Tuesday, July 13, 2010

The Planters

Once I decided to grow these vegetables I had to figure how. Living in a south facing, 3rd floor apartment in Berlin City meant that i didn't have a garden, but a sunny balcony and studio window front. In addition to that I had access to an 32 m² Garage rooftop. So I had to figure out the best way to grow large plants in these off ground spaces. My first idea was to plant them in buckets. But what is the best kind of bucket to grow plants in ? After searching the web for about a week I found plenty of different designs, and the one that really stood out for me was a type of planter called SIP ( Sub Irrigated Planter ). SIPs are used by a number of rooftop- / urban-gardeners, especially in the States. The Idea is to create a hollow space in the bottom of the bucket that acts as a water reservoir. The remaining part of the bucket is filled with potting mix. A tube of some sort, filled as well with potting mix, connects the earth with the water from the reservoir. Through this tube the water is drawn by capillary action into the soil compartment where the plant can make use of it. A second, smaller tube is inserted through the soil into the reservoir for refilling. There is an overflow hole on top of the reservoir to prevent overwatering. The roof of the the reservoir has lots of holes in it to allow air into the soil and to provide drainage.  A cup of dry fertilizer is put on top of the soil. The fertilizer slowly seeps into the soil, providing the plant with all the nutrition it needs to thrive. The top of the soil is usually covered with plastic foil to prevent water from evaporating and the fertilizer from getting wet. The plant grows through a small hole in the plastic foil. The roots get air and moisture from below and nutrition from above.

This video from Home Grown Evolution shows you one way of doing it:

If you live in the States it's very easy to build one of these planters, by stacking two standard 5 gallon buckets into each other. The wide rim of the buckets automatically creates a hollow space for the reservoir. But in Germany we don't have these types of buckets. So i had to come up with an alternative design.

I bought 75 32 Liter Buckets, so called Hobbocks from an Ebay auction. They where previously used for transporting gravel on a construction site, but I got them spotlessly clean. The buckets where made of polyethylene (PE) which, along with polypropylene (PP) is one of the "better" plastics. Do not use PVC. If you want to be 100% sure use  only food grade plastic, you can tell by the knife and fork symbol on the bottom of any food grade container. 
I used aluminum blind rivets to create a rim, on which the false bottom could rest. I cut the false bottom out of old pieces of twin wall sheets that where leftover from an construction site.  The watering pipe is made from 4 cm diameter polypropylene drainage pipe, that was leftover from my installation Abyss. I cut them at an 45 degree angle. This allows water to flow freely into the reservoir and it also acts as a sort of funnel for watering. The center tube is made from an 11 cm diameter polypropylene drainage pipe. It also has a rim of aluminum blind rivets that support the false bottom in the center.  The buckets came with lids and aluminum rings to tightly fasten the lid to the bucket. These aluminum rings are perfect for attaching the plastic mulch. The lids will come in handy for winter storage. I plan on posting more detailed instructions on how to make this version of SIP in the near future.

So what's so good about a SIP ? SIPs allow to grow food in places that are not suited for in ground growing, as long as they receive enough sunlight, be it a roof top,  living room, cement slap or on top of contaminated soil.
SIPs are relatively lightweight, so you can also move your garden if necessary. The plants get all they need when they want it: Water, air and nutrition.  You have high control over what the plants grow in, so you can go 100% organic. The reservoir creates a buffer, so you can leave the plants for a few days without watering. Because the plants only take what they need it is also possible to build an automated watering system with siphons that suck water from a bigger reservoir when ever the SIP's water level drops. This way you don't have to water at all (more on that later). There is very little water wasted because the plastic mulch and the fact that its a closed container that is watered from below minimize evaporation and run off.
Whats the drawback of a SIP ? It requires some input, especially the potting mix isn't dirt cheap. But you can lower the costs by using largely recycled materials. It also is an artificial system. I don't think that it can compete, from an ecological standpoint, with growing plants in ground. But if you live in a city and ain't got no ground, it's probably the best way to go.

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