Can You Grow Trees Hydroponically [Which Ones?]

Hydroponically growing trees is not so much an issue of whether you or cannot, but more of an issue of why would you? Is having the fruit of a tree within arm’s reach enough to overcome the challenges of growing one hydroponically?

In theory, any tree can be grown hydroponically. However, only smaller tree species and dwarf trees made via grafting are the only ones viable. Growing a full-sized tree is possible but it requires a considerable investment in a system that can support the weight as well as nutrient, water, and light requirements.

One has to ask what tree they would want to grow and if their hydroponics system can handle it. Let’s delve deeper to see if this all worth the hassle or should we just stick to the hydroponic staples of lettuce, tomatoes, and strawberries

Growing Trees Hydroponically: It is Possible

Many gardeners attempt and succeed in growing trees hydroponically. This is possible despite the challenges.

As evidence, take this dwarf fig tree grown hydroponically in a 3-inch net pot standing around 8 ft. tall. In the video below, it is clear that hydroponically growing trees is possible. Likewise, the nutritional requirements are also reasonable because it requires a standard hydroponic nutrients solution formula. The nutrient balance is maintained at 800-1200 ppm.

Hydroponic Fig Yielding Tons of Fruit

In the academe, this proof of concept has some foundation. A study conducted by Japanese researchers concluded that yield can be doubled when figs are grown hydroponically.

In the commercial space, in a surprising twist, it is Disney World in Orlando, Florida that has a visible working example of the principle where a giant tomato tree is grown – its heavy branches and fruits supported by nets.

Which Trees Can Be Grown in Hydroponic?

The experience in growing trees in hydroponics demonstrates that : (1) it is possible to grow trees hydroponically; (2) the nutrient and growth requirements are reasonable; and (3) smaller trees or dwarf trees are better suited to growing hydroponically.

The first conclusion means that any kind of hydroponics technique is viable in growing hydroponics trees. Deep water culture (DWC), nutrient film technique (NFT), and flood-and-drain technique, among others, will work as long as the growing requirements are met.

The second conclusion means that hydroponically growing trees may not be as demanding if they are reasonably small in size. We recommend small trees or dwarf trees for growing in hydroponics. This means standard pH, electrical conductivity, and nutrient balance principle applies.

The third conclusion means that smaller trees or dwarf trees would be better suited since they can be easier supported by a conventional hydroponics system made with polymers and PVC.

Techniques To Grow Trees Hydroponically

As stated before, smaller trees and dwarf trees are best suited to growing hydroponically. It is even better that they are fruit bearing to give some benefits to offset the cost of growing hydroponically (i.e. cost of water, electricity, and nutrients).

A grower can either elect an innately small tree to grow and then prune it; or produce a dwarf tree via grafting.

Small Trees and Pruning

Small trees have been selectively bred to maintain their typical size. They can be made even smaller by pruning budding leaves or growing branches.

Examples of small trees include the certain varieties of the jaboticaba, the plum tree, and the citrus trees (i.e. lemon, calamansi).

Creating Dwarf Trees via Grafting

Dwarf trees are the result of horticultural techniques. In this case, the most common method is via grafting. Grafting is a process whereby a stem of a plant is cut (scion) and inserted into the stem of another plant (stock) to produce a plant which combines the quality of both.

In theory, any tree can be made into a dwarf tree via grafting. Notable examples include apple trees, orange trees, and plum trees.

Worst Trees to Grow Hydroponically

The worst trees to grow hydroponically are all those trees that can grow large. Generally, anything above 10 ft. may be difficult for a normal hydroponic system to sustain and support.

If they are non-fruit bearing it is even worse because there will be no fruits which will offset the cost of maintaining the system for any reasonable amount of time (if not for the sake of having it).

Both hardwoods and softwoods alike are not viable if their size exceeds anything beyond reasonably small for a hydroponic system to sustain. In general, anything which grows more than 10 ft. is not viable.

5 Problems in Growing Trees Hydroponically

Conventional trees are less suited to be grown in a hydroponics system because of their innate size and growing requirements. These factors would entail increased cost in setting up and maintaining the system.

1 – Space

As a reference, a medium sized tree ranges from 20-40 ft. Even trees smaller than what is considered medium sized are still quite large for growing hydroponically. This large space will be devoted for ventilation, humidity, and temperature control.

Given that hydroponics seeks to maximize space utilization and yield by growing multiple plants (sometimes stacked on top of each other) by removing soil limitations, it is counterintuitive to have a single purpose system.

2 – Roots

Trees rely on large roots systems for nutrient uptake, water uptake, and stability. There are three types of root systems for trees (1) taproot, (2) heart root, and (3) lateral root.

Tap root systems grow from a central root which provides the central support from where all other roots diverge from.

Heart root systems, also known as oblique roots, are roots which grow diagonally and form a mass of roots that acts as a counterbalance to the tree’s weight.

Lateral roots systems grow outwards slightly beneath the ground. About 80% of trees have lateral root systems.

The problem with any tree root system is that they take a fair amount of space and may not be supported by a normal sized grow tray. This makes it ill-suited to hydroponics which prefers thinner, more pliant root systems which can fit in net pots or reach the nutrient solution.

Worse, trees with shallow roots systems sometimes have buttresses which are wide, tall, roots, protruding from the ground to keep the tree from toppling over. These kinds of trees are even worse for growing hydroponically

3 – Structural Stability

Given that small and medium trees are already quite large, the structural stability needed to support the entire mass of a tree system must be equal to keep it upright.

Plastics, though versatile and strong, are not so strong to support an entire tree system. The usual PVC and food-safe material of most hydroponic systems are unable to support the mass of an entire tree system. Likewise, an hydroponics system cannot anchor a tree unless the system is bolted on the ground (very unlikely).

4 – Nutrients and Water

Trees require an extraordinary amount of nutrients and water. Sources vary on the nutritional and water uptake of trees due to the differing trees observed.

A study on sessile oak in Eastern France reveals that the maximum rates of daily water use range from 10-200kg per day for trees that average 68.89 ft. (21 m) in height. The USGS states that a large oak tree can consume 400 gallons per day.

Nutritional requirements of trees vary between species so there are no specific numbers agreed upon by experts. A fair estimate given is that a tree consumes around 40 gallons of dissolved nutrients per day.

Given that hydroponics uses 10 times less water compared to conventional soil cultivation according to the National Park Services, water and nutritional requirements are lessened but there are no studies to conclusively confirm this notion.

5 – Lighting

The massive size of trees necessitate plenty of light to grow. It has been estimated that trees require ~24,000 calories of light energy per day. This energy is used for photosynthesis, cellular respiration, and other biological processes

Given the light requirements of trees, growing trees hydroponically outdoors is more viable than indoors unless it’s in a greenhouse setting or with the assistance of grow lamps. The light necessary to give adequate sunlight exposure to all parts of a tree is vital in hydroponically growing trees.

Growing Bonsai Trees Hydroponically

Bonsai trees are well-suited to hydroponic application. Their small size due to pruning makes them perfectly viable in small hydroponic systems. Some bonsai trees are even smaller than some net pots!

Aqua bonsai is a growing trend in the bonsai community. Bonsai trees are grown without the presence of soil. Instead, a nutrient-rich solution is used as the substitute for soil. This is similar to the Kratky method in hydroponics which operates on similar principles.

Given the success of aqua bonsai which is effectively the equivalent of the Kratky method, other hydroponics techniques can find application. By extension, deep water culture (DWC), nutrient film technique (NFT), and ebb and flow technique, among others will apply.

Takeaways

1. It is not only possible to grow trees hydroponically but completely viable given a few conditions.
2. The viable trees are those which are innately small or dwarf trees created by the process of grafting.
3. Growing full-sized trees is possible, however, these require a significant amount of investment to set up and maintain which is not practical for the average grower.

Sources

• “3 Types of Tree Root Systems” by Sophia Huang in A•Plus Tree Care & Sustainability
• “A review of whole-plant water use studies in tree” by Wullschleger et al in Tree Physiology
• “Aqua Bonsai” by Daisuke Nakajima in Bonsai Empire
• “Double Cropping of Fig under Hydroponic culture” by Kawamata et al in Engei Gakkai Zasshi 71(1): 68-73
• “Evapotranspiration and the Water Cycle” by n/a in U.S. Geological Survey
• “FAST-GROWING TREES FOR PRIVACY” by Zone in Davey
• “Grafting and Budding Nursery Crop Plants” by Bilderback et al in NC State Extension Publications
• “Hydroponics: A Better Way to Grow Food” by n/a in National Park Service
• “Process of How Trees Absorb and Evaporate Water via Roots and Leaves” by Steve Nix in Treehugger
• “Tree Root Systems” by Sherry Rindels in Iowa State University