Once I heard that Dizengoff Center boasted an urban garden on top of the fourth floor-parking garage, I had to check it out for myself. To do so, I signed up for a workshop with LivinGreen, the organization behind the initiative. I came in with no expectations, and was pleasantly surprised to learn that the rooftop farm was about much more than just producing food.
Before I get into the nitty-gritty technical jargon of urban agriculture and the intricacies of the different aqua/hydroponic systems, I want to share the moral of the story: If Dizengoff Center can operate a successful rooftop garden, so can you!
LivinGreen advertised their goals for the “city people” of Tel Aviv as three-fold.
- To show that the average person can grow his/her own food at the most basic level. Even with simple aquaponic farming practices, you can grow the “good” stuff.
- To demonstrate that you can break-even and affordably operate as a commercial farm.
- Bring veggies from the city to the city, promoting the concept of “farm-to-table” and eating locally grown foods. In fact, LivinGreen envisions a rooftop garden every three houses! For Tel Aviv, “local” foods is defined within a 500-1000 meter radius. Compared to the United States, food is considered “local” if it is grown and consumed within a 100-mile radius!!
Dizengoff Center became a perfect pilot program because traffic congestion and pollution permeate the area, providing direct contrast to where one would suspect such an urban farm to exist. All of the food grown is in-season and chemical-free, but fun fact, is not certified organic. This is because the organic stamp of approval can only apply to food grown in the ground!! Since there is no soil or earth involved in the hydroponic and aquaponic systems, advertising as chemical-free is as good as it gets. The rooftop also hosts beehives for pollination and to encourage bees to populate the area.
Even with lights illuminating the garden at night for workshops, the whole operation runs on 200-300 volts of electricity, and has the potential to be fueled by Home Biogas. LivinGreen is using the prototype of a system that converts compost into liquid organic fertilizer and biogas. Whereas one day’s worth of a family’s waste can provide three hours of electricity, the urban garden uses the biogas to power their stove for coffee! And, to protect against the heat in Israel’s brutal summer months, shade netting covers the whole garden. Otherwise, the crops are completely exposed to the elements and nature’s wrath. Luckily for visitors, there are no mosquitos or pest problems, thanks to the lack of standing water in the hydro- and aqua-ponic systems.
So now we can get to the meat of it. The Dizengoff rooftop successfully implemented three types of hydroponics and one aquaponic system. To clarify in simpler terms, the difference between the two methods is that aquaponics applies a fish cultivation component to balance the hydroponic ecosystem. On a basic level, plants need four things to survive. If you guessed water, air, food, and sunlight (or are now nodding your head in acknowledgement), then you are well equipped to start an urban garden project!!
As a friendly warning, this is the point where those uninterested in learning the methods by which food on this rooftop garden actually grows should tune out (your welcome).
The first hydroponic on display is a closed Floating Raft system in which a floating raft made of Styrofoam sits on a table of water (pictured below). There are 2 cm radius holes for the plant bulbs, which minimizes evaporation of the system. Oxygen stones (similar to those in aquarium tanks) sit on the bottom of the relatively shallow table. Using a plant bulb or root from any corner store nursery and placing it in a plastic cone with holes, like the one featured in the picture below, place the cone in one of the Styrafoam holes.
Bottom line? A 2x2 meter hydroponic table can grow 4 times the amount of vegetables than conventional soil farming. The logic follows the fact that plants are not competing for space and nutrients. Since the roots are constantly submerged in water with a balanced concentration of food, the plants can uptake whatever, whenever they want. LivinGreen is growing kale and fennel (closer to the cash crop side), but this method of hydroponics can grow almost anything, even wheat!
Named NFT (Nutrient Film Technique), the second type of hydroponic method is the rooftop’s water pipes. As pictured, the vertically inclined pipes have holes for plant roots and for air circulation. Not pictured is the system’s water tank with a pump that sends water to the uppermost pipe. From there, gravity works its magic and keeps water flowing. As long as the roots meet the water, this hydroponic method can grow up to 8 times as much as the conventional soil cultivation methods because vertical growth makes most efficient use of the surface area. Dizengoff Center only has leafy veggies growing (because they grow fast and therefore can be sold more frequently), but vegetables ranging from tomatoes, carrots, potato, and even onions can grow! The biggest drawback is the weight; with so much room for plant growth, crops can be too heavy to sit on rooftops. However, the pipes themselves and the water tank are relatively light and still an extremely effective method of urban farming.
The third hydroponic method uses a form of gravel to anchor heavier plants such as trees. The rooftop farm currently has a papaya tree two-meters high and a growing banana tree. One notable difference here is that the water must be flushed regularly; because there is no oxygen pumped into the closed system, using the same water will cause rotting. Transforming this system into an aquaponic technique, the Dizengoff Center rooftop has a fish pool adjacent to the table in which fish waste and algae become fertilizer. This creates a biological filter with bacteria that, through nitrification, fixes ammonium into nitrites. Bioballs are plastic surface area thrown into the fish pool to create a livable environment for these bacterium. While aquaponics is a sustainable and efficient system, it is significantly harder for an individual to manage because one needs to take care of the fish. Whereas NFT and the Rafts can be checked on a weekly basis, the fish need to be monitored more consistently. For 1000 cubic liter, a successful aquaponic system such as this can sustain roughly 15 kilograms of fish and grow 5 square meters of vegetables.
Water is an essential component for all of these systems, and the ideal temperature is between 16-32 degrees Celsius. Conveniently, in Israel this ideal temperature is nearly guaranteed year-round without alteration. However, pH and Electricity Conduction (EC) of the water needs to be monitored. Because the ideal pH for plants is between 5.8-6.2 and Tel Aviv tap water is around 7, lemon is a useful and all-natural acidifier for the water. The EC of the water can easily be measured by an EC meter, which tests levels of nutrients in the water with particulates that conduct electricity. As long as temperature, pH, and EC of the water are in-check, then the plants should flourish!
From a policy standpoint, now is the time to start an urban garden in Tel Aviv… Dizengoff Center doesn’t pay property taxes. However, as policies on urban farming develop in Israel, it is expected that commercial urban farms will eventually owe property tax.
As for personal gardens, either on the roof of your own building or on your מרפסת (meerpeset- porch), LivinGreen offers a number of hydroponic systems you can bring into your own home! For example, the “Green in the House” box most closely mimics the Floating Raft system; with 5 holes for plants (bulbs placed in the cones shown above), all you need to do is add water and bottled fertilizer (provided by LivinGreen). After about a month, your crops should be green and hearty. Just dump and replace the water, and repeat! The box is small enough to fit in your kitchen, and requires the bare minimum of maintenance!
The most coveted secret of Dizengoff Center is definitely its secret garden. If you want to visit the rooftop yourself, or attend a workshop, LivinGreen offers 2-3 workshops a week. While the operation is not profitable, it serves as a valuable educational initiative for those interested in learning about urban farming and/or people who want their own rooftop gardens.