Hydroponics gardening is an efficient method of growing smaller leafy veggies, herbs, and tuber plants. But can you grow an apple tree in a hydroponic system?
The short answer is yes, but with some terms and conditions. Growing an apple tree in a hydroponic system will require a specialized setup, and this will be a project that will take years. Also, you will need to grow a dwarf apple tree.
Full-sized tree species shouldn’t be grown hydroponically, as their root systems are too large and can’t handle the lack of growing medium anchoring. Also, their roots can land up choking healthy roots.
Gardeners can purchase dwarf species from the nursery. Dwarf fruit trees still produce full-sized yield, but due to their size, the number of apples you’re able to harvest will be limited.
But, it’s unlikely you’ll be able to find the exact dwarf apple tree you want for your system. You can always create your own if you can’t find a dwarf tree. Be warned it is a long process.
Growing Your Own Hydroponic Apple Tree
Growing an apple tree from seed will be a process that will take six to ten years to produce its first harvest. For most gardeners growing an apple tree from seed is a project that’s too long.
While you could dwarf this small sapling into a bonsai apple tree, again, this will take a very long time, as the seed tree will want to constantly reach its full potential. Dwarfing an apple tree will take significantly less time.
Dwarfing an apple tree will produce fruit within two years.
This process starts with sourcing a rootstock of an apple tree. Rootstock is the part of the plant that is under the soil. It’s the roots and stem of a well-developed plant - in some cases disease resistant and heavy producers. Apple rootstocks are now sized into classes. One is a dwarf tree, while a 10 is the standard size.
The rootstock you want is the very small trees that grow to 6 feet tall and are P22, M27, and G65. Each letter indicates where it originated from or the breeder.
P is designated Polish apple rootstock, which was bred to be winter hard.
G, or CG, designates Cornell-Geneva stocks which are those developed via the Cornell and USDA collaboration at the New York Agricultural Experiment Station in Geneva, NY. The "G" is the old designation.
And M is designated to the Malling series developed stocks. East Malling Research is a pioneer in the development of dwarfing rootstocks.
Almost all rootstock plants will be cultivated in soil, which means you’ll need to wash off the earth. You can immerse the roots to ensure all the dirt is removed, but don’t let it soak as the rootstock can drown.
Once happy, you can place the rootstock into Rockwool for support. When planting your rootstock into the hydroponic system, make sure not to increase the nutrient solution to ensure root rot doesn’t develop.
The next step requires taking a cutting, or a scion, from an apple tree, you like and merging, or grafting, it with the rootstock.
When taking a scion from the tree, ensure the grafting cut is taken at a 45° angle. Always make sure your secateurs are clean to ensure no diseases are transferred over. And when you’re ready to graft the scion to the rootstock, ensure the angle is also 45°.
Once mated, wrap the join with plastic tape. Grafting will take practice, and you’re bound to have a few failed attempts, but when it is successful, place the apple tree in a dark place for around four days.
The rootstock needs to be placed in a dark environment to limit water loss; also, the plant is building a new vascular system and cannot afford to lose water at any cost.
After the graft has been taken, you can expose it to light again, but keep monitoring it. Also, this is an excellent time to increase the size of the container to ensure that the rootstock’s growth isn’t stunted.
And when roots can explore, they can tap into more nutrient solution absorption. This will lead to a plant that is healthier and stronger.
When these steps have been completed, you will have to wait at least two years for the tree to reach its pollination stage. If you are growing it indoors, you will have to hand pollinate.
But if you are hydroponically growing it outdoors, bees and wind will pollinate the tree. Hand pollination can be accomplished with a paintbrush and spreading the pollen with the bristles.
Now that you know the processes involved in creating your own dwarf tree let’s talk about the perfect growing conditions for an apple tree.
Perfect Growing Conditions For Hydroponic Apples
When growing any plant successfully, you want to emulate its natural conditions. After all, it evolved to thrive in these environments. With growing any hydroponic tree, you will encounter three issues, space, sunlight, and water access.
All trees require these three elements in large quantities. When setting the timings for watering your tree, you will need to increase watering intervals five to ten more times a day than compared to other plants.
This nutrient solution will need to be tested for pH and nutrients. The pH levels will change depending on the apple tree you’re growing. Crab apples will require a higher pH level of around 6.0 - 7.5, while a regular fruiting apple tree will prefer a slightly acidic solution of about 5.5 - 6.5.
Growing medium for an apple tree will have to mimic the conditions of its natural habitat. Apple trees don’t like clay soil and prefer soil that is loose and drains well. While we say the ground needs to be loose it still needs to hold the tree in place.
When it comes to the hydroponic growing medium, you’re best using either rice husks/hulls, which are a byproduct of farming rice, a mixture of vermiculite and perlite, and finally, Rockwool (for the early stages). You will need to purchase this growing medium in bulk for the project ahead.
Fertilizer needs to be slow-releasing, as well as a low dose. Overfeeding your tree when it is young could cause root burn, which will hamper growth. Use a general food solution from your garden center.
Heat-wise, your apple tree will need a higher temperature when a seedling, or around 70°F and 75°F. When older, the tree can tolerate a broader temperature set of 65°F and 80°F.
When talking about temperature, we need to discuss lighting. Providing light for most hydroponic plants requires less work than raising it towards the ceiling, but with an apple tree, you will have to consider it.
Most hydroponic specialists growing trees indoors utilize UVB bulb systems or plug the UVB bulb into the ceiling socket. The latter won’t allow for the right lighting conditions for the plant, which will require a solid eight to 12 hours a day of light.
You can purchase an LED grow light to help keep running costs down, but it won’t assist with temperature control.
Apple trees don’t usually grow in humid conditions, so you might need some ventilation in the produce area. This ventilation system doesn’t need to be too complex, as long as there’s some airflow. A simple fan will reduce the risk of mold or fungi growing.
As the tree grows larger, you will need to increase the size of the hydroponic pot. Make sure to prepare for these transplants.
Now that we know the best growing conditions let’s talk about hydroponic setup.
What Type of Hydroponic Setup Do You Need?
Your hydroponic system will have to last, be automated, provide loads of water, and accommodate the size.
Ebb and flow systems are simple in construction and work by flooding the growing chamber at set times. The nutrient solution is allowed to drain away slowly, allowing the roots to breathe.
With most plants, ebb and flow systems allow larger plants to grow to their full potential, but on the scale your tree needs, you’ll have to build your own. Also, these systems aren’t as adaptable as you might need.
Also, your reservoir will have to be very large.
For growing hydroponic trees, a drip irrigation system is best, or in the case of an apple tree, a constant water drip (CWD) method. With drippers, moving the trees around and retransplanting the apple tree is more manageable.
Simply turn off the dripper, move the apple tree, and turn on the nutrient supply. These dripping systems circulate the nutrient solution by allowing the water to drain out the bottom and flow downwards toward the reservoir to be circulated around again.
Check out the best hydroponic systems here: Best Hydroponic Systems - Options for Each Hydroponic Technique
Now that you know that you need to build your CWD system, what are the steps in planting and growing an apple tree hydroponically?
Steps To Growing An Apple Hydroponically
When preparing your CWD, ensure that your grow space can accommodate a tree reaching 6 feet. Deep pots for the dwarf apple tree must adjust between 10.5 and 16 gallons.
For the lighting system, we’d recommend a full-spectrum LED light. Check out our recommendations: Best Hydroponic Grow Lights. When selecting materials for the system, beware that they will need to last as this tree will live happily for 100 years outdoors.
Prepare your rootstock, and pack your growing container with Rockwool and monitor.
As stated, you will want the grow room to be warmer at its earlier stages of life.
When transplanting the tree, never provide a pot too large. Make sure to grow the pot size by three to four gallons at a time.
And use slow-releasing fertilizer. You can use pellets in the growing medium or use a water-soluble nutrient.
For those looking for a challenge, this could be it. We’d strongly recommend not starting this adventure if you’re inexperienced.
It’s also worth mentioning that this is in its infancy regarding developing proper techniques.
Growing An Apple Tree Hydroponically Is Complex
Hydroponically grown apples are very new to the world of horticulture. If you decide to tackle this challenge, you’ll be at the cutting edge of botany research.
It will be in your best interest to sign up for studies with universities or their research newsletters. But we hope this is information to get you started.