Hydroponics 101: A Back-to-basics Guide

Hydroponics is the practice of growing plants, food crops or flowers in a liquid medium without the use of soil. Hydroponic crops can be grown indoors year-round, regardless of the outdoor climate, so long as the needs of the crop are met. Most hydroponic set-ups are indoors, but they can also be outside.

Plants grown hydroponically need the same basic elements and nutrients as plants grown conventionally in soil: air, water, light and food.

The challenge for the hydroponic grower is to make certain plants have these requirements in the correct proportion.

Plants grown in soil are able to get many of the nutrients they need from their environment, as healthy soils contain some combination of the macro- and micronutrients plants need to survive.

Soil also provides a structure for the plant to develop and be supported in. A hydroponic grower must account for these imbalances and take the necessary steps to remedy them.

An advanced degree or engineering experience is not required to assemble and successfully maintain a hydroponic system.

It can be as simple or as elaborate as one wants. Constructing and tending to a hydroponic system can be a great family activity or an educational experience for students of all ages.

Growing plants hydroponically can introduce a person to concepts as diverse as sustainable agriculture, plant life cycles, basic chemistry, engineering, irrigation and the spectrum of light energy.

Hydroponic System Must-haves

Regardless of the type of hydroponic system chosen, there are a few must-haves. Clean, fresh water with a pH conducive to plant growth is the foundation of hydroponic growing.

Different plant crops have different pH requirements, but most plants suitable for hydroponic growing prefer a pH in the range of 6 to 6.5. Testing the pH of your water is easy.

Do-it-yourself kits can be obtained in most hardware stores, garden centers and hydroponic stores. If you are unsure of how to test, for a nominal fee you can collect a sample and have it lab tested by hundreds of labs across the country and maybe even your county or municipal water department.

If your pH is unsuitable, you will need to amend the water with formulations that either raise or lower the pH, which can be found in all hydroponic supply stores.

Air flow is important not only in the environment around the plants, but in the water, too. The water must be continually oxygenated and cannot be allowed to become stagnant.

The placement of a fan and the addition of a pump, like those used for fish tank aeration, are suitable and relatively inexpensive.

The air flow around the plants helps reduce incidences of disease by helping dry the foliage. Moist foliage can be a breeding ground for many fungal diseases.

If your hydroponic site is inside, or set up in an area without ample natural light, supplemental grow lights are needed.

There are many different types of lights manufactured specifically for growing plants. The type of light chosen should be appropriate for the crops you wish to grow. Make sure you choose lights that offer light across the visible spectrum.

All plants require lighting in the blue end of the spectrum during their vegetative stage and crops harvested before flowering such as lettuce, kale and spinach do best using only this type of light.

Fruiting or flowering plants need light in the red end of the spectrum during the bloom stage of development.

A standard incandescent light is not sufficient for growing plants, as it does not offer light across these spectrums.

Either a combination of lights is required, or one type that offers light at both ends of the spectrum. Duration of light is another consideration—lettuce plants do not require as much light as plants like tomatoes or peppers.

A timer can be placed on the lights and adjusted as necessary, depending on the amount of natural light received and the type of crop grown.

As for growing mediums, several different options are suitable. While hydroponic growing does not use soil, some sort of medium is required to give the plant some structure to grow with.

The ideal medium should be lightweight, porous and able to retain moisture and nutrients well. Mined or harvested materials such as porous pebbles, perlite and rockwool work best.

Rockwool is a spun rock material that can raise your pH, so it should be conditioned before use.

Natural materials like coco coir (coconut fiber) and sphagnum moss (not peat moss) are also excellent for hydroponic growing.

Materials like sand and gravel can be used, but are heavy and have other drawbacks. Sand can compact too much, not allowing for proper aeration, and gravel does not retain water, so if there was a system failure, the plants would dry out.

How to Set Up a Basic Hydroponics System

Site selection is key. Make sure you set up your system in an area with access to power. Access to water is needed, too.

Do not put your system in an area that would be damaged or otherwise compromised if it were to get wet, as leaks or system failures sometimes happen.

The simplest systems to set up are those where the reservoir and the growing area are one and the same.

These can be made out of a fish tank, terrarium or any other vessel that can hold water and is large enough for a pump of some kind. In these set-ups, the plants float on top of the water, which the pump keeps constantly moving.

A piece of polystyrene or other lightweight floating material that will not dissolve or affect the pH is cut to size to fit on top, and holes are cut into this material to accommodate the media or mesh pots containing the media.

It is relatively easy to expand on a basic system. Additional tanks can be added as well as sections of gutter or pipe.

These can be filled with clay pellets or pots filled with your choice of media. The main thing to account for when enlarging a system is to make sure the pump is powerful enough to move the additional water.

Any supplemental lighting should be placed as close to the plants as possible. The effectiveness of light is reduced exponentially the further away it is from the plant. Lights should be set up so they can be moved up as the plants grow.

Seeds can be sown directly into the media as long as they are not prone to being dislodged by the movement of the water.

Otherwise, plants can be started in a soilless media and then transplanted into your hydroponic system once they have matured beyond the cotyledon phase and plants have developed their first set of true leaves.

How Do I Monitor a Hydroponic System?

You must check your hydroponic crops regularly. At least weekly (unless your plants are showing signs of stress, in which case as needed), check the water to see if the pH and nutrient levels are where they should be.

Check the plants for signs of pests or disease. Monitoring cards are sticky yellow or blue cards that attract flying pests and can be placed near your crops. Checking these and replacing them regularly is an excellent non-chemical tool in insect scouting.

The mechanics of your system should be checked regularly as well. Make sure the pump is not clogged, and if there is a filter, clean or replace it regularly. Check the lights and the timer as well to ensure proper operation.

There is much disagreement on the frequency of water replacement in a hydroponic system. The water should be changed on first indication of any disease so the pathogens are not freely circulating.

The water should also be changed between crops to make sure there are no lingering pieces of decaying leaves or roots from previous crops.

In general, it should be changed and the reservoir cleaned anytime you notice it is dirty or if the plants are not performing well.

Be mindful of any nutrients that may be in the water, and do not dump it anywhere it is likely to end up in waterways.

A compost pile is the perfect receptacle for used up hydroponic water, or it can be diluted and used to water your lawn or landscape.

Follow these instructions and you’ll be well on your way to growing hydroponically.