Build a Self-Watering Timber Planter in 9 Steps

Build a self-watering raised bed from treated pine to grow salad greens.

Timber planter

Everyone loves to grow fresh salad greens, tomatoes and herbs.

But backyard crops need regular water to thrive.

Too much or too little can result in problems like rot, wilt and split fruit.

A weekend away can be enough to kill off a thriving veggie patch if there’s no-one around to do the watering.

To avoid the problem of withered crops, build these self-watering timber planters and use them to grow edibles.

Not only do they look good, but they also keep animals at bay and you can leave them for weeks on end without having to worry about water.

How they work

These self-watering planters are also called sub-irrigated planters, or SIPS, because they allow the plants to sip water whenever they want.

Built as a box with posts and a floor attached to joists, the timber used is MGP10, F7, H3 treated pine, as it’s long lasting for outdoor use in exposed situations above ground.

Cut lengths of 70 x 35mm timber in half using a circular saw and fence guide to make the posts.

When the box is ready, add a pond liner to retain water, then position the socked agricultural pipe and fill with soil mix.

The secret to the success of these raised beds lies in the use of the socked agricultural pipe.

Once you fill the agricultural pipe reservoirs, they allow air to circulate and water to wick up to the roots of the plants whenever needed.

Watering plants from below means the roots stay moist and there’s less evaporation, so you don’t need to water as much.

TIP The clear plastic tube allows any overflow water to drain away.

Building the planter step 1: Build the box ends
 Building the planter step 1: Build the box ends
Australian Handyman

Position the end boards on a level workbench, aligning them with the corner to keep the assembly square.

Lay three posts across the boards, one on each end and one in the centre, securing each post with two screws into each board.

2. Make the box sides
2. Make the box sides
Australian Handyman

Position and clamp the side boards on a level workbench, aligning them with the corner to keep the assembly square.

Mark the post locations at 600 and 1200mm from one end.

Position and secure each post with two screws into each board.

3. Assemble the box
3. Assemble the box
Australian Handyman

Stand up the ends and sides on a level surface and align the corners, positioning the ends in between the sides.

Clamp each corner and measure the diagonals to check for square, then secure the corner posts to the sides using screws.

4. Mark the joists
4. Mark the joists
Australian Handyman

Cut a timber block to 340mm long to use as a flooring depth guide.

Position the block against the side of each post inside the box and mark the top of each joist and floor cleat on the sides of the posts using a carpenter’s pencil.

5. Secure the floor
5. Secure the floor
Australian Handyman

Attach the floor cleats to the end posts then secure the joists to the side posts using screws.

Position the floor boards hard against the posts and mark the notches to be cut out with a jigsaw.

Lay the flooring and secure to the joists with decking screws.

6. Attach the pond liner
6. Attach the pond liner
Australian Handyman

Lay the pond liner inside the box, smoothing it across the floor.

Fold the liner neatly at the corners and secure it around the inside top of the box using staples.

Trim off any excess liner flush with the top of the box using scissors or a utility knife.

7. Add the agricultural pipe
7. Add the agricultural pipe
Australian Handyman

Secure the capping with screws, then evenly space three lengths of agricultural pipe in the box.

Wedge the ends tightly against the box and pack soil mix around the pipes to keep them straight.

Cut a hole at one end of an outside pipe for the PVC filler tube.

8. Install the overflow tubing
8. Install the overflow tubing
Australian Handyman

Drill a 12mm diameter hole in the end of the planter box opposite the filler tube just above the height of the agricultural pipe.

Cut a hole in the top of the pipe next to the box hole and position 12mm tubing from the agricultural pipe to the drainage hole.

9. Fill with soil and plants
9. Fill with soil and plants
Australian Handyman

Blend soil in a wheelbarrow to make a lightweight mix.

Shovel the soil into the planter, finishing 25mm below the capping, then fill the pipes with water until it overflows.

Add the plants and mulch, giving the soil surface an initial water.

The Self Watering Planter
The Self Watering Planter
Australian Handyman

An easy-to-follow diagram of how to build this Self Watering Planter.

 
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