Saturday, April 17, 2010

Making a Cedar Sub-Irrigated Planter

While I can appreciate the practical beauty of our SIPs, they are a special kind of ugly when nothing is growing in them.  And I'm not thrilled about using plastic, no matter how safe it is.

With that in mind, I made two large SIPs out of rough cedar fencing boards.

My journeyman carpentry skills were put to good use; it wasn't a simple project.

The first step was to mill the boards so the long edges were square. Then I glued, and clamped, them up into large panels using biscuits.

The water reservoir is made by lining the box with 4 mil plastic. The soil screen is boards drilled with 1/4" holes that rest on a wood cleat 3" above the bottom of the reservoir. The wicking chambers are strips of plastic cut from a 5 gallon bucket and then turned into small rings.

Each planter measures 70"x16"x14" and holds 6 cubic feet of growing medium. It took roughly 20 hours and $80 in materials to make and install both of them.

I'm about halfway done with a major project to retrofit my existing 30 Rubbermaid tub SIPs. Instead of the plastic bag cover and angular trellis support, I'm cladding them in panels made from inexpensive brown UV resistant tarps and cedar. In addition to looking better, the new design is much more functional. I'll have more to say about the changes in another post.

[Updated 9.25.10 -- There has a been some cupping of the fence boards because of their high moisture content when I bought them.  It's mostly aesthetic, nothing that makes them fall apart. In the future, to avoid this, I'm going to use the more expensive kiln dried cedar.]


H2 said...

Beautiful work, Bruce. Will be eager to see plants flourish in these.

Homegrown Evolution said...

Very cool.

Anonymous said...

Journeyman carpenter is definitely a step above wood shop instructor. Your planters look great.

RVcook said...

I LOVE this idea! Can't wait to hear how they workout and what changes you'll be making next time ;-)


Robj98168 said...

How does the 4 Mill hold up? This could be the answer to the area under my front window!!! Looks nice enough!

Bruce said...

Robj -

Well, it's too soon to tell. I don't see why it shouldn't outlast the cedar. There's nothing that can poke through the 4 mil down in the reservoir. We'll see how it holds up.

I used the 4 mil because I have several rolls in my garage. If it fails I'll buy some 6 mil and try again.

derek said...

Looks great Bruce. Been meaning to try this myself for the last couple years and I'm excited to let you be the guinea pig! It seems to me the only place where leak would be likely to develop would be where the wicking chambers make contact with the plastic. Any shifting of the box might cause it to scrape the lining and tear a hole. I'm wondering if there aren't any Koi pond liners that may be non toxic and more heavy duty for this purpose - but I assume you have already looked into that.

Debbie said...

The boxes look great! I just bought some cedar for my raised beds and read on that you can used linseed oil on the wood to protect it.

... A good alternative would be to use cedar and treat it with a linseed oil finish. You can also use regular wood and treat it with linseed oil. Linseed oil is a natural product and will not give off toxic chemicals into the soil.

knoxruss said...

Bruce -

How did you handle the drain holes for the reservoir?


Bruce said...

Hi knoxruss,

The idea is to pass one piece of tubing through the entire SIP. By drilling little holes in the middle of it, when the water gets too high in the reservoir, it'll exit via the tubing.

The actual drain holes are the same size as the 1/2 black poly that I used as a fill tube. I drilled one on each side, just below the level of the soil screen/shelf.

I cut a length of tubing 4 inches longer than the width of the box. All you'll see from the outside is 2" sticking out from each drain hole. This piece will be passed through the entire SIP. First you'll need to make two small "x's" with a utility knife to let it go through the plastic reservoir.

I drilled 1/8" holes the middle of this short piece of tubing, leaving the parts (on each end) where it would pass through the holes in the wood intact.

It's the last thing to go in. Push/pull it through the 2 holes in the sides of the SIP.

If you look closely, you can see it in the second photo. It is a little black dot, about 3" from the bottom of the SIP and directly below the fill tube.

Debbie said...

Bruce love the planters. I would like to make small version of your cedar planter for growing salad now that fall is here. I am concerned about the 4 mil plastic. I What type did you use?

Bruce said...

Hi Debbie,

I used polyethylene, a relatively "safe" plastic. It also goes by the generic name "Visqueen" at places like Home Depot and Menards.

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