Revolutionizing Urban Agriculture, One Sub-Irrigated Planter At A Time

As you may have noticed, Ecocentric bloggers have a soft spot for cool stuff on roofs. I'm certainly no exception. Since visiting Brooklyn Grange during its momentous transformation from tar beach to productive urban farm, I've been obsessed with excited to see additional examples of successful rooftop agriculture. So when a coworker forwarded an invitation to an event at Slippery Slope Farm, I cut out of the office, hopped on the bicycle and pedaled over to Brooklyn at a pace best characterized as maniacal. After ascending sweat-soaked from the sweltering sun-baked streets, I was graciously welcomed to the rooftop oasis featured in the slideshow above.

Owned, constructed and operated by Frieda Lim, Slippery Slope produces an impressive variety of beautiful vegetables using 75 sub-irrigated planters (SIPs). Unlike traditional, in-ground, top-irrigated planting setups, SIPs utilize a standing reservoir of water situated below the soil in which the plants are grown. Despite the fact that these systems are incredibly efficient (and really easy to build and manage), SIP technology remains surprisingly underused and esoteric.

Enter Bob Hyland, sub-irrigation guru, urban ag activist, teacher, visionary. Bob has selflessly assumed the role of SIP publicist/professor, tirelessly sharing his knowledge of sub-irrigation in order to revolutionize urban food production and ultimately create an entire new sector of green jobs. In his spare time, Bob also founded the Center for Urban Greenscaping (CuGreen) and serves as the prolific wordsmith behind Inside Urban Green, an incredibly comprehensive blog about SIPs.

Not surprisingly, Bob was involved with Slippery Slope (he provided Frieda with information and advice when she decided to build her rooftop micro-farm), and was hanging out up on the roof when my colleagues and I visited. Check out the slideshow above to see images of the farm and hear our interviews with Frieda and Bob – they're both tremendously inspirational. Continue reading below to learn why SIPs are so well-suited to urban food production.

Primary benefits of SIPs for urban agriculture:


Perhaps most importantly, SIPs are incredibly efficient – a whopping 50% more productive per square foot than traditional top-irrigated systems. This is hugely beneficial in cities, where demand for produce is great, but open space is often limited.


SIPs are comparatively easy to transport (ever try moving 1.2 million pounds of soil?) The mobility comes in handy when you get a new apartment – or when the lot you've painstakingly planted is unexpectedly reclaimed by its owner or threatened by development.

Contaminant Free!

SIPs eliminate the threat of planting in contaminated soil. Though urban soil isn’t always full of toxins, it’s reassuring to know exactly what your vegetables are growing in.

As Bob would be quick to point out, there are plenty of non-urban-specific advantages of SIP systems as well:


SIPs use as much as 90% less water than top-down irrigation systems.


SIPs are easy to construct, and even easier to maintain. Traditional top-irrigated plants are notoriously susceptible to death by improper moisture levels (usually, too much water is added, eventually causing plant roots to rot). Since SIPs can be built with an overflow drainage hole, the threat of overwatering is eliminated. Even the novice or lifelong black-thumb can easily grow beautiful plants.

Healthier Plants!

SIPs provide a consistent water supply, effective sub aeration, and improved control of nutrients. As a result, it’s easier to grow healthy plants. Apparently, sub-irrigated plants seem to have a higher tolerance for reduced light as well.

Learn more about sub irrigation on Bob’s exceptionally comprehensive blog, Inside Urban Green.