Hydroponics 101

Credit: Terry Guscott

This could well be the fastest-growing gardening trend – despite the bad rap. The gardening method of choice amongst the flourishing illegal marijuana industry in B.C., hydroponic techniques have in fact made a substantial contribution to the province’s legitimate agricultural industry, and are now finding increasing favour with home gardeners, too.

Hydroponics (from the Greek “water working”) is a gardening method that dates back to as early as the Hanging Gardens of Babylon. It’s simply a means of growing plants without soil.

Soil-less gardening offers many advantages to the home gardener. Since a sterile medium is used, there are no weeds to remove, and soil-borne pests and diseases are minimized, if not eliminated completely. Hydroponic gardens use less space, since the roots do not have to spread out in search of food and water. The biggest advantage is the ability to automate the entire system with a timer. Automation reduces the actual time it takes to maintain plant growth requirements and provides flexibility to the gardener who can be gone for long periods of time without having to worry about watering. Among the most popular edibles being grown hydroponically by home gardeners are lettuce, tomatoes, peppers, cucumber, basil, cilantro and chives – ensuring that there is always a fresh salad within arm’s reach.

Justin Cooper, co-owner of Pacific Northwest Garden Supply in Surrey, says this method of gardening is also good for the environment. “Hydroculture doesn’t require the use of pesticides or weed killers. The nutrients are recirculated, so there’s less pollution. Some systems don’t even use electricity.”

Testimony of the efficiency of the system is as near as your local produce market – BC Hothouse fruits and vegetables are grown this way. “The method is especially good for growing tomatoes and cucumbers, a huge part of the commercial industry,” says Daryl Markiewicz, a sales rep with Solar Greenhouse and Hydroponic Supply in Burnaby. “It shouldn’t be confused with organic methods,” he cautions. “There is simply a change in the use of technology from conventional growing methods; it is not necessarily an organic method, although it can be.”

Hydroponics can also be called controlled environmental agriculture. In a completely controlled system, you can adjust light, temperature, water, carbon dioxide, oxygen, pH and nutrients in order to obtain the desired result.

“That’s one of the reasons orchid growers like hydroponics so much,” says Markiewicz. “You can replicate the plant’s natural environment even if you live in a windowless high-rise apartment.”

According to Rick Phillips, vice president of sales and marketing for General Hydroponics in Sebastopol, California, the hydroponic growing method is very popular in the Third World where arable land and ample water are in short supply. “It’s estimated that in 50 years there will be a worldwide water shortage, so hydroponics will become even more popular because the plants don’t need constant irrigation,” he says.

Markiewicz is quick to point out another advantage to hydroponic gardening methods: “If you can’t bend down to work in a backyard garden or if you’re in a wheelchair, you can set the garden up to meet your needs, as well as the plants’ [needs]. Seniors and disabled individuals like it for those reasons, and because it’s much cleaner than regular gardening.”

The system itself can be as simple or as complicated as you want it to be. For example, placing a cutting in a glass of water and setting it on a windowsill is a very crude form of hydroponic gardening since no soil is involved in the process.

In soil, biological decomposition breaks down organic matter into the basic nutrient salts that plants feed on. Water dissolves these salts and allows uptake by the roots. For a plant to receive a well-balanced diet, everything in the soil must be in perfect balance. Rarely, if ever, can you find such ideal conditions in soil due to contamination and biological imbalances.

With hydroponics, water is enriched with these very same nutrient salts, creating a nutrient solution that is perfectly balanced. And since this solution is contained, it does not harm our environment the way that runoff from fertilized soil can.

Here are the basics of most hydroponic systems:

Growing Medium
To support the plants in a hydroponic system, an inert soil-free medium may be used to anchor the roots. Such a medium is designed to be very porous, allowing for the excellent retention of air and water needed for a healthy plant. The most popular growing media are “heydite,” small pieces of shale rock that can be reused indefinitely, and “rockwool,” a product made of rock that has been melted, spun like cotton candy and moulded into growing blocks and slabs. Sometimes bark is used as a medium for growing orchids.

Nutrient/Plant Food
This is arguably the most important factor in the success or failure of a hydroponic system. In addition to a perfectly balanced diet, hydroponic plants have their food and water delivered directly to their roots. This way, the energy normally used to develop long roots can be redirected to growing more plant. Food is supplied by dissolving natural fertilizer “salts” in water to make a nutrient solution. It is important to feed the plants the proper amount of each nutrient (this varies with the type of plant grown). Because you are growing in a soil-less medium you must provide all the nutrients the plant requires. There is no other source of nutrition available to the plant as there would be if you were growing in soil. It is necessary to use a fertilizer formulated for hydroponic growing that will provide both micro and macro nutrients in the right balance for optimum plant health.

Oxygen
Without ample oxygen to the roots, the plant will drown. In addition, air circulation around the leaves mixes the air, allowing the plant to draw out the carbon dioxide necessary to carry on photosynthesis. Air circulation also helps prevent fungal diseases caused by moist, stagnant conditions. Indoor units often have a small fan to help circulate the surrounding air.

pH (Potential Hydrogen)
The pH level refers to the “acid” or “alkaline” level of the nutrient solution. The scale ranges from 0 to 14, with anything below 7 considered “acidic.” Most plants prefer a pH level between 5.5 and 6.5. A pH level that is too high or too low can affect the plant’s ability to use the nutrients.

Light
With proper exposure to natural sunlight or supplemental grow lights, hydroponic plants will grow many times faster, bigger and healthier than those grown in soil. Metal halide lamps, sodium vapour lamps, gro-lights or fluorescents used in conjunction with incandescent bulbs will provide adequate light.

Hydroponic Systems
Hydroponic systems come in many sizes, shapes and degrees of complexity, including the nutrient film technique, aeroponics, the aeration method and aggregate systems.

The nutrient film technique uses a plastic trough or tube as the container through which a constant thin film of nutrient solution flows. Plants are suspended through holes in the top of the trough, which is gentle sloped to flow the solution back to the nutrient reservoir. The many variations of this system make it the most popular for the home gardener.

Aeroponics entails growing plants in a container in which the roots are suspended in a nutrient mist rather than in a solution. The most popular container for aeroponics is an enclosed A-frame constructed of Styrofoam boards. Plant roots are suspended mid-air inside the chamber, which is kept at a 100-per-cent humidity level and fed with a fine spray of nutrient solution. This mid-air feeding allows the roots to absorb much-needed oxygen, thereby increasing the metabolism and rate of growth reportedly up to 10 times of that in soil. And there is nearly no water loss due to evaporation.

One of the first systems to be developed, the aeration method uses an aquarium air pump to bubble oxygen to the roots of plants immersed in the nutrient solution. Plants are suspended above the solution by a five-centimetre-deep mesh tray that is set into the container by placing the lip of the tray over the container’s edge. A layer of inert material, such as vermiculite, is placed in the tray to provide stability for the plants, while allowing the roots to grow down into the nutrient solution.

Aggregate systems use some form of inert material to support and surround plant roots. The most common materials are rockwool, clay pebbles, gravel, perlite, vermiculite, sand or foam chips. The medium provides plant support, allows good oxygen penetration to the roots, and yet retains a thin layer of nutrients and water around the roots. One of the most common systems using an aggregate medium is the flood and drain method. In this instance, a container is filled with the aggregate and plants. The container is flooded periodically with the nutrient solution, which is drained back into the nutrient reservoir by opening a valve at the bottom of the container.

Another common aggregate system is the trickle feed method. In this case, the nutrient solution is continuously pumped from the reservoir through a 1/2-inch irrigation tube that branches into a number of 1/8-inch tubes. These smaller tubes deliver the solution to the containers. Any excess is collected at the base of each container and returned to the reservoir. A modification of this method is called tube culture. A 10- to 15-centimetre plastic tube or bag is filled with a lightweight aggregate. Holes are made on all sides of the container for the plants. The tube is hung vertically and an irrigation tube is positioned at the top of the container. The nutrient solution seeps through the container and may or may not be recycled when it reaches the bottom.

Even the most sophisticated system is not entirely foolproof. “The most common mistake is over-fertilization,” says Markiewicz. “People often assume that more is better, but when the plant reaches its nutrient saturation point, it stops growing. The good news is, compared to having this type of problem in a conventional garden, the problem is easy to fix. You can just change the water and start over. You can’t do that if you’re growing in soil.”

Not every plant is suitable for growing hydroponically, either. “Carrots, radishes and that sort of thing don’t work very well,” says Cooper. “Basically, anything that grows above ground works okay. Even so, some systems work better for certain types of plants. Windowsill systems [many come as kits] are the perfect size for growing herbs. Orchids don’t like having wet feet, so growing in bark mulch might be a better solution than suspending them in water.”

So think about what you want to grow and where you want to grow it before setting out to buy your hydroponic system.

A freelance writer and avid organic gardener based in Sechelt, Janet Collins is also an established weaver and needle-felter.