It’s been more than two months since I’ve written anything about the Dinette rooftop garden. Why the wait? Getting two container gardens of equal size ready for production at Dinette and at home has kept me very busy!
And what is this well-watered machine I’m talking about? It’s the essence of an efficient container garden. In my first garden note I focused on the most important requirement for a successful vegetable garden–unobstructed sunlight. That’s based on location. The containers must be in the right spot, because there’s no cheap substitute for sunlight energy.
But a close second requirement is always having water available when the plants want a drink. For that we started out by adding a faucet on the roof of Dinette. But then I had to construct a watering system. That takes a lot of extra time until you get it right.
The Dinette rooftop garden is comprised of 52 individual containers–3.5 gallon, 5 gallon, and 6 gallon food-grade plastic buckets–sized for the type of plant growing in them. But in truth each container is two buckets, one sitting inside the other. The top one holds the soil and the plant, and the bottom one is deep enough to provide a water reservoir.
Now think! How many times have you been unsure whether you’ve watered a plant too little or too much? Having a reservoir under the bucket holding the plant and connecting the top and bottom buckets with a polyester wick allows the plants’ roots to regulate the water supply. As the roots take in more water, the soil dries out, but more water comes up the wick thanks to gravity-defying capillary action.
The trick, of course, is keeping the reservoirs from running dry. Filling 52 container reservoirs once or twice a day is quite a chore. But at the Dinette rooftop garden, like the vegetable garden on my deck at home, the water is distributed through 1/2-inch and 1/4-inch plastic tubes. And to make sure the reservoirs are filled often enough (even when I’m out of town), I’ve installed automatic watering timers, which can add water as often as three times every 24 hours to two different halves of the garden. Not all plants drink water at the same rate.
So what took so much time? Both plumbing and soil preparation. If you think this through, there are at least 52 connections that I want water tight and the tubes long enough so they won’t be inadvertently kicked out or pop out of the reservoirs under pressure. In addition, an equal amount of time is spent getting the soil mixture just right. Because these are containers, we use a lighter mixture of soil than you would in a regular home garden. The combination of peat moss, compost, vermiculite, and perlite must support sufficient capillary action within the soil to keep the water flowing uphill towards the plant roots.
It might seem easier to water the containers from the top and keep extra water on hand by letting the reservoir buckets capture excess water that drips down into them. Easier, yes, but water flowing downhill through the soil as often as three times a day will carry a lot of nutrients out of the soil and away from plant roots. Not a happy thought if you want your plants to prosper.
Needless to say, how to get the soil mixture right for a container year after year is also a challenge, but that’s a topic for another note. My next note should probably tell you what’s growing in the garden, so you know what rooftop items will be appearing on the menu.