Hydroponic Lemon Tree

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By Jeff Hale

Growing trees in a hydroponic system is a tricky project to undertake. But out of all the fruit-bearing trees, growing lemon trees are arguably the easiest.

This is because the lemon trees, and other citrus trees, have relatively easy roots to manage. Also, they are readily available from garden centers as dwarf trees, which are created to be smaller in structure.

As with all plants grown hydroponically, you will need to replace the soil with a nutrient solution that balances all their nutritional needs.

Growing plants hydroponically does normally mean you’re saving space, conserving water usage, being more efficient with nutrients, and protecting plants from soil-borne diseases. But when the plant you’re growing is a tree, these beneficial elements (except the soil-borne diseases) are not as substantial as with other plants like vegetables.

And the fact is citrus trees require lots of water, sun, and root space – no matter if they’re dwarf versions or not.

But growing citrus trees hydroponically is one of the best projects for a keen horticulturist, so it’s worth putting up with the extra work.

Now, let’s investigate the perfect growing conditions you’ll need to mimic when growing hydroponic lemons.

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Perfect Hydroponic Growing Conditions For Lemon Trees

Lemon trees are considered a generally low-maintenance plant, and certain varieties can live in the home during harsh winters.

Citrus trees as a whole love sunlight and will lap up 6 to 8 hours of direct light and more a day. And when potting them outdoors, it is best to do it during early spring to avoid the harsh conditions of winter and summer.

But with hydroponics, you will most likely be growing them in a large indoor space. A generalization with citrus trees is they don’t like having their roots sitting in water and will require good drainage.

The climate you want to mimic is tropical to semi-tropical climates, like those in the USA citrus belt in California and from the Gulf Coast to Florida.

You can grow lemons in colder conditions, but for your hydroponic setup, the key to a large crop is to recreate the perfect environment. Lemon trees are happy between temperatures of 75°F to 85°F.

And as you can imagine, they love a little humidity, so try to get as close to 50% as possible.

Lemon trees are hungry, fruit-bearing plants. They will require a constant supply of nutrients in your system, with a complete NPK (nitrogen, phosphorus, potassium) fertilizer. And if they are struggling to produce fruit, a top-up with Epsom salts will help immensely.

Be aware that citrus trees do have sensitive roots. This means adding too much of a nutrient mix to the solution might cause a decrease in access to oxygen in the system. To ensure that the nutrients are balanced, you will need to conduct pH and electrical conductivity (EC) testing, regularly.

Your pH should be around the standard 5.5 to 6.5. Citrus trees are not salt tolerant so when testing EC levels, ensure the readings are below 2,200ppm. This will require flushing the system when levels exceed optimal intensity.

When growing hydroponic lemon trees, the variety can make a large difference. Let’s have a look at some of them.

Different Lemons Trees You Can Grow

There are roughly 30 varieties of lemon trees in the world. Each of these varietals will have certain unique characteristics. Some of these trees will handle the cold better and be smaller in size.

The small size of some of these trees puts them in the top selection for hydroponics.

Lisbon Lemon

One of the most popular lemon trees in the world, these produce the fruit you can buy on the shelf. As a tree, it can tolerate huge swings in temperature and will produce fruit non-stop after its first successful crop.

These can also be made into dwarf trees.

Meyer Lemon

While the fruit of a Meyer lemon tree will be smaller than those on a Lisbon tree, they produce a delicious fruit which is a crossbreed between a sour lemon and a sweet orange, making them popular.

Meyer lemon trees require little space to grow and can be happily grown indoors. And due to their smaller size, they require less water and nutrients, a bonus if you’re growing an indoor crop.

While the Meyer lemon is ready for indoor hydroponic growing, the Lisbon lemon will need to be grown from a dwarf version of itself.

But what is involved in creating a dwarf lemon tree?

Creating a Dwarf Lemon Tree

Lemon trees are perfect candidates for creating dwarf versions of themselves. You can even grow citrus trees from their own cuttings. To root a branch, you need to snip off a branch that is not brand new or too old and established; the best are green, semi-established branches. If it is hyper-flexible, it’s too young; if it snaps, it’s too old.

Cut the branch off and remove the lower leaves. Then place it into a small pot with potting soil with fertilizer, and watch it root. Make sure to put your cuttings in a sunny window.

While purchasing a small lemon tree from a garden center isn’t too much of a challenge, you can also create your own dwarf tree through grafting, which is when you join a cutting (also known as a scion, to rootstock that suits your growing needs.

When mating the rootstock with the scion, you will be blending two different plants with distinct properties. Your rootstock could be excellent for handling colder conditions, while the scion promises to deliver a specific type of fruit.

Grafting takes time to master, and you should expect to fail a few times.

With rooting cuttings or grafting, you will shorten the waiting time for your first fruit. If grown from seed, the tree can take up to 5 years to produce, and the result is not guaranteed.

Now that we’ve covered the basics, let’s talk about what hydroponic system you’ll require.

Hydroponic Requirements for Lemon Trees

When growing lemon trees, most will suggest selecting between a deep water culture (DWC) system or drip irrigation. We’d suggest selecting the drip irrigation system, although others would suggest going with the DWC.

We believe using drip irrigation allows for more flexibility regarding pot size. Also, when it is time to move the trees, it is simpler to do so with a dripper system. Just wheel in a trolly, move the tree, and place the dripper back in place.

A major consideration is also the height of the grow light. With all trees grown hydroponically, the height and size will dictate where and how you install the grow light. If you’re growing trees you’ll need to adjust the grow light throughout the early stages of growth.

The next factor to consider with lemons is they require a lot of sunlight.

Choosing a hydroponic full-spectrum LED light will assist with this. Also, it will help with power bills. Your lemon tree will require at least six to eight hours of sunlight daily, with the optimum level being 12 hours.

Your growing medium will likely be a coco coir substrate, but smaller trees can be rooted in Rockwool. You can vary these growing mediums between stone wool or rice husks, but as long as it allows for good drainage, you should be good.

The constant flow of water can often bring down the temperature in a grow room. For this reason, you might want to invest in a small aquarium heater to ensure the temperature doesn’t drop too low.

Now it’s time to walk through the process of setting up your hydroponic setup.

How To Assemble Your Lemon Tree Hydroponic System

As we mentioned, most will suggest using a DWC system to grow a lemon tree, but the margin for error is more significant with DWC when compared to a more straightforward drip irrigation system.

With a drip irrigation system, you will connect the drippers to the water source, dripping the nutrient solution at the tree’s base. And you can always add more drippers if required.

The potting medium should allow quick drainage through the substrate into a catchment area that will flow back into the main reservoir.

Set the water timings at five to eight times a day, with watering intervals of 10 minutes.

Harvesting is a simple process of picking the fruit straight off the tree. You can leave the fruit on the tree for months, keeping them fresh. But the longer you wait, the longer it takes for the next flowering cycle to occur.

And to ensure the fruit does develop, you will need to hand pollinate the flowers on the trees. A paint brush will do to transfer the pollen from flower to flower.

Now You Know How Grow Lemons Hydroponically

Growing a tree hydroponically will mean spending more than usual on your initial setup. You will need more water, fertilizer, space, light, growing medium, and more parts for the system. But we think it’s worth it for the fruit!

But you get it right; you could harvest a crop of oranges all year round. For those lusting for that zesty citrus aroma and fresh is a must, then growing your lemons in a hydroponic system is worth it.