Hydroponics literally comes from words meaning “water” and “toil”. What it means now is growing plants without soil. The plant roots sit in water, which is full of nutrients. Plants don’t actually need the soil itself, but the nutrients which get absorbed with the water.
In some ways, hydroponics is simpler than traditional soil growing methods. The soil is no longer needed, which obviously makes it much cleaner and tidier than soil growing. Water losses are minimized, as it stays in the system, except what’s lost through evaporation.
Other advantages of using hydroponics in a greenhouse is tight control of nutrient levels, which can ensure ideal growing conditions as well as reducing costs. The nutrients never leave the system either, which eliminates nutrient pollution concerns. Plants grown in these tightly controlled environments will grow to higher potential, and with greater consistency. Pests are much easier to control, since they cannot hide in the soil.
If you’re growing food in your greenhouse, the substantially higher crop yields are a definitive bonus to growing with hydroponics.
Disadvantages of hydroponics are additional complexity of watering systems, and the critical nature of the overall system. If the water delivery or containment has a problem, the plants can die quite rapidly. It may also require separate containers for different plant types which could otherwise coexist in a soil environment.
There are two general categories of hydroponics, solution culture and medium culture. Solution culture uses no solids for the roots, whereas medium culture will use a solid medium for the roots such as sand or gravel.
Static solution culture is the simplest method of hydroponic growth. The plants are grown in containers of unmoving, non-aerated nutrient solution. The plants are kept slightly above the nutrient solution, so that some portion of the roots is exposed to air. This is necessary for oxygenation.
Continuous flow solution cultures, as the name suggest, involves a continuously flowing solution through the root systems of the plants. Continuous flow systems can be quite complex, although it is easier to create a fully automated system using continuous flow.
An aeroponics system will spray or the roots of the plants with atomized nutrient solution, either continuously or periodically – often enough to maintain saturation of the solution drops on the roots. This is obviously even more complex than continuous flow systems, and is probably beyond the scope of what most people would install in their own greenhouse.
Gravel medium hydroponics can use the same gravel as in aquariums, or any other kind, as long as it is washed. This method requires a continuous flow system, or the plant roots may dry out.
There are many other variations of medium and solution culture hydroponics, but these are the most likely to be examined for use in a personal greenhouse.
If you’re interested in getting started with hydroponics, the basic static solution culture method is easy to try. You can use all manner of readily available household containers, from used food containers to mason jars. Just make sure they’re washed. Determine the type of solution nutrients needed for the type of plants, and ensure it is kept at an adequate level for the plant not to dry or starve.