What is Hydroponic Gardening?

Hydroponic gardening is a popular soil-free gardening method that has become increasingly popular and accessible over time. Home gardeners and commercial producers alike can grow healthy crops, save money, and even learn a bit about the science behind gardening through this method. These water-based systems can be huge comprehensive setups. They can also be simple, compact, and controlled with the flip of a switch.

Yet, for a beginner, it can be hard to understand all of the materials and techniques that are needed for this process Let’s break them down so that you feel confident when deciding to start an indoor hydroponic garden.

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two people transplanting a hydroponic lettuce plant.

A Basic Definition

Hydroponic Gardening is the art and science of growing plants without soil. This is achieved by growing plants in a water-based, nutrient-rich solution. The plant is supported by a material referred to as an inert medium, or media.  Gravel, sand, peat, vermiculite, pubice or sawdust, will hold plants in place in the hydroponic system. These mediums also allow nutrients and oxygen to reach the plant.

Benefits & Downsides of Hydroponic Gardening

The main advantage of a hydroponic garden is its efficiency. Plants can grow up to 25% to 50% faster and can produce up to 30% more material than their soil-based equivalents. It’s believed that extra oxygen in the growing medium helps support and stimulate root growth, leading to healthier plants.

Hydroponic systems make it easier for a plant to find nutrients. In soil, a plant needs to search for and break down nutrients. In a hydroponic system, nutrients are directly delivered to the roots in a water-based solution. This allows plants to conserve their energy for the much more important task of growing large, blooming, and fruiting.

Large scale hydroponic systems may play a role in environmentally sustainable gardening and farming.

A surprisingly small amount of nutrients and water are needed in this closed system, and they are used very efficiently since they are recycled through the plants over and over again. Soil-based gardens may have their nutrients washed away and provide less effective nutrient delivery overall.

Additionally, less pesticide is needed because hydroponic systems tend to be less prone to microbial or insect infestations.

Hydroponic gardening has been a major solution for the micro farmer, urban gardener, and indoor gardener.

Small scale hydroponic systems come in a variety of methods and sizes for those with less available space and sunlight.

The main downside of the hydroponic system is its price, depending on the type of system you would like to invest in. Even though the system may pay for itself down the line, it will almost always be more expensive than it’s soil counterpart.

Another disadvantage is the time that hydroponics takes.  The system itself will take time and careful attention to set up properly. You will also have to dedicate time to learning about the materials and methods you will be using.

While plants are generally safe in hydroponic systems, if there is ever a failure with your setup, there is a risk that your plants may die. This is because the roots will not be able to find water stored in the soil like it normally would when it has been planted.

The History of Hydroponics

Painting of Aztec Floating Gardens
Market in Tlatelolco, Diego Rivera

Hydroponic gardening is an ancient technology. Its first documented use was in the Hanging Gardens of Babylon around 600 B.C. The Babylonians may have used a pulley system to draw water from the Euphrates River to deliver it to the plant roots.

Similarly, floating gardens were found in the 10th and 11th century in the ancient city of Tenochtitlan. This ingenious farming technology allowed the Aztecs to convert their marshy wetlands into a viable agricultural area. This process was so efficient that the gardens yielded crops up to 7 times each year.

Hanging gardens were also used in China in the 13th century, and the cultivation of rice fields is also sourced as an early form of hydroponic culture.

In the 1804, Nicolas De Saussure published an investigation demonstrating that plants are composed entirely out of mineral elements obtained by water, soil, and air. This idea lead to the identification of essential minerals needed in plant development. Several scientists of the 19th century experimented with them in water solutions.

In 1860, Professor Julius von Sachs published the first standard formula for a nutrient solution that could be dissolved in water from which plants could be successfully grown.

In the early 20th century, Dr. William F. Gericke of the University of California termed these nutriculture systems “hydroponics”. Two Greek words make up this name. Hydro, meaning water, and ponos, meaning labor, form into the contemporary term hydroponic.

Hydroponic technology made its way into contemporary agriculture as a major solution to greenhouse gardening. This has naturally extended into an indoor gardening solution as well.

Over time, a diversity of methods and techniques have developed, making this once specialized approach doable for all levels of gardeners.

Growing Mediums (Media)

closeup photo of expanded clay pellets.
Expanded Clay Pellets

Without soil present, your plants will need a material that can hold them up, as well as transport moisture, oxygen, and nutrients to the plants’ root system. This is called a growing medium.

Growing medium does not provide nutrients to the plant itself. A good growing medium is light, loosely packed, and drains well. It won’t break down or decay easily, providing the best conditions possible for the plant. 

There are several types of growing media available for hydroponic gardening. Here is an introduction to some of the most popular ones:

  • Rockwool: Rockwool is a sterile and porous non-degradable material that is made out of limestone and granite. It is a very popular choice for both hobbyists as well as commercial farmers. It holds water very well, has great oxygen retention, and comes in a variety of sizes and shapes. Like any material, it has drawbacks as well. It is not pH neutral, creates dust particles, and can be nearly impossible to dispose of in an environmentally friendly way.
  • Perlite: Perlite is composed of several minerals that are exposed to high heat, which expands them into lightweight, porous, and absorbent materials. Perlite can be used on its own or mixed into other growing media. It’s naturally steril, which can help protect plants from rot and disease. Unfortunately, it may be too lightweight for certain hydroponic systems, and it may produce dust.
  • Expanded Clay Pellets: These are small circular balls of clay that are heated into durable pellets. They are also referred to grow rocks. They are sturdy and gentle with plants, and have a neutral pH. However, as they age, the clay can break down, which can clog your system’s pumps and emitters.
  • Vermiculite: Like Perlite, this material is made by expanding minerals under extreme heat. This substance has a great moisture and nutrient retention capacity. However, it is possible that it may hold too much water, and is an expensive choice.
  • Coconut Coir: This organic material is made out of coconut shell husks and fibers. This material holds water and oxygen well, is organic, and is a renewable material, making it environmentally friendly. Unfortunately, it does not have great drainage, so is often best mixed with another media.
  • Starter Plugs: These are made from natural materials such as peat moss. They’re used for seed germination and rooting cuttings. They can help grow strong stable plants, but are also quite expensive, and only used for seedlings or cloning.
  • Pine Shavings: This is an inexpensive growing media that is popular with commercial growers using large scale hydroponic drip irrigation systems. You can find pine shavings in pet supply stores, as it is used as animal bedding. They can hold a large amount of water, and can become waterlogged fairly easily, so it may be best to add a large rock under the shavings to aid in drainage.

Nutrients

Many of the principles that apply to soil fertilizers are also the same in hydroponic gardening. Nutrients can be purchased pre-mixed in liquid or powder forms. Liquid fertilizer is a bit more expensive but provides better nutrient availability to the plant. Powdered fertilizer is more affordable but is harder to dissolve into water and may be less bioavailable.

Additional considerations such as solution strength, organic or chemical grade fertilizer, and nutrient balance can all contribute to the health of your hydroponic plant.

Plants need macronutrients and micronutrients. Macronutrients are needed in large amounts, and consist of Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and Sulfur (S). The following micronutrients are required in smaller amounts but are still necessary for the health of the plant. These are Zinc (Zn), Manganese (Mn), Iron (Fe), and Boron (Bo).

Here is an overview of the main nutrients used in hydroponics, as well as a few tips for spotting a nutrient deficiency:

  • Nitrogen (N) is the primary food for plant growth, particularly in the vegetative growth phase. Your plants will need Nitrogen if they are short and the older leaves are displaying a pale yellowish-green color.
  • Phosphorus (P) is necessary for photosynthesis and seed production. Plants need phosphorus in large quantities in their early seedling, germination, and flowering stages. Your plant may need phosphorus if it is not reaching maturity and is stunted. It is also difficult for a plant to absorb phosphorus if the environment is too cold.
  • Potassium (K) is vital for all stages of a plant’s growth. It helps the plant synthesize carbohydrates and also supports the development of roots, stems, and flowers. It can also support resistance to bacteria and insects. Your plant may need more phosphorus if you notice older yellow leaves with scattered brown and black dots on them.
  • Calcium (Ca) is particularly important for fast-growing flowers and vegetables. Calcium deficiency affects young leaves, distorting them, and creating dead spots on them. It also inhibits bud growth in the flowering phase.
  • Magnesium (Mg) aids in chlorophyll production and supports the photosynthesis process. This deficiency occurs frequently with tomato plants. The older leaves will yellow, however, the veins will remain green.
  • Sulfur (S) supports the production of the 21 amino acids that create proteins, as well as the hormone production of a plant. It is rare that this mineral is deficient, and can occur as a yellowing of new leaf growth.
  • Iron (Fe) is important for a plant’s enzyme and chlorophyll synthesis systems. Much like a magnesium deficiency, it can be spotted by its production of yellow leaves with distinct green veins. It is also hard for the plant to take up Iron in cold climates.
  • Manganese (Mn) supports the work of iron in producing chlorophyll. A plant lacking manganese may develop brown dry yellowing leaves.
  • Boron (Bo) supports the formation of cell membranes and chlorophyll production. Plants with a boron deficiency may grow smaller, denser, and leaf edges may pucker and show yellow spotting.
  • Zinc (Zn) aids in stem growth and is a catalyst for enzyme production. Plants needing additional zinc may grow smaller and show large amounts of pickering and shape distortion.

pH

a person holding pH test strips.
pH test strips

pH lets us know the acidity or alkalinity of a solution, based on a scale from 0 (acidic) to 14 (alkaline). A ph is neutral at 7, and pure water has a pH of 7.

pH affects the absorption and availability of the minerals and nutrients that a plant needs. When the pH is in the wrong range, a plant can reach toxic levels. Most plants will grow hydroponically within a pH range of 5.8 to 6.8. A pH of 6.3 is considered ideal.

It’s easier to check the pH in water than it is in soil. You can get a pH testing kit online or at a local hardware store. This is an important aspect of hydroponic gardening and the pH should be checked once a week. You can easily adjust the pH by adding a small amount of soluble Potash to raise the pH, and phosphoric acid will lower the pH.

It can be helpful to take notes when you are learning how to balance the pH of your hydroponic system. You can track how much pH modifier, water, and nutrients are needed to hit the sweet spot close to a reading of 6.3.

When there is an extreme change in the pH of your system, this may indicate it is time to do a nutrient change. It may also be a sign that you are using hard water, which means that your tap has a high alkalinity. Some options to create a more neutral pH from your tap water are to filter the water you put into your system, or to install a reverse osmosis system  onto your sink in a more extreme case.

Grow Lights

If you’re able to place your hydroponic system in front of a super sunny window in your home, that’s great!

However, not all of us have spaces that allow for optimal sunlight, such as a south-facing window in the northern hemisphere. Furthermore, indoor sunlight can be inconsistent depending on weather and seasons.

Enter the grow light! Technology has improved significantly over the years. Here  are three main categories of lights for you to consider:

  • Incandescent Grow Bulbs: At $20, these lights are very affordable, but do not provide the full spectrum of sunlight. Because of this, your herbs wont grow to their full size, flavor, and nutrient potential.
  • Fluorescent Grow Lights: For $30, these lights can provide a good hanging setup that can provide more even light for your herbs. However, it still won’t provide the benefits of a “full spectrum” of light unless you purchase a more expensive setup.
  • Full Spectrum LEDs: With an investment beginning at $150, this light provides a full spectrum of light that will bring the best out of your herbs. They are also highly energy-efficient and their average lifespan can last for over 50,000 hours.

Make sure to mind the temperature of the lights that you choose, which could potentially harm the plants. Good circulation can help improve temperature conditions in this case.

Systems

Ebb and Flow Systems

Ebb and flow systems need a media, such as perlite, to secure the roots themselves. There is no nutritional value from this medium. In this system, there is a tray in which the plant is placed in the medium. Below the tray is a separate container containing water, nutrients, and minerals.

Water is periodically pumped into the tray, which floods it and gives the plants a chance to absorb the nutrients. Gravity eventually pulls the water back down into the reservoir. This type of system works best with small plants such as herbs and is a great option for an at-home hydroponic setup.

Nutrient Film Technique (NFT)

This system is similar to the ebb and flo system because it uses a pump to send nutrients and water into the grow tray. However, in this method, the nutrients are constantly flowing over the roots.

The growing tray is placed at an angle that allows the water to flow towards the drainpipe, recycle itself, and wash back up over the roots. Only a small amount of the nutrient solution runs over the roots to make sure they are not completely soaked. Using just a thin “film” of water also allows for more oxygen availability to the roots.

This technique works best for lightweight and fast-growing plants. The roots are not suspended in a growing medium with this method. Top-heavy plants will need additional supports to thrive in an NFT system.

Drip Systems

This system is also called a trickle or micro-irrigation system. Drip systems have a very similar setup to the ebb and flow system. It has tubes, pumps, and growing medium.

However, in a drip system, several small tubes pump and drain a nutrient solution on top of the plants. This method is best for plants with underdeveloped root systems. It’s also a great method for smaller plants.

Aeroponics

This method does not require a medium for the plant. Trays suspend the plant which allows for the roots to dangle below. Then the tray is put into a container with a small amount of water and nutrients at the bottom. This solution is carried up by a pump and misted over the root system. This continuous stream of mist can provide as much nutrient availability as a stream of water.

These systems can be tricky to set up but have great benefits as well. There are also commercially preassembled aeroponic machines for purchase. Plants use less water overall, oxygen is more available for the roots, and may help the plant grow faster. 

Wick Systems

This is another medium based system and it is also one of the simplest methods for a hydroponic setup. There are no moving parts in this system, so it is considered a “passive” system. This can make it much more affordable and easier to troubleshoot.

The wick system uses two or more wicks to bring water from the lower container up to the roots. A nylon rope is placed at the base of each root and it is placed over the container to create a connection with the water and nutrients below. The wick now brings the water up into the root system.

This method is best for lettuce and herbs. It isn’t a great method with “thirsty” plants such as tomatoes because the water and nutrients may not be delivered fast enough in this system.

What can you grow in a hydroponic garden?

Clippings of 6 different plants

Now to the fun part – choosing which plants you will grow in your hydroponic system! You can grow most plants in a hydroponic system if you are diligent and provide the correct nutrients and a proper setup.

Steer clear of plants with deep root systems such as turnips, potatoes, and carrots. Plants that require large amounts of space are also tricky to grow, so avoid pumpkins, squash, and melons as well.

Here is a list of 12 great plants for beginners starting a hydroponic garden:

  • Lettuce
  • Spinach
  • Tomatoes
  • Strawberries
  • Peppermint
  • Tarragon
  • Peppermint
  • Basil
  • Lemon Balm
  • Rosemary
  • Oregano
  • Sage

What is your budget?

It’s important to know how much money and time you want to invest in your hydroponic garden before you choose the method, system, and plants that you will use. The cost of your system can range from $50 for a simple arrangement to $2000 for an indoor farming installation.

You can choose to build your own system or purchase a pre-made system, which allows you to choose how much you want to invest in the system.

There will be both initial setup expenses and continuous expenses when setting up your hydroponic system.

Add up the cost of your hydroponic system, growing medium, seeds, plants, nutrients, pH strips, and any other accessories you may want for your garden. These are your startup expenses.

For recurring expenses, you’ll mainly have to consider the cost of your lights. There is the bulb itself, which will last different lengths of time depending on its quality. Additionally, the efficiency of the bulbs will determine how much your electricity bill will increase.

You will also want to consider the amount of value your hydroponic system can bring you. If you maintain your system well and use excellent materials, your plants will likely have large yields. Over time this can save you a significant amount of money.

To predict your yields, you can research each plant you are going to grow and set goals for yourself. This also helps you identify whether your plants are under-producing.

Where will you put your hydroponic garden?

For an indoor hydroponic garden, make sure it’s in a location where children or animals can’t reach it.

It will also need to be in an area where there is good air circulation or a spot where you can easily place a fan near your system.

Although often not mentioned, it is very important to put your hydroponic garden in an area that brings you joy. You may want it in your kitchen so it is nearby for easy culinary herb pruning. It may look great in your at-home office where it can bring a punch of freshness to the room.

Ultimately, placing your hydroponic garden in an area that feels good will encourage you to give it attention and quality care.

Additional Resources

  • Home Hydroponics: A short PDF class by Ruth Sorenson and Diane Relf at Virginia Cooperative Extension.
  • Hobby Hydroponics by Howard M. Resh. CRC Press, 2013/2017. A brief contemporary guide with several helpful images.
  • How to Hydroponics by Keith Roberto. Futuregarden, Inc., 2003. A full-coverage guide that introduces hydroponics and explains how to create your own hydroponic system
  • Commercial Hydroponics by John Mason. Simon & Schuster Australia, 2000. A guide to hydroponics on a larger scale.

There you have it, by now you should have a basic understanding of each part of the hydroponic gardening process. Remember that with research, application, and practice you will pass the learning curve.  Then you can move on to enjoying the plants in your home and on your plate!

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