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How to build sub-irrigated raised garden beds in 12-steps

sub-irrigated raised garden beds

My garden pictured above is a 4x12 foot bed. I've set up two side by side. More photos can be found on Flickr

Step 1: Plan your space and bed size, my supply list will reflect my project size.
sub-irrigated raised garden bed supplies
Step 2: Gather this list of supplies:
Step 3: Saw wood pieces to set up bed frames (I used a mitre saw)
sub-irrigated raised garden bed corners
Step 4: Slip in the lumber to the brace corners and check that area is level. Adjust. Use stone pavers as needed to level.
Step 5: Reinforce the midspan of the 12-foot section with a stake to reduce wood warping.

Step 6: Fill bottom of bed with dirt or sand to LEVEL floor of bed. Check with a level all over floor.

Note: The base of the bed needs to be level so that the water will not pool to any one area.

sub-irrigated raised garden bed plastic lining
Step 7: Line entire bed with one sheet of plastic up the sides as well.

Use electric staple gun to attache to upper rim of box. Important: Do not poke holes in this plastic anywhere below 3-inches above the floor of the bed or the system will leak.

sub-irrigated raised garden bed flex drains
Step 8: Lay six flex drains into the bed
Step 9: Cut Landscape fabric to fit over all tubes with enough slack to touch the floor between each tube.

Note: This step is to keep the roots from growing inside of the tubes so that it's easy to clean up for the following year.

sub-irrigated raised garden bed fill tube
Step 10: Install fill tube into one of the flex with a seal (use a piece of bike tubing to seal it in)
sub-irrigated raised garden bed overflow tube

Install the overflow tube at the end opposite of the water filling side.

sub-irrigated raised garden overflow sub-irrigated raised garden bed tubes
Step 11: Fill bed with garden soil.

Note: At this point you could put 1/3 of the dirt in and then fill with water to see it in action.

Step 12: Stand back and admire, plant seeds & water as needed.
Key items to understand about this system:

You need to leave some room between the pipes so the soil comes in contact with the water. Make sure you pack the soil down between the pipes, as the soil acts as a wick for the water - capillary action.

The purpose of the pipe is two-fold. It transfers the water throughout the bed and as the soil wicks up the water the pipe provides a space for oxygen.

This project rooted from inspiration from a trip to Denmark where I saw a gardening trend with a foam, store bought system, I went on to research the concept and find a system that I could contstruct at home. Time home sick with a cold in February from work, was time well spent!

If this is all looking like too big of a project or too expensive, try a smaller commercially made self-watering planter. or a conversion kit

I am following the great research done by Johanne Daoust, who was kind enough to post her process on Flickr. One other great system to check out for those who want to keep containers individually self watered, should look at the self-watering rain gutter system.

Keywords: Semi-Hydroponic sub-irrigated SIP self-watering

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