret is in the perforated drain pipe.
Self-watering planters are sometimes called
“sub-irrigated planters” or SIPs, because your plants get to
“sip” water whenever they want. Our version uses inexpensive
perforated drain pipe with a fabric sleeve in the
bottom of the planter. Once you fill the drain pipe reservoirs,
they allow air to circulate and water to wick up to
your plants’ roots whenever they need it.
When plants are watered from below, the roots stay
consistently moist, there’s less evaporation and you don’t
need to water as much. The vinyl tubing allows any
overflow water to drain. There are many commercial self-watering
planters available—the EarthBox (earthbox.com) is one but you can easily make your own.
Build a self-watering planter
Top 8 Reasons to Build This Self-Watering Planter
- It saves your back and knees.
- You’ll have fewer weeds.
- It waters your plants while
you’re away.
- It saves water.
- You’ll have fresh veggies
steps from your back door.
- It’s easy to create the
perfect soil.
- It protects your veggies
from hungry critters.
- It’s a handsome addition to your patio.
Self-Watering Planter Basics
- Choose a spot that gets at least six hours of sun. If your planter is
against a wall, you can get by with less sun because of the reflected
heat.
- A 4-ft.-wide planter is ideal for harvesting from both sides. Keep
it to 3 ft. wide if you’re placing your planter against a wall or fence.
- Line your planter with a “fish-safe” rubber membrane. It will prolong
the life of the wood without leaching chemicals into the soil
(and your food). You can buy fish-safe pond liners in different thicknesses
and materials at home centers, garden centers and online
retailers.
- Don’t use garden soil or a heavy potting soil in your raised garden.
Use a light, fluffy “soilless” blend that will retain moisture without
compacting or becoming waterlogged. You can also buy potting
soil specifically formulated for self-watering planters.
- Mulch your containers to keep weeds down and to slow
evaporation.
- For more great ideas for building sub-irrigated planters (SIPs),
visit insideurbangreen.org.
Build your own planting box
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Photo 1: Screw the box ends together
Pick the straightest 2x2s for the corner cleats. Align
the parts with the corner of your worktable to keep the
assembly square.
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Photo 2: Construct the box sides
Straighten bowed boards with a clamp. The top boards
need to be straight so the cap will go on straight and tight.
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Photo 3: Screw the box together
Clamp the edges together and press firmly with the
other hand when screwing each plank so everything comes
together tightly.
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Photo 4: Mark for the decking joists
Determine the floor depth (see “Building Tips”),
and cut a block that length to mark the locations of the
horizontal cleats and joists.
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Photo 5: Attach the joists and lay the floor
Screw the horizontal end cleats in place first and then
the center joists. Notch your deck boards to fit around the
vertical supports.
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Photo 6: Staple the rubber membrane in place
Fold the pond liner at the corners and staple it around
the perimeter. Trim the excess.
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Photo 7: Position the drain pipe and the fill tube
Cut the perforated drain pipe into 6-ft. lengths. Space the drain pipes evenly along the deck floor, wedging the ends tightly against the short sides of the planter to keep soil out. Pack
potting mix around the pipes to keep them straight. Stick a
fill tube in the top end of one of the outside drain pipes. The water will flow from there into the other drain pipes through the perforations in the tubes.
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Photo 8: Drill a drain hole and fit the tubing
In the end of the planter
opposite your fill tube, drill a
drainage hole just above the
height of the pipe. Run vinyl
tubing from the drain pipe to
the drainage hole.
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Drainage hole
Extend the vinyl drainage tubing out the side.
Photos 1 – 6 show you how to build a handsome wood planter
box. The total cost of my 3 x 6-ft. cedar planter was $330. If you
use treated wood, the price would drop to about $250. And I
used a thick EPDM pond liner, which cost $120. (You can buy
thinner versions at home centers for about $35. All the other materials are available at home centers or garden/landscape centers.) To give the box a nice finished look, we routed the boards and sanded the faces and cap. We left the cedar unfinished, but you could seal yours.
After we built the basic box, we moved the planter to its final
position and then added the self-watering system, soil and
plants. Even without the soil and plants, this planter is heavy!
Photos 7 and 8 show you how to construct the self-watering
system. Once you’re ready to plant, add a soilless mix to just
below the top of the planter.
Once your plants are in, fill the drain pipe reservoirs through
the fill tube until water runs out the drainage hole (this can
take a while). The water will slowly wick out of the perforated
pipes into the potting mix packed around it and eventually up
into the potting mix and plant roots above.
You’ll have to experiment to see how long your planter will
stay moist. Fill the drain pipes whenever the soil feels dry 2 or 3
in. down. When I set mine up, I filled the drain pipes and gave
the plants an initial surface watering and then mulched around
them. After that, and despite a record hot summer, I refilled the
pipes only three times over the summer and I had herbs and greens growing until the first frost!
Figure A: Self-watering Planter
Figure A: Self-Watering Planter
Overall dimensions: 3’ x 6’ x 23 1/2"
For Material List, Cutting List, and Plant choices for containers, see Additional Information below.
Note: We notched the flooring to fit
(Photo 5). You can also fit the floor within the
2x2s as shown and let the liner span the gap.
Building Tips
- When assembling the box ends (Photo 1) and sides (Photo
2), leave gaps between the planks to allow for expansion and
contraction. I used 1/16-in. washers as spacers.
- To determine where to put your planter floor (Photo 4), add
together your soil depth, the flooring thickness and the height of
the drain pipe and add an inch to that so the soil level will sit an
inch below the top of the box.
- For greater strength, use 2x2 horizontal cleats (33 in. long for
our planter) for each end and 2x4s for the center two joists.
- Don’t miter the top cap—miter joints open with changes in
humidity. Butt joints will look neater than miter joints over time.
- Wedging the ends of the drain pipe against the planter will
prevent potting mix from getting into the pipes.
- Wedge the CPVC fill tube tightly into the top of the drain pipe. It
should be long enough to poke out of the top of your soil once
your container is planted (Photo 7). You only need one—the water will flow into all the drain pipes.
Video: How to Build a Sub Irrigated Planter System
If you like fresh vegetables and herbs from the garden, but don't think you can have a garden, Elisa Bernick, an editor at The Family Handyman, shows you how to build a sub irrigated planter system (also called a self-watering planter) that will allow you to grow your favorite foods and keep them watered, even while you are on vacation.
