I got this idea from Larry Hall, who made a video showing how he uses gutters as self watering containers. In the first part of the video Larry shows how to use a gutter to supply water to a row of pots. In the second part he shows a two gutter strawberry growing system. I decided to build Hall’s self-irrigating gutter (let’s call it a SIG) to grow strawberries. Here’s how I did it:
With some scrap wood I made a support system for the two gutters–one gutter holds water and the other holds soil. I sealed the ends of the two gutters with silicon putty and secured the gutters to the wooden support with screws.
Next came my first trip to a hydroponics shop (there’s one on every corner in Los Angeles), to get a float valve. The float valve, similar to the one in your toilet, automatically fills the lower gutter with water as needed. I tried to fit the float valve through the end of the gutter but this kind of DIY bulkhead fitting is difficult to pull off. I ended up mounting the float valve above the gutter with a pipe strap, as you can see in the photo above. I cut the upper gutter around 10 inches shorter than the lower one so that I could access and maintain the float valve.
The second item I picked up at the hydroponics shop was a bunch of 3 inch mesh pots. These hang down into the lower gutter and wick water up into the soil. I cut circular holes in the upper gutter using a hole saw, and fit the mesh cups into the holes.
Next I filled the upper gutter with potting mix (note that with self watering containers you have to use potting mix, not regular soil). And all self watering containers need mulch of some kind–I just happened to have a roll of vinyl billboard material that my neighbor Ray gave me. I stapled the vinyl to the wooden gutter support and stretched it over the top of the soil. I cut holes and planted my strawberries about 8 inches apart.
The float valve is connected to a rainwater barrel. You can read more about how this barrel is constructed in one of our older posts. Since SIGs need to be watered even when it’s raining, this is a perfect use for a rain barrel. I will have to fill the barrel with municipal water during our dry season.
There’s a lot of plastic here, specifically PVC, which is an environmental and health disaster. I have two questions–how much PVC is leached into the growing medium and how much of it would be taken up into the fruit? I don’t have an answer to either. If you know of science-based information (i.e. not Livestrong articles) on PVC and growing food please leave a link. Generally, plants do not take up toxins into fruit so I’m not losing any sleep thinking about eating a few strawberries grown in my small PVC SIG. I might think twice about eating greens grown in PVC.
The other issue is the use of peat moss as the growing medium. Peat moss is unsustainably harvested (see Horticulture professor Linda Chalker-Scott’s article on this). Coconut coir, in my experience works great, but not in self watering containers. If you know of a peat moss alternative for self-watering containers, please comment.
There might also be mosquito problems with the standing water in the lower gutter. This could be countered with a mosquito dunk.
I can now grow food in an otherwise useless space–the top retaining wall in our front yard (we live on a hill). I can also, finally, make good use of my rain barrel. I was also able to recycle a bunch of scrap wood and some billboard material. And, unlike hydroponics, no electricity or liquid fertilizers are needed. If this system works out I’m eying the top of our garage for more SIGs (our garage is at street level below the house–we look down on it from our front porch).
I think there’s also an opportunity for an entrepreneur to make a non-PVC version this gadget out of food grade material such as HDPE. With a custom design you could also enlarge the upper, soil container gutter as well as creating a sealed mosquito proof lower container. But you would have to sort out who owns the patent on self-watering containers.
And many thanks to Larry Hall for sharing this cool idea!
UPDATE 4/30/2013: One side of the strawberry gutter sprung a leak due to a poor seal on the end of the gutter. I was able to fix it. One thought about the design is that you should leave both ends open and the gutter ends accessible so that you can make repairs. And make sure to use a sealant appropriate for gutters.