Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
Hydroponics is a NASA-developed system for growing plants using only water, light, fertilizers, and various inert growing mediums.
Hundreds of plants can be grown in a hydroponic system, though some of them, such as carrots and trees, are impractical.
NASA has managed to grow potatoes hydroponically, but generally, root plants are better grown in soil. Leafy vegetables and nightshade plants are the most popular.
What Can You Grow with Hydroponics?
Most plants need light, water, oxygenated roots, 17 nutritional elements, vertical stability, supporting temperatures and humidity, and carbon dioxide to live.
In addition to these factors, taproot vegetables like carrots, turnips, and parsnips need a growth medium that offers some resistance to develop optimally.
If you exclude these difficult-to-grow plants, you still have many vegetables, fruits, flowers, and herbs that can grow in a hydroponic garden.
Below is a table with a non-exhaustive list of possibilities of vegetables, herbs, and fruit that carries some of the best plants for hydroponics.
Whether grown indoors or outdoors, hydroponic systems allow you to grow plants that develop uniformly.
There are a variety of hydroponic systems, including ones that require minimal investment and are suitable for home gardeners.
There are also more advanced systems, but unless you want to sell products, these systems are hard to justify financially.
Popular home crops that do well in polytunnels are:
The Brassica family (kale, Brussel Sprouts, mustards)
The Solanaceae family (tomatoes, peppers, eggplants)
Leafy greens (lettuce, spinach, Swiss chard, endive)
Climate permitting, an outdoor hydroponic system allows you to grow almost anything.
If it can be grown in a pot or container, you can grow it in a hydroponic garden.
Which Hydroponic System is Best for Home Gardeners?
There are two categories of hydroponic systems: liquid and aggregate.
Plant roots float freely in a liquid system unsupported by a growing medium.
In an aggregate system, the roots grow in an inert medium through which water moves freely.
Aggregate systems may use active or passive water-supply systems.
Hydroponic systems are divided into open and closed systems referring to nutrient usage.
Open systems use nutrition-laden water once, while closed systems continuously recycle the water and replenish nutrients as needed.
As mentioned earlier, aggregate systems use passive and active methods for water delivery.
The passive approach doesn’t require pumps that create a water flow over the plant roots but instead uses a high capillary action wick to transport the water to the roots.
Types of Hydroponic Gardening Systems
Below is a review of the six most common hydroponic garden systems.
I expand on hydroponic systems you can affordably use at home.
Deep Water Culture (Home-use Winner)
Also known as the floating platform or water culture system, it has a polystyrene platform that allows the plant roots to remain partially submerged in nutrient-enriched water.
An air pump continuously forces air for water aeration.
This is the most straightforward hydroponic system at home and can often be bought as a kit. All you need to make your own is a deep-bottomed container, an air pump, and an air stone (and connecting pipes).
Each plant is placed in a perforated cup or a unique basket (net cups) that fits into round slots cut into the polystyrene board, allowing part of the plant’s roots to dangle in the water.
I prefer using coconut coir as an anchorage for the plant in the net cup, but perlite, clay pellets (Hydroton®), pumice, or Rockwool, are all popular alternatives.
NASA uses coconut coir, a special fertilizer infused silica clay called Arcillite, with a naturally high CEC for their space station tests.
The deep water culture system is the least expensive and easiest to maintain and expand hydroponic gardening.
Step-by-Step Guide to Making Your Own Deep Water Culture Hydroponics System
Ensure the Styrofoam™ has enough room to move up and down by cutting it to fit the container.
Add at least 5 inches of water to the container, tracking how much you add.
For each gallon of water used in the hydroponic garden, add two teaspoons of water-soluble fertilizer, such as a balanced 20-20-20 fertilizer with micronutrients.
- Add Epsom salt (magnesium sulfate) to the water at a rate of a teaspoon per gallon.
- Cut 2.5-inch holes into polystyrene boards for 3-inch net pots (or 1.75-inch holes for 2-inch net pots). Pot size selection is based on the mature plant’s expected stem girth. Net cups should not stick out and fit snugly into the polystyrene board.
- Space holes 12 inches (30 cm) apart and 6 inches (15 cm) from the sides.
- Stake seedlings with toothpicks and plant them with some of the initial germination soil. Ensure there is an opportunity for the roots to access water without being submerged – they still need to breathe.
Maintain the water level by adding water that has been preconfigured with the required nutrients.
Hydroponic gardening is an excellent way for children (and adults) to observe how temperatures, light levels, and humidity affect a plant’s water use.
I grow my outdoor hydroponic garden under a 30 to 50% shade cloth and closely monitor water levels after a downpour.
I adjusted the nutrients accordingly if the rain added quite a bit of water.
The water culture system is open, meaning I discard my hydroponic garden’s used water onto my garden beds after every harvest.
Without a doubt, this is the most straightforward gardening I’ve ever done.
The NFT System (Nutrient Film Technique)
The nutrient film system is one of the most common hydroponic systems, maybe only second to the ebb and flow system.
Both use gravity as their primary flow system, allowing nutrition-laden water to flow over the plant’s root tips and grow.
Water and essential elements are monitored and continually adjusted in this closed-loop system.
Micropumps connected to dissolved nutrient concentrates adjust the levels of all 19 essential plant nutrients on the run.
The nutrient film technique allows growing plants to absorb their required nutrients, and because the environment is uniform, plant growth is uniform too.
The Ebb and Flow System
As I said, ebb and flow systems are similar to NFT. Water flows through sealed pipes that prevent airborne contaminants from entering the system.
Holes in the pipes or ducts give plant roots access to the nutrient solution.
As the name suggests, the difference in this hydroponic system, unlike the NFT system, is that the water supply is intermittent.
Pump Timers And Switches To Control The System
A timed pump switches on and off at different intervals, catering to a plant’s varying day and night water needs.
We know plants grow through photosynthesis, using water, CO2, and light to make glucose.
The ebb and flow method gives the plant more water when the lights are on and less when the lights are off.
Light variation plays a vital role in flowering plants, though a few plants (like tomatoes) are not affected by photoperiodism – but more on that in a different article.
Most plants have a circadian cycle, where day and night are linked to growth and flowering cycles, which varies for different plants.
Hydroponic plants benefit from getting what they need when they need it, including other nutrients, light levels, and water.
Even CO2 levels are substituted for a fast-growing plant and generally kept under LED grow lights.
The Drip System
A continuous or intermittent water flow over the foot tips represents the liquid category of hydroponics.
The drip system is an aggregate system and uses pipes to drip water onto the aggregate for access by growing plants.
Plants grown in an aggregate have particular pH requirements. The system makes use of tiny pipes that run the risk of blocking.
Still, The drip system is arguably the most widely used system for hydroponic growing.
Like the previous system, it too is timer-controlled and drips nutrient solution onto the base of each plant via a small drip line.
The Wick System
The wick system uses capillary action to draw water from a reservoir to the plant roots.
While I’ve read that it is best suited for smaller plants like lettuce, foresters use the wick system, complete with biodegradable reservoirs, to establish saplings.
The wick system is incredibly viable in environments where growing plants are challenging, like deserts, where it’s used to establish palms.
Though not a transitional hydroponics system, the tree establishment project uses this ingenious system to provide plants with enough water to establish their root systems.
The Aeroponics System
The Aeroponic System is probably the most high-tech solution to growing soilless plants. They are grown media less.
This hydroponics system uses nutrient solution misters to irrigate the roots. The only growing medium is in the net pots.
Misting cycles are timer controlled, much like other types of hydroponics systems.
The aeroponic system needs a short cycle timer that runs the nutrient solution pump for a few seconds every few minutes.
Most indoor hydroponics systems require extensive capital investment, including an intelligent lighting system, to provide the optimal environment.
The benefit for commercial growers is that every aspect of the plant’s growth can be monitored, and interventions are done remotely via control panels.
There is no distinct labeling for hydroponically grown vegetables in the Netherlands, where hydropic gardens are commercial.
Frequently Asked Questions on Hydroponic Plants
What plants grow well in hydroponics?
The following plants grow well hydroponically. Beans, Basil, Blueberries, Anise, Caraway, Cantaloupe, Beet, Chives, Bell Peppers, Bok Choy, Coriander, Cranberries, Celery, Dill, Currents, Kale, Fennel, Grapes, Lettuce, Mint, Cucumbers, Okra, Oregano, Raspberries, Peas, Rosemary, Strawberries, Radishes, Sage, Watermelon, Savory, Spinach, Spring Onions, Thyme, Tomatoes, Zucchini.
What is the easiest plant to grow in hydroponics?
The easiest plant to grow in hydroponics is lettuce. Because it is short and compact, it does not require any support systems. Leafy greens such as collards, Kales, and chards are also very close to this top spot. However, you can grow most vegetables this way.
Which plants are not suitable for hydroponics?
Most crops can grow in hydroponics, but root vegetables struggle and do much better in the soil. Even so, Nasa was able to grow potatoes with this method. Also, crops like corn, wheat, and other tall plants would struggle due to having no support system.
Are hydroponics worth it?
Depending on the vegetables you wish to grow would decide whether hydroponics is worth it. This being said, hydroponics has fewer pest and disease issues. It grows crops faster and uses less water than conventional soil growing methods.
Do you need special seeds for hydroponics?
You can use standard vegetable seeds when growing in hydroponics. The difference would be the pots and the media you start the seeds off in. Initially, you may sow the seed into Rockwool or Perlite to get them going later, moving them into the hydroponic system.
What are the easiest plants to grow hydroponically?
The best plants are leafy greens like lettuce plants and spinach. Swiss chard is also easy to grow hydroponically. Not-so-easy plants to grow hydroponically are taproot vegetable plants.
Which is the most straightforward system to start hydroponic gardens with?
The deep water culture system is excellent because it has little investment and allows you to check plant progress quickly. This way of growing plants is more accessible even than soil growing.
Do hydroponically grown plants taste as good as their conventional gardening counterparts?
The organic environment of plants and animals affects the taste. Just as cows’ milk reflects what they’ve been eating, plants grown in different soils have different tastes. Whether plants grown hydroponically taste better is subjective.
I want to show my kids how plants grow in a hydroponics garden – any advice?
Use the floating system detailed above, but do it in an empty aquarium.
Unlike most plastic containers, the sides are square and transparent, allowing the board to float up and down as water levels change.
The whole process is visual, including the tiny bubbles from the airstone.
Remember, you can use the same water multiple times; keep adding nutrients.
Other than the plants listed, what other vegetables are worth growing hydroponically?
Other vegetables include the Fabaceae family ( the peas), but you must support these plants as they vine. Beans are super easy to grow.
Summing Up What Plants Are Best Grown in Hydroponics
It isn’t much you can not grow in a hydroponic system.
I love growing chilies like this. Hydroponics has faster growth and fewer pests and disease.
You really should give it a try.