What You Cannot Grow in Hydroponics? The Worst [and Why]
You can grow almost anything hydroponically, they say. But is this really true or just an exaggeration?
Almost any plant can be grown hydroponically. Leafy greens and herbs are the best because they are versatile and easier to grow. However, some plants such as trees with deep roots, root crops, or plants which bear large fruits are more difficult to grow hydroponically due to space and support required.
The truth is that you CAN grow almost anything hydroponically but there is a lot more information needed to know which plants are best and worst to grow. Considering which hydroponics technique to use will prove beneficial in the long run.
Can You Grow Almost Any Plant Hydroponically?
The wonders of hydroponics is that the sky’s the limit. There are no rules.
The general principles of hydroponics consistently remain the same – water as the medium for nutrients. You can work around that general principle to implement and refine hydroponic growing techniques and adapt it to different plant types.
Even trees can be grown hydroponically. In 2005, 2 Australian growers proved that full papaya trees can be grown in a hydroponics system. In China, tuberous roots and a 500kg pumpkin were grown in vertical farms in an effort to meet increasing global food demand in the future. In Japan, large melons are being grown hydroponically and harvested for the local market.
But just because you can grow something hydroponically, doesn’t mean you should.
These techniques might be applicable to industries and research institutions that have the space, capital (often through external funding). However, but the average grower will experience serious difficulties to grow trees or any very large plant hydroponically.
Which Plants Are The Worst To Grow Hydroponically?
Despite any plant can be grown hydroponically, many of them are not practical for such a system.
In general, any plant that has heavy fruits or crops, thick roots, and a large build are not suited for conventional hydroponics. These take up too much space and resources to grow sustainably.
Trees are difficult to grow hydroponically for the reason that they are big, heavy, and often have thick roots which go either very wide or very deep which cannot be sustained in a hydroponic system that does not have the required space.
Trees require massive amounts of nutrients to grow and sustain themselves. They also require a lot of space to grow, a fair amount of ventilation to allow CO2 to be absorbed by the tree, and an adequate amount of lighting to induce photosynthesis.
There have been attempts to grow fruit-bearing trees hydroponically but these are often reserved for the dwarf versions of these plants.
What you can do is to start growing a tree hydroponically to then move it to soil in a large area.
One of the trees that can be grown hydroponically with a relatively small space is the fig tree. Figs root systems are adaptable and often shallow. They can either grow wide or deep depending on the medium it is in but will inevitably break out of a grow bed. Hence, larger grow beds are necessary to make sure that the roots have enough space.
Fortunately, its growing conditions are not that difficult to maintain and are similar to those of a tomato plant (you can use the same treatment or grow both of them together).
Root crops are difficult to grow hydroponically because the edible portion of the crops is situated on the roots. These plants require plenty of soil for the roots to spread and grow. Root crops include turnips, carrots, potatoes, radishes, and beets, among others.
The best way to grow root crops is through the Ebb and Flow because the water is cycled in such a way that the roots are flooded and drained to have proportionate amounts of air and nutrient-rich water. Ebb and flow system also allows for the roots to spread out in the fill tray.
Here is an example of potatoes grown hydroponically.
Plants with Large Fruits
In general, anything that bears large fruits is difficult to grow hydroponically. These plants include melons, winter melons, squash, and watermelons, among others.
Though difficult, it’s not impossible. It just requires more planning and careful implementation. The most common approach is to place supports to bear the weight of the heavy fruits such as a floating raft system or overhead support like in vineyards.
Here’s a Hydroponic Melon Greenhouse in Japan as proof of concept.
Which Plants Are Best To Grow Hydroponically?
Many are the plants that growers commonly grow in hydroponic.
In general, any plant that has smaller roots, size, and produces reasonably sized fruits are well-suited to hydroponics. These include leafy greens, herbs, and berry plants, among others.
Leafy greens include lettuces, kale, chives, endive, spinach, mustard. These are among the easiest to grow hydroponically and can be grown all year-round provided that the temperature and lights are regulated.
These can grow on any hydroponics system. The most popular techniques for growers are the nutrient film technique (NFT) system and deep water culture (DWC). They are low maintenance, fast growing, and high yield.
Herbs are well suited growing hydroponically and can be grown using any of the hydroponics techniques. They are relatively small, fast growing, and not delicate. Herbs include anise, basil, thyme, chamomile, oregano, and cilantro, among others.
These plants have similar growing conditions with an optimal pH level of 6.5 and EC of 1.2-2.
Basil is a versatile and popular option to grow hydroponically and should be your starting choice if you’re a beginner. It is a well respected culinary ingredient in many cultures that gives punch and flavour to many dishes. Luckily, YourIndoorHerbs has many articles regarding basil!
For growing basil, it is important to know that though they are easy to raise, it does not mean you should neglect their needs. Proper pruning and watering is a must. Soil should also be considered to make sure they grow healthy. Neglect may cause basil leaves to become transparent, or worse, die.
Berry plants are well suited to growing in any hydroponics system but are conventionally grown using an NFT system. Berry plants include tomatoes, blueberries, strawberries, and peppers, among others.
Berry plants often require relatively chilly temperatures at 72-74 °F (22-23°C) to grow so temperature is the biggest concern in growing them. In an NFT system, the optimum amount of sunlight is 14-16 hours and with low humidity. Studies have shown that a vertical four pipe system produced the best yield.
Here is a video as a proof of concept.
Which Hydroponics Method/Technique Is The Best?
If you ask 20 different hydroponic growers, you’ll have 20 different answers. Hydroponic systems which offer their own unique pros and cons compared to the other system. What matters is that the chosen technique is a good fit for the plant type and the user’s ability.
To help better inform you, here’s a quick rundown of the pros and cons of each technique.
Deep Water Culture (DWC)
This is the oldest of all the techniques and very reliable. The pros include an oxygen rich reservoir due to the air pumps and fairly simple set up consisting of a reservoir, grow tray, and air pump. The cons is that the system depends on the air pump to be effective hence prolonged air pump failures could be fatal.
Nutrient Film Technique (NFT)
This is a completely medium free system where the roots are placed in slightly sloped channels where a continuous or periodic flow of nutrient solution runs. The pros include options for a more vertical set up and no medium requirement. The cons include pump failure could lead to plant loss and its not suited for plants with larger root systems.
Aeroponics uses nutrient rich mist or fog operating 24 hours to provide hydration and nutrients to the suspended plants. The pros include that it is considered the most rapid growing method and has the least water consumption. The cons are that the technique requires high technical knowledge and a lot of observation to make sure the mist pumps are always working.
Wick and Kratky Hydroponic System
The Wick and Kratky systems are the easiest to implement. Both are passive techniques which means that there are no pumps or active components at play. The Wick system uses wicks to carry nutrients from the reservoir to the grow tray whereas Kratky places the roots directly over the nutrient rich reservoir. Since these methods are so passive, it is hard to check the reliability if the wick is doing its job or if the roots are getting enough oxygen.
There are other systems which also have their respective pros and cons and these should be considered when growing plants which are not conventionally grown hydroponically.
- You can grow almost anything hydroponically. The sky’s the limit.
- The plant type best for hydroponics are those which are small and have manageable root systems that can fit in a hydroponics system. Large plants or plants with large fruits
- Some hydroponics systems are better suited to growing some plants than others. Each system has its pros and cons that you have to consider.
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“Fig” by J. Morton in Purdue University
- “Green House Hydroponic Systems/Gallery Cultivation/Nft Mft /Hydroponic Trees for Vegetables Growing” by n/a in Made-in-China
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- “November/December 2005” by Geoff Wilson in GreenRoofs
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