Popular Mechanics (South Africa)
PLANTS AND OPERATION
Although similar plants such as spinach and kale could probably be grown together, for best results, you should grow only one plant in a system at a time. I recommend starting with a leafy green such as rocket, which does not have a fruiting phase in which the plant makes seeds before harvest.
Before any plants go into the system, your seeds need to germinate. You’ll need to choose a growing medium. This is what the plant will take hold in, and it can be a lot of things. The industry standard is rock wool, a material very similar to glass fibre that is extremely porous and holds 16 times its weight in water. It’s the most widely used hydroponic medium in the world because it’s completely inert. There’s nothing in it, and that’s exactly what you want; you can control your variables. You can also use regular soil, a foam medium called Oasis, clay pebbles, products made from the husks of coconuts, or crumpled coffee filters in plastic plant pots. As long as you have an inert material that can hold water and oxygen, you can use it as a medium. But we’ll stick with rock wool.
Rinse the rock wool starter 1
cubes (Fig D), then soak them in water with a ph of 5,5 for about an hour. Place a seed in the hole of each starter and moisten the cubes. Keep them moist, and in a few days a sprout should appear. Put it near a window for light, and in ten to 12 days – when you see sprouts several centimetres tall and roots going to the bottom of your rockwool starters – place the cubes in their larger rock wool blocks.
The most important con2
sideration in hydroponics is consistency. If you have one, a basement is often a good place to put your system because of the even temperatures. (One easy way to tell if it’s a good place to grow plants: Ask yourself if you’re comfortable in that room. If you’re not, your plants won’t be either.) Place the growing medium in the mixing tray. Confirm that the risers for the drain fitting reach
only a quarter of the way up the medium.
Plug the water pump into 3
an electrical timer. For the majority of plants, setting your pump to run two to four times per day for 15 minutes will provide adequate water and nutrients. When the pump is on, water floods through the fill fitting and drains back into the reservoir when it reaches over the drain riser (Fig E). Once the pump shuts off, any leftover water drains back into the reservoir through the fill tube.
Hook your lights to a timer
4 and fix them above your hydroponic system in a way that light hits all parts of the grow tray. The amount of light your plant requires depends on the
plant itself and the particular stage of the grow cycle. A good reference for light timing (and nearly everything else) is Howard M Resh’s Hydroponic Food Production. For rocket, 12 hours a day will be enough for the plant to grow, but not flower.
Fill your reservoir with 60 5
litres of water and mark the water level with a pen so you don’t have to measure the next time. Having a consistent amount of water is important for correct nutrient concentration.
Look up the produce you 6
want to grow online on Cornell University’s Controlled Environment Agriculture page to find a plant-specific nutrient base. I recommend a one-part mix that can all be added at
once, like 16-4-17 hydroponic fertiliser. Follow the instructions on the nutrient mix to add an appropriate amount to the water. Change the water and nutrient solution at least every two weeks.
Keep track of the ph and 7
electrical conductivity (EC) of the water daily (Fig F). The ph should remain the same for all plants. The ideal is 5,8, but anywhere between 5,5 and 6,2 is acceptable. If your levels are off, you can adjust them with a kit bought from the pool section of a hardware store. The EC will vary based upon the plant you grow. As your plants feed, you want the EC to gradually rise. In order to lower the EC, you will add water to the reservoir. To increase the EC, add more nutrients to the system. The target EC level for rocket is 0,8 to 1,2.