What is Hydroponics? | The Basics of Hydroponic Systems

Try Hydroponics in Your Home or Apartment!

February 8, 2019
Hydroponic Lettuce (Close)
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Did you know that you can grow plants without soil? Learn the basics of hydroponic gardening—which is especially useful if you live in an apartment with access to a balcony, terrace, rooftop, or even a sunny window. Here’s an overview of hydroponics and the many types of hydroponic systems out there today.

What is Hydroponics?

The word hydroponics comes from the Greek for “working with water,” and is a method of growing plants in nutrient-rich liquid instead of soil.

This can be done outside during warm weather or indoors year-round, and has many advantages, including:

  • no weeding
  • fast growth
  • high yields in a small space
  • no critters stealing crops
  • clean vegetables
  • ease of harvest
  • consistent quality
  • no soil-related insects or diseases

One of the greatest things about hydroponics is that it can be done in a tiny space—a balcony or terrace, a small yard, the rooftop of an apartment building, and even indoors. Since it’s a self-contained system, a hydroponics setup can be scaled to any size you like (bearing in mind the weight of the water) to provide for yourself, yourself and a friend, or your family.

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Our local university has been experimenting with hydroponic growing.

Taking into account how much you want to spend, the plants you want to grow, and how high-tech you want to go, there are many options to choose from. To avoid making costly mistakes, do some research and choose the method that is right for you and your space.

Active Vs. Passive Hydroponic Systems

There are many different types of hydroponic systems, but most are considered to be either active or passive. An active system uses pumps to circulate the water, while a passive system uses gravity to move the liquid or employs a wicking material to draw water up to the roots.

Whether active or passive, most home hydroponics are closed systems that recirculate the nutrient solution through the system again and again, saving water. In an open system, the water is not captured and reused.

Media-based Systems

Although you can grow plants solely in water, for large, heavy plants like tomatoes, it helps to have some type of support for the plant roots in the form of a growing media.

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These tomato plants are growing in pea stone in an ebb-and-flow bed.

There are many types of inert growing media that can be used to hold roots in place. Common substrates include sand, gravel, polyethylene fiber, pea stone, coconut fiber, perlite, vermiculite, clay pellets, glass marbles, and rock wool.

In order to keep the growing media moist, one of the following setups is typically used:

  • A wick system, which is one of the most basic media-based methods, works like a self-watering container. Pieces of cotton or nylon rope conduct the aerated nutrient solution—via capillary action—from a reservoir sitting below the plants to the growing medium above, passively supplying moisture to the plants. This works best for plants that don’t require a lot of water, such as herbs like rosemary, thyme, and oregano, as well as quick-growing microgreens and deep-rooted plants like beets or radishes.

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Peppers grow well in an ebb-and-flow, media-based system, supported by pea stone.

  • An ebb-and-flow or flood-and-drain system can be either active or passive depending on how much work you want to do. It supplies the roots with water at regular intervals, usually several times a day, and then lets it drain away. You can do this manually by catching the water at one end of the system in a bucket after it has drained through the media and pouring it back in again at the opposite end of the system a few hours later. This type of system can easily be automated by using tubing and a submersible pump attached to a timer to move the water, turning it into an active system.

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Eggplants fed by individual emitters in a drip system.

  • Drip systems are also active. They supply a constant flow of water to each plant through a dripline. The excess water eventually seeps down to a reservoir underneath the planter and is recirculated by a pump back through the dripline again.

Liquid-based Systems

Liquid-based systems don’t use any type of growing media to support the plant roots. Instead, the plants are suspended in net pots or other holding structures with their roots exposed to a nutrient solution that has been aerated with an aquarium-type air pump.

  • The nutrient film technique (NFT) constantly supplies a thin film of aerated nutrients to the plants via a system of slanted horizontal troughs. Plants are set into holes along the top of the troughs and nutrients are pumped to the high side of each trough and flow via gravity to the low end where they are pumped through the loop again.

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Colorful red leaf lettuce thrives in the deep water raft method.

  • In deep water hydroponic systems, plants hang with their roots in a nutrient solution. For a raft-type method, Styrofoam sheets float on the surface of the water. Holes cut into the Styrofoam support the net pots and keep them from sinking into the water. The plants grow with their roots submerged in an aerated nutrient solution below the raft. This is a great method of growing lettuce, herbs, and other lightweight crops that won’t grow heavy enough to sink the raft.

Water Quality & Fertilizers

Since water is the most important element in hydroponics, have yours tested before you begin. Chemicals found in city water can be harmful to your plants and high concentrations of mineral salts can affect the fertilizer balance.

Though you can mix your own, there are both organic and chemical fertilizers made specifically for hydroponic growing systems. Some are specially designed for growing leafy crops, while others are formulated for growing flowers and fruit. Using garden fertilizers intended for use in soil won’t yield the desired plant growth and can clog up tubing and fixtures.

A slightly acidic solution (5.5-6.5) is optimal for plants to make the best use of the available nutrients, so test the pH of the solution regularly.

To prevent the nutrients from becoming too concentrated, add water to keep the level of the solution steady and change the solution regularly to keep it fresh. Bear in mind that different plants have different needs and you may have to adjust your nutrient solution accordingly.

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Basil and other herbs supported by clay pellets.

Plants for Hydroponic Systems

If you buy plants to use in your system, wash the soil from the roots to ensure that you don’t bring in any soil-borne diseases. One of the joys of hydroponic gardening is that by eliminating soil you don’t have a lot of disease problems to worry about. Good sanitation practices will help keep your system trouble-free.

Fast growth rates for many crops like lettuce, chardarugula, and other greens prevent pests from becoming established.

If you are growing your own plants from seed, you can start them in peat pellets, cubes of rockwool, or in plug trays filled with a soilless mix. Transfer them to your hydroponic system when the roots have grown through the bottom of the plug.

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Fruiting tomatoes are heavy plants and need the root support offered by clay pellets along with something to climb.

Pollination becomes an issue when growing fruit-bearing plants indoors. In an outdoor garden, tomatoes are wind pollinated. To simulate that indoors, run a fan or tap and shake the vines when they are in bloom. Look for self-pollinating varieties of cucumbers that bear all female flowers.

D-I-Y or Buy?

It’s easy to build your own basic hydroponic system using a plastic storage container as a reservoir, an air pump to aerate the nutrient solution or a submersible pump to circulate the liquid, and growing media or net pots to support the plants. For those experienced in working with PVC pipe, many space-saving configurations can be constructed to hold the plants and convey the water from one end to the other. (Lots of plans can be found online.)

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PVC lettuce tower.

If you are not that handy, the simplest thing for the beginner (even though it may be more expensive) is to purchase a kit or a ready-to-plant set-up. These can range in size from a simple drip planter to a PVC pipe garden or grow tower complete with pumps.

Unless you are growing in a greenhouse, to get the 12-14 hours of light needed daily for good growth, additional lighting will also be needed. Depending on what you are growing, this can be a basic LED growlight, which works for lettuces, greens, and herbs; or high-intensity discharge (HID) lamps for flowering and fruiting plants.

Start Small!

Start small with easy-to grow crops such as lettuce or basil and work your way up to more difficult crops as you gain confidence. Once you get your feet wet, hydroponic growing can be a rewarding alternative to traditional gardening!

If you’ve tried hydroponics in the past, share your tips in the comments below!

About This Blog

Get inspired by Robin Sweetser’s backyard gardening tips and tricks. Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer’s Market.