Hydroponic growing means using a nutrient solution to feed plant roots without soil. Hydroponic growing systems can be simple and small enough to be placed in the kitchen for growing culinary herbs. Large greenhouses can use hydroponic methods to produce food crops and commercial quantities of out-of-season plants. The learning curve to be proficient in hydroponic growing is steep and large systems are costly.

Types of Hydroponic Growing Systems

All hydroponic growing systems have several components in common, but differ in how the nutrient solution is provided to the plants. Systems have a tray on which plants are placed either directly or in containers and they have a reservoir of nutrient solution that feeds the plant’s roots. Most hydroponic growing is done indoors and is supported with grow lights, a growing medium that supports the plants, and controls for ambient temperature.

Hydroponic systems may be active or passive depending on how nutrients are made available to the plants. In passive systems, a nutrient solution is always present for the plant roots and there are no moving parts. Small kitchen herb gardens are often passive hydroponic systems that use wicks made of cotton or nylon to suck nutrient solution from the reservoir to the plant roots through capillary action.

Active systems require a pump and a pump timer to send nutrient solution to the plants. Three common active hydroponic systems are drip, flood and drain, and nutrient film technique. The flood and drain hydroponic system—also called ebb and flow system—pumps the nutrient solution through a tube into the plant tray. Drip hydroponic systems also pump the nutrient solution. However rather than flooding the plant tray, these systems push the solution into a drip manifold that drops a small amount of solution onto the plants.

The nutrient film technique (NFT) for hydroponic growing feeds the nutrient solution into a sloped tube or gutter that has holes cut for the plant to grow upward and the roots to drop into the gutter as the solution flows past. The active hydroponic systems pass the excess nutrient solution back into the nutrient reservoir through a drain tube.

Pros and Cons of Hydroponic Growing Systems
All hydroponic growing systems require the gardener to provide supplemental light for plants from fluorescent or special purpose grow lights. Temperatures where plants are growing hydroponically must be within the correct range for the plants which may be cooler or warmer than the desired temperatures of those living with them. Growers must also routinely check nutrient levels in the reservoir and pH of the solution.

Passive hydroponic growing systems are the easiest to build and the least costly. They work well for small plants like herbs, but do not provide enough liquid for larger plants. Active systems rely on pumps to move the nutrient solution to the plants. Therefore, these systems are compromised if there is a mechanical failure of the pump or a power outage. Tubes and drains in active systems can easily become clogged which can lead to too much water remaining on the plant’s roots or no water coming through clogged drip manifolds.

Active systems are more expensive than passive systems and are usually placed in a greenhouse. The initial capitalization of commercial or large hydroponic growing systems is several thousand dollars which can daunt a hobbyist.

Another constraint for some people in using active systems is the need to set pump timers and actively monitor a range of growing conditions including venting the greenhouse, heating in cold weather, and maintaining enough, but not too much, humidity.

Successful hydroponic herb and vegetable growing is possible and rewarding. Beginners should start small and learn the basics before moving into more complex hydroponic systems. Over time, a grower will appreciate how productive a hydroponic growing system can be and will value the availability of out-of-season vegetables and plants.