The Sub-Irrigated Planter Project
It’s high time I shared the revelation that’s come to our rooftop garden. This project has been months in the works, and years if you count the work of my consultants on this project, who have dedicated their life’s work to exploring and sharing the virtues of SIPs (sub-irrigated planters). And now that the sun has been beating down hard on the rooftops of Red Hook, these uniquely outfitted keg-containers have proven themselves so much worthy of the effort that was put into them. The plants in SIPs are really outdoing all the others.
Last fall, I became aware of a gardening tip ardently encouraged by a horticulturist named Bob Hyland, of Inside Urban Green. His recommended system for healthy, productive plants in tight quarters such as the city was by sub-irrigation. Essentially, a reservoir is placed at the bottom of a contained soil system, from which moisture wicks up to the roots in the plant, and in turn, the roots reach its depth of hydration as it grows. I wrote about this on Brooklyn Based, and had Bob and Frieda Lim, a Brooklyn rooftop gardener who had enthusiastically subscribed to his work, on my radio show, Let’s Eat In. And of course, they offered to figure out how to outfit the existing converted kegs on my rooftop into sub-irrigated planters.
We spent the good part of two afternoons figuring it out. Unfortunately, when we first created these planters back in the spring of 2010, we’d drilled five large holes in the bottom of each one, in addition to sawing off their tops. This was an obstacle to holding water at the bottom of each planter, the key to SIPs. So we figured out a way to plug up the holes with none other than corks — nature’s impenetrable wood. (Truth be told, many of the holes varied in size, and we had to adjust the corks to be thicker or narrower using duct tape and a straight-edge knife.) Next, we had to create some sort of container that would hold the water in the bottom of each keg. In came some of Bob’s most trusted recyclables — corrugated plastic tubing, used water bottles, and plastic containers of other sorts. Ultimately, we used mostly corrugated plastic piping to create donut-shaped rings that would sit at the bottom of each keg, and made feed tubes that fit snugly into the corrugated tubing made from plastic piping from Loew’s.
In the end, it was definitely a project that owes to the collaboration of many. From our community garden member Shunya, who spent an exhausting afternoon with me pulling apart and cutting holes into the slinky-like plastic tubes to Sarah, who had actually drilled the initial holes into the kegs last spring and had to help in plugging them up this one with corks, it was a group effort. But I’m proud to share that it was well worth the effort. These thirty containers that we had successfully retrofitted as SIPs are growing the most productive and healthy plants on the roof.
There is also a drainage hole on the bottom-side of each keg, where a thin tube was placed in order to drain water so as to not let the soil get water-clogged. This is just above where the reservoir sits; it’s not healthy for plants to have no drainage whatsoever, so this tube solves that. See how the water flows out from it after being watered overhead?
To be honest, there are much easier ways to create SIPs than having to convert these kegs was, we realized. Short, rectangular containers with no holes at the bottom to begin with work much better than having to plug up existing holes, and creating a reservoir that would fit snugly at the base of a round, narrow keg. But it was either that, or saw off the tops of more kegs, and we opted for this version. We’ll see long those corks hold up. So far, though, they’re doing their jobs.
As Bob and Frieda will tell you, those who have consulted on numerous individual SIP garden projects, no system is identical in its parts and outfitting. But the essential idea is the same: the planters have a pool of water from which to gently “sip” from beneath, rather than being dry as a bone at the bottom when not watered quite enough. Plus, the SIPs conserve water, so are more hands-off to work with. They ensure happier, healthier plants thanks to the constant source of moisture from beneath. They also conserve more nutrients in the soil, rather than having to fertilize frequently, because they are a contained system and don’t flush out the way regular (small) containers tend to. All this is good news for the urban gardener. Added bonus: SIPs can be moved around an area, such as a rooftop, without disturbing the plants one bit.
So here’s a nod to that effort from earlier this spring, and I’m looking forward to the tomatoes, peppers and squashes/cucumbers that I planted in those thirty of them. Stay tuned for how they turn out…
Posted: June 27th, 2011 under Gardening.