
Update March 23, 2010: The top photos construction will work, but this more recent version would be even more simple to make. It will work in any watertight container. Check out this post: The laptop of fresh food.
The do-it-yourself sub-irrigated planter (SIP) (erroneously called "self-watering" in the retail market) is a configuration (top photos) from the Rooftop Gardens Project in Montreal. I made it using only a box cutter except for using a drill motor to drill a drain hole in the side. You could easily make the hole with a hot poker if you don’t have a drill.
The material is expanded polystyrene panel foam insulation (often erroneously called Styrofoam) just like the tomato plant cell pack on the right. The panel foam came in a package of six (6) 3/4"x13 5/8"x48" "boards". That's enough to make six or more grow boxes of this size.
Note that I since realized that the Rooftop Gardens Project SIP grid is made from recycled plastic signs (ex. political campaign or real estate signs).
The support grid forms 9 spaces. You can see that the 4 in the corners are left open. These are filled with tamped down potting mix and create 4 "soil wicks". The other 5 spaces under the support platform form the water reservoir. You simply add water through the fill tube until a small amount flows from the overflow drain hole and then you know the reservoir is full.
Rooftop Garden Project - Old design - New design


The box is a 14 gallon, (23.9x15.9x12.2 in.) bronze Rubbermaid Roughneck tote box. The next time I would use the same type box only in the 18-gallon size (23.9x15.9x16 in). This would increase the water reservoir capacity. Keep in mind that this will also increase the overall weight when full.
The fill-tube is 1" inside diameter vinyl tubing.
A Richly Deserved Award
In my opinion, there's no organization more deserving of an award like this. The Rooftop Garden Project is in a class by itself. Congratulations!
Posted by Greenscaper on July 07, 2008 at 08:09 PM in Container Gardening, Editorial Comment, Education, Rooftop Garden, Rooftop Garden Project - Montreal, Rooftop Gardening, SIP Tote Boxes, SIPs: Sub-irrigation aka self-watering, Urban Agriculture | Permalink | Comments (0) | TrackBack (0)