What is Hydroponics?
One of the main problems with soil-based farming is that natural fertilizer can be inconsistent and usually includes pests. Hydroponics (which in latin means “working water”) is growing plants without soil. Supplying the essential nutrients dissolved in water. Aiming to create the perfect plant root environment and deliver the perfect balance of required nutrients in a pest-free environment.
Most people think hydroponics is complicated and above their skill level. But in reality hydroponics is super simple and a large number of people are already farming and gardening at home using the technique.
History of Hydroponics
Although there are reports of hanging garden baskets in ancient Babylon. The first recorded experiments where in 1699 and are attributed to John Woodward. John studied various types of water to see if he could get mint to grow, but concluded that soil was needed (cropsreview.com). It wasn’t until the 1860’s when German scientists Knop and Sachs developed synthetic solutions of plant nutrients that real progress was made. Then, in the 1930’s Dr W.F. Gericke began using hydroponics commercially in California. Which led to growing food for troops in World War II.
Those early successes and research has helped shape hydroponics into what we know today.
Benefits of Hydroponics
- More efficient water use
- Since nutrients are delivered directly to the plants roots, up to four times as many plants can be grown in the same amount of space (This is because the plants are not competing for nutrients as they would in soil)
- Can grow all year with indoor growing or greenhouses
- No risk of soil-borne diseases
- Plants usually grow bigger and faster
- Works in areas where it is not practical for growing such as Alaska’s harsh winters or the desert heat
- No weeding
- Can be placed at a raised elevation for people with a bad back, or physically handicapped
- Can be used indoors in education to teach children plant life cycles
- Crop rotation is not required
- Good and bad conditions have fast results
- Not all plants can be grown with hydroponics
- Shared nutrient solutions can spread problems quickly
- Need a level of knowledge and skill for successful production
- Can be costly to setup (but can also be really inexpensive)
What Plants You Can Grow Hydroponically
If you’re asking, “what can be grown hydroponically?”. You might be surprised that aside from fungi and mushrooms, most herbs, vegetables, and flowers can grow hydroponically.
Lots of herbs will do well grown hydroponically. The best herbs to grow are
- Anise – This annual herb is very small and has thinly cut serrated leaves with whitish flowers that are arranged in flat clusters. Should be planted after all threat of frost is passed and usually grows rapidly from one to two feet high. When plants are large enough the green leaves can be cut and seeds gathered after one month of flowers blooming. You can use the Anise leaves as a garnish, in salads, or put the seeds in cookies or cakes.
- Basil – You can actually grow basil year-round in a protected environment, because it grows really well hydroponically.. It can be trimmed and harvested weekly once mature.
- Catnip – A perennial mint family herb that does well in partial or full sun. Usually grows three to five feet tall. Easy to propagate with stem cuttings, root ball division, or seed. Sow the seeds in the early spring or late in the fall in plugs. Finished plugs generally take 8-10 weeks.
- Chamomile – Does well in soilless growing. Has medicinal qualities and often used to make chamomile tea. Likes full sun outdoors but can handle some shade. Finished plugs generally take 4-6 weeks.
- Chervil – Chervil likes cool temperatures and low light conditions. Otherwise it can grow very slowly or bolt. Which makes it a great winter crop. Usually takes four weeks to harvest.
- Chives – Hardy plants that are a relative of onions. Produce a continuous supply of seasoning that you can use in salads in small spaces. Grow in a variety of conditions and give off a very aromatic smell that high-end cooks love.
- Cilantro – Can tolerate low light conditions and a variety of pH levels. It’s a relative of parsley and requires some maintenance to reach harvest stage in 6 weeks. Will go to seed if not trimmed regularly.
- Coriander – Another parsley type herb which is cilantro that is allowed to go to seed. Does best in full sun. Usually only the small immature leaves are harvested as the large mature “feathery” leaves are not desired. Cut tops to crown and allow to re-grow for harvesting.
- Dill – Dill can be continually harvested and keep on growing. Although it is recommended to replace spent plants every 3-4 weeks.
- Fennel – Usually grown as an annual, but is actually a perennial plant. Typically grows 3-4′ tall and looks like Dill. For best eating tender stalks just before they blossom. Use seeds in vegetable dishes or cheese spreads.
- Lavender – A fragrant shrub or herb that is usually grown outdoors. Used in perfumes, essential oils, lavender water, aromatic vinegar, etc. Propagated by cuttings. Harvest in 20-26 weeks after seeds are sown.
- Marjoram – Usually grown as a annual, but is a perennial. Often used in meat dishes or salads. Does well in full sun and is very fragrant. Best sown in greenhouse flats then transplanted.
- Mint – Most mint (like orange, peppermint, and spearmint) are actually perennial aquatic plants and do best in shallow streams or ponds (ideal for hydroponics), but also grows on land.
- Oregano – Hardy perennial that has stems that sprawl up to two feet tall with small white or pink flowers. Cut back foliage to stimulate, and propagate by division or seed. Will need to be replanted every 3-4 years with plants become woody. Can be used on meats like lamb, pizza flavoring, or other sauces.
- Parsley – A long tap root herb that grows well in 12″ or deeper hydroponic containers.
- Rosemary – A sub-shrub that is a hardy evergreen grown for its leaves in culinary applications. Can grow up to six feet tall, but don’t do well in the cold. Will tolerate some shade but does best in full sun.
- Sage – Another hardy sub-shrub. Grown for seasoning rich meats and salad dressings, or flavoring cheese. Care must be given to allow up to three feet in diameter between plants. Harvest and dry leaves prior to blooming.
- Tarragon – A 2-3 foot tall perennial herb that is typically used in seasoning such as vinegar. Prefers moderate sun and shade. Gives off a slight aroma until leaf harvesting when the oil will start to product a sweet unique tarragon smell.
- Thyme – A sweet herb in the mint family. Can be used in seasoning or as a border plant. Is very hardy and should be planted in spring. Prefers full sun and only requires a small amount of fertilizer.
- Watercress – European perennial of the mustard family that is low growing with flower buds. Sow in pots then transfer to water. Has many medicinal, decorative, and culinary uses.
Most flowers can be grown in a hydroponic garden. They can be grown in large numbers and once mature enough can be transplanted outside or cut.
Hydroponic vegetables are broken into two seasons, warm and cold.
Cool season crops
Cool season crops have two growing seasons. One in early spring (late February) and one in early fall (late August).
- Cauliflower and broccoli – Broccoli is a perennial in the cabbage/mustard family and has big flower heads with branches similar to a tree and an edible stalk. Heavier than other plants and will need stakes to remain upright. Cauliflower is in the same family as broccoli, cabbage, collard greens, and kale. A support for the roots is important to allow the roots to touch the nutrient solution and nothing else. These two plants are the most cost effective to grow because they don’t need a constant supply of nutrients and can grow in lower temperatures.
- Lettuce – Semi-headed or leaf lettuce does the best grown hydroponically. Species like butter, bibb, simpson, black-seeded, and Boston. Likes cooler temps and may need additional light.
- Bo choy and cabbage – Can be grown in rockwell cubes or purchased as seedlings. Once they can stand on their own transfer to hydroponic pots. Then, surround with growing medium. Note – Cabbage can spread out into a large area depending on variety and should be allowed up to two feet to expand.
- Swiss chard
- Spinach – Best started in rock wool in ebb and flow systems. Needs oxygen in the roots so you should raise them up a bit. Once ready for transplant move them to their permanent location. Needs 20″ per spinach plant. Be careful to not use too much light and to use the right nutrients.
- Snow peas, sugar snaps, and peas – Mainly a cool season crop in spring or fall. Depending on what type of peas you plant they usually take 3 weeks to be harvested when they start to flower.
- Carrot stubbies
- Green onions
Warm Weather Crops
Seedlings should be started in March to April and transplanted in May. Harvesting is done in August.
- Green peppers – Prefers warm temps and growing conditions like tomatoes. Will require staking to help stabilize. Varieties that do well hydroponically are gold frame, Narobi, Fellini, mazurka, cubic, for sweet peppers and for hot peppers habanero, cayenne, and jalapeño.
- Tomatoes – Transplants will generally do better in hydroponic systems than seeds. We suggest disease resistant varieties like Daniela or Trust and cherry varieties like Sweet 100s and Cherita. Heirloom varieties such as Thessaloniki and Moskvich. Will need support or staking and need nutrients flowing into the root system 4-6 times a day. May need additional lighting for increased production. Can be pollinated with a gentle shaking or vibration stems with blossoms.
- Eggplants – Best planted in early spring in full sun like tomatoes, but do better in warmer temps. Needs 60 – 100 days to become mature enough to transplant.
- Green beans – Plant in growing medium and water from below with a air bubbling system. Beans require a similar nutrient formula to other vegetable crops so nothing special is required. Bean seeds will germinate around 16 days and grow plump quickly.
- Cucumbers – A great fall crop due to how quickly they grow. Does best with a constant supply of nutrients and water, and high humidity, light intensity, and temperature. Under correct environments they will produce and grow rapidly.
- Melons (requires more space)
- Squash (requires more space)
Other vegetables can be grown hydroponically, but may require extra care. Such as potatoes, radishes, onion, carrots, parsnips, etc.
Crops to avoid all together are summer squash, zucchini, vining plants, and corn. These crops aren’t space efficient and you’re better off with other crops that are more compact to get more yield per sq. ft.
There is a large variety of fruit plants that can be grown hydroponically like:
- Raspberries – May require additional space
- Blackberries – May require additional space
- Blueberries – May require additional space
- Strawberries – Produce well when grown hydroponically. Can be grown year round to feed a family of four. Ensure the runners you use are virus tested and certified.
- Lemons (requires additional resources)
- Bananas (requires additional resources)
For most people a greenhouse is not an option. The cool thing about hydroponics is that you can use virtually any space you like with grow lights. Giving you flexibility to grow in spaces you never could have imagined with traditional methods. Such as a basement.
Just make sure whatever space you choose has adequate ventilation, and humidity. Plants need humidity for the process of photosynthesis involving giving off moisture (transpiring). Be careful not to exceed 85% relative humidity to avoid stressing the plants. Monitor humidity with a simple and inexpensive humidity gauge (here’s one on Amazon).
Types of Systems
What type of system you use will be based on the plants you want to grow, along with the size and space available.
Non-Circulating Hydroponic System
The non-circulating hydroponic system is one of the cheapest and easiest ways to get started growing. Using no water pumps, aerators, specialized knowledge or equipment, and requires very minimal maintenance. Made popular by Bernard A. Kratky ( aka the Kratky Method) with the publishing of these articles, PDF, PDF.
Seedlings will be planted or transplanted in a net cup with growing medium such as Hydroton. Nutrient solution fills the container to a certain point below the plant, but in contact with the medium. The medium will wick moisture up for the plant to grow. As the plant grows it develops roots that dangle into the water. No longer touching the medium to allow for oxygen. The roots will continue to get longer as the water level goes down and creating a larger air gap.
Growing is complete when less than 10% of the original solution is left in the container.
Non-circulating hydroponics is great for educational institutions.
Kratky hydroponics systems video:
Water Culture Hydroponic System
The water culture systems are pretty simple. Generally consisting of a pump and air-stone, plant holders, and a container for the nutrient solution (aquariums are commonly used).
Pots can be placed on a wooden board with holes drilled, or inserted on a floating styrofoam raft.
Place the air pump next to the tank. The connected air line and air stone gets placed in the bottom of the container.
Add nutrients in a separate opening or pot supporter.
The disadvantages of the water culture system is that it doesn’t perform well for growing larger plants such as tomatoes.
Example water culture hydroponics system video:
Drip Feed Hydroponic System
The drip-feed hydroponic system is popular with commercial growers. Nutrients are dripped into the top of the medium that contains the plant. Usually at a rate of 25% more than the plant needs for proper nutrient balance around the roots.
Flood and Drain Hydroponic System
Also called the “Ebb and Flow” system the flood and drain system will periodically (timer controlled) flood the growing tray with nutrient rich water and drain away. This is usually done a couple times a day to keep the roots and medium correctly moisturized.
When the solution floods the growing tray it forces out unwanted gases from the plant roots. Then, as the water drains air is pulled in to oxygenate. Leaving the roots with all the nutrients it needs along with a good amount of air.
Flood and drain is an energy-efficient system since it doesn’t run constantly. If your area is prone to power outages you may need a battery backup or solar panel kit to keep your roots from drying out. A growing medium that helps retain moisture like Rockwool will also help with this.
Example Flood and Drain hydroponics system video:
Nutrient Film Technique
Most people envision this system when they think of hydroponics. It doesn’t need a timer because the water is constantly flowing with nutrients. NFT doesn’t use a growing medium and plants are grown in containers or pots that allow the roots to dangle in the water to soak up the nutrients. A sheet of glass is also commonly used.
NFT is the most ideal with a reliable power source. You can also use a 12 volt battery and solar panel.
Example NFT hydroponics system video:
Similar to NFT the aeroponic growing system will allow the plant roots to grow without a medium. A mist is regularly sprayed on the plants to prevent them from drying out.
This requires a reliable power source or solar panels since the plants need misting every couple of minutes.
Example Aeroponics system video:
The cool thing about the wick system is that there it has no moving components. There is a solution containing nutrients that gets sucked into the growing medium similar to a oil wick.
This is a very easy system to build if you have the time and skills.
Disadvantages of this system is large plants may consume nutrients faster than the wick can supply them.
Example Wicking hydroponics system video:
If you’re just starting out a pre-built hydroponic garden system might be your best bet. The kits are ready to grow and will help you get started while minimizing losses.
Over time you can study the system and how it works. Do some small tests using your own system and expand over time.
Hydroponic systems can range from a mini greenhouse to a simple low cost bucket system. Most kits will come with air stones and pumps, sphagnum moss, grow lights, growing medium, and nutrients.
Selecting the Correct Air Pump
The two main air pumps to choose from are non-submersible, and submersible. Submersible pumps will sit directly in the water and the non-submersible will be located outside the water and kept dry.
The size of pump will be dependent on the size and type of the hydroponic garden.
Larger pumps will also generally have the option to connect multiple air lines.
Make sure to use total dynamic head when sizing your pump. This will give you an accurate water flow at the height and distance the water travels. Here is a total head calculator you can use.
Since you most likely will not have the sun to grow your plants you’ll need special grow lights.
High pressure sodium (HPS) bulbs can be used. These bulbs give off a yellow light and used to supplement other grow lights or during the reproductive stages of plant growth. If used as the sole light source your plants will end up unhealthy, pale, and the heat will make them tall and “leggy”.
Fluorescent growing lights are popular and give off a red and blue light spectrum that mimics the sun light spectrum. You can also use compact bulbs instead of tubes for tight spaces. Also adding a reflecting hood will help make them more efficient.
LED lighting is fairly new in the hydro market. They are generally more energy-efficient, produce less light, and cooler temperature which allows them to be placed closer to the plant without worrying about burning leaves or stalks. Higher in cost but make up for it in electrical savings and lifespan.
Again, your garden size will dictate the lights that you need. Here are some estimate to give you a general idea.
- 18″ x 18″ area will need 100 watts
- 2′ x 2′ area will need 150-175 watts
- 3′ x 3′ area will need 250 watts
- 25 sq. ft. of growing area will need 400 watts
- 36 sq. ft. of growing area will need 600 watts
- 64 sq. ft. of growing area will need 1000 watts
Lighting is just as crucial to the success of your garden as nutrients. Choose wisely.
Instead of soil hydroponics uses special growing medium (unless you’re using a technique like NFT that doesn’t require any medium) which helps plants absorb nutrients and support root systems. Common types of medium are:
- Hydroton – Made by heating ordinary clay until it forms into clay pellets like popcorn. Retains water well and can be used for multiple crops. Although you should sterilize it between crops.
- Coir – (sometimes called coco peat) Made from coconut shell fibers. Looks like dirt, but in block form with no minerals in it. Hydroponic farmers will sometimes mix it with perlite to improve drainage.
- Perlite – Created by heating silica until it expands. Often used as a filler due to its low cost and weight. Improves drainage.
- Rockwool – Made from molten rock or basalt and come in bundles of spun fiber. It cannot be used multiple times, but is very efficient.
- Sawdust – Decomposes
- Hortifibre – Decomposes
- Vermiculite or straw – Decomposes
The type of medium you choose will depend on what you want to grow and what system you’re using. Sometimes a mix of different types of media will be best.
Media must be completely inert, well-draining, and pH controlled. Media will give you a good ratio of air and nutrient solution.
Plants generally need three main nutrients;
- Potassium – Help plants synthesize protein and produce sugars and starches to support growth
- Nitrogen – Helps form enzymes, amino acids, and chlorophyll
- Phosphorus – Helps produce starch and sugar to provide energy to produce fruit and flowers along with root growth
The particular needs a plants and stages of growth will vary the needs of each nutrient required by the plant.
There are also micro nutrients that help plants grow;
- Calcium – Helps form healthy cell walls
- Boron – Helps form healthy cell walls
- Magnesium – Creates oxygen and stimulates growth
Once you know what type of plant you want to grow, you can buy liquid or powder nutrients to mix into the system. Buying powdered nutrients and mixing them with water yourself can save you quite a bit of money. Although it does require some knowledge and is not as convenient as ready-made liquid. Which is why liquid nutrients are more common as the concentrated formulas are easy to store and and handle. Liquid formulas also typically have a pH buffer so you won’t have to mess with trying to balance the pH yourself. Which is important because without the proper pH plants can’t absorb the nutrients it needs.
A general pH range for healthy plants is 5.5 to 6.0.
Most nutrients will provide a chart that tells you what different plants need at various stages of growth.
Each plant has its own “taste”. Some will need more phosphates, while another may want more nitrogen. You will need to take this all into account. As too much nitrogen can “burn” plants and too little may stunt them.
An issue with powered plant food is that it may nor dissolve properly. Causing problems with ayirstone or pumps. Also, the dry food usually doesnt have pH buffers. So you may need other supplements to get the pH range you need.
Test strips are an easy way to check your nutrient pH level. There are also liquid test kits that you add a dye to a tube to see what color it turns. Comparing the color to a pH chart to get the corresponding pH level.
You can also buy a digital pH meter (here’s a popular one on Amazon). This makes things a little faster and easier. With a touch of a button after dipping the electrode into the water you’ll have a pH level on the screen. For the most part these testers are pretty accurate, but do require care to properly function. And should be tested every now and then with a known pH solution to verify readings.
For the most part, most systems will run themselves. But like anything you’ll want to keep an eye on things and catch any small problems before they turn into large ones.
One common problem new growers face is plant instability. Plants will lean over and falls since they are not in soil once they reach a certain height. This is easily fixed by using stabilizing supports.
There are also some daily tasks to make sure the right conditions are continuing for proper plant health.
- Check the humidity on a daily basis – as mentioned earlier you want enough to replace moisture plants lose, but not too much so the plants are not stressed
- Inspect flooding and drainage so plants are not drowning or drying out
- Inspect water levels which can change fairly fast in warmer temperatures due to evaporation
- Look for any insects or mites that may be attacking the plants. But before taking action make sure you know which bugs are good and which are bad. For example dragon flies and spiders are good and should be left alone (although allow them a path to go outside if your garden is indoors)
- Check ventilation and temperature
- If you have a NFT system double check root length and trim if needed
- Replace nutrient solution around twice a month (use the old solution to water another garden or indoor plants and flush the system of salt)
It is a good idea to keep a daily log. That way you will be able to easily spot anything that is not normal.
Hydroponic farming can be a great way to economically grow sustainable organic food. Start small and expand over time and experience it for yourself before making a judgement.
University of Florida – Article
Mexican Hydroponic Society – Website