Introduction to hydroponics, part 1
Have you ever heard of hydroponics? If not, you are in the right place. In this article, we introduce hydroponics at home and show you how to switch houseplants that you grow in regular potting mix in a planter over to hydroponic growing.
What is hydroponics
Hydroponics is a modern way of growing plants, and you will surely appreciate that it works for herbs, fruit and vegetables too. On top of that, it is a very clean way of growing. For hydroponic growing, you do not need any soil or “potting mix”. Hydroponics can be used in several ways. We will focus on the home method, the very simplest one, which you can set up yourself at home. There are, of course, also hydroponic systems that you can see in shopping centers or office buildings, whether in large containers or in green walls, which use electricity and special growing formats where water circulates and gives the plants everything they need.
How does hydroponics work?
Nothing could be simpler than hydroponic growing. For many people who struggle to grow houseplants and often end up giving up on the plants in their home, hydroponics is a way to make growing fun and, on top of that, practically carefree.
Compared with classic growing in potting mix, hydroponic growing does away with one key thing: watering. Or rather, of course you still have to water, but a little differently. With regular growing, you have to keep checking the moisture of the potting mix, and it can easily happen that you overwater a plant or, on the contrary, let it dry out. Every summer you have to figure out what will happen to your plants while you are on vacation, among other headaches. Not to mention that hydroponics is much less attractive to pests.
The solution? Hydroponics. The beauty of it is that all you need is water, a growing medium (for example expanded clay), a plant and, of course, a suitable pot cover and a grow pot with a water level indicator. In hydroponics, the plant draws nutrients only from the water, helped by the permeable growing medium, which absorbs moisture and water. In a relatively short time, a clean root system forms and takes the nutrients it needs to grow from the medium. In hydroponics, it is important to keep the right water level in the planter, as too much water can cause root rot. A water level indicator helps a lot here: it shows you the low, optimal and maximum water level.
What do you need for hydroponics, and why?
At home, you need only very few things for hydroponics compared with classic growing:
1) A plant
If you decide to try switching a plant that has been growing in potting mix to hydroponics, think carefully about which plant, because the switch to hydroponics is never 100% certain and the plant may die. Plants that root well in water are good candidates for a more successful switch. Less suitable, on the other hand, are plants that generally do not root very well, or plants with very fine roots, which are more prone to rot. It is also not a good idea at all to transplant large, mature plants or shrubs. The bigger the plant, the riskier it is to handle its root system. If you want to try a plant in hydroponics for the first time, consider plants from the aroid group, except alocasias, which are more demanding to grow. Especially good choices include Epipremnum or Scindapsus and Syngonium, which root very quickly, so there is a good chance you will not kill the plant if you want to convert a potted plant rather than start from cuttings already rooted in water.
2) A growing medium.
You can use the most widely available one, expanded clay (LECA). But other growing media work too: Seramis, zeolite, Managreen or perlite on its own. All these media are highly porous and permeable: they soak up water and retain moisture. This creates a suitable, very moist environment in which the plant’s roots thrive.
3) A watertight planter
Since the plant has to stand partly in water, you need a completely watertight planter that does not leak and cannot let water seep out. So when choosing a suitable planter, first test whether it is really waterproof.
4) Grow pots with holes and a water level indicator
If you want to go the hydro route with as little hassle as possible, you will also need a grow pot to go inside the planter. It has holes made specifically for this purpose that let water flow through, and an opening for a water level indicator that fits the pot exactly. If you do not use a grow pot, maintenance will be considerably more complicated. Not only does the pot hold the plant together with the medium, you can also swap the decorative planter for another one at any time without having to take out the whole plant and go through a complicated move. It is also useful for occasional maintenance of the plant, when you need good flow through the pot from top to bottom. The water level indicator (water gauge) in the pot helps you keep the optimal amount of water in the planter. The wrong amount of water can cause trouble for your plant.
Does the plant live on water alone?
No. Even in hydroponics, plants need suitable nutrients. Unlike regular growing, hydroponics uses special nutrient solutions designed specifically for hydroponic growing, although they cost a bit more than regular fertilizers. If you want to use regular fertilizers, you will need to focus primarily on water-soluble mineral fertilizers and keep a closer eye on the amount, as even fertilizers for plants without potting mix can burn the roots, which would then start to rot. If you like using lignohumate, which is otherwise good for roots, use it very carefully in hydroponics as well, because a larger amount of lignohumate can also cause root rot very quickly. You can also reach for a loose granular fertilizer for hydroponics, which you mix with the growing medium, and the roots will absorb the nutrients gradually.
What should you watch out for in hydroponics?
Hydroponic growing is not foolproof either, and there are a few things to watch out for. The most important thing, however, is to follow these basic rules so that your plant does as well as possible.
1) Sunlight may be good for some houseplants, but if you grow them hydroponically, keep in mind that the plant is no longer in potting mix but in water. Direct sunlight can therefore cause green algae to grow if the medium is in a transparent container, and it will make the water evaporate much faster. Green algae not only harm the plant’s roots and take away their oxygen, but also very quickly foul the growing medium, and the plant starts to struggle. So think about where you place the plant and about a cover for the grow pot.
2) The water should ideally be left to stand. Water straight from the tap is too hard and contains minerals and chlorine, which is not suitable for growing plants. Let the water stand first so that the unwanted substances dissipate. Watering with water that is too hard leaves a white to crystalline crust on the growing medium as substances precipitate on the surface, and too thick a layer can harm the lower leaves and the roots, on which even limescale can form.
3) Roots. It is a good idea to rinse the plant with clean water about 1 to 2 times a month to flush waste substances and bits of decaying roots out of the medium. This keeps the growing medium clean.
How to switch a plant to hydroponics
There are basically 2 ways. The first is rooting cuttings of the plant and waiting until the new root is a few centimeters long. That is because we need the root to reach deeper into the medium and not be completely submerged in water. The second way is to convert the plant to hydroponics, and that is the method we will look at in more detail in this article.
Photo: First remove the excess potting mix from the plant, then scrub and clean off as much of the remaining potting mix as you can under running water. A soft toothbrush can help.
Step 1: Preparation
Choose a suitable plant. In this article, we used Syngonium Dark Maria. You will also need a soft toothbrush and possibly potassium permanganate crystals, which you can buy at a pharmacy. Take the plant out of its planter and scrub all the potting mix off the roots. When you feel you cannot get any more off, gently massage the roots with your fingers under running water and try to remove as much of the remaining soil as possible. Do not worry about damaging the roots. Many bits of root will fall or break off, but nothing terrible will happen; just make sure that each stem of the plant has its own root. When your fingers cannot do any more, you can use a very soft toothbrush and gently clean the roots under water. When you are done, rinse the plant thoroughly and check it for pests. Put the plant with its almost clean roots in clean water (in a vase or another container) for about 7 to 14 days and give it time. Why potassium permanganate? Potassium permanganate is a purple crystalline substance that acts on the roots as a natural disinfectant against possible rot or infection, which could cause mold on the roots in water. Only a small amount is needed, and the roots only need to stay in it for a few hours. Then you need to change the water so that the roots do not get burned. In 99% of cases, though, you can manage without potassium permanganate.
Photo: Get everything shown below ready, and you can start.
Step 2: Let’s get to it
After about 14 days: prepare the growing medium, in our case expanded clay. To start with, we recommend using the smallest 12/13 cm grow pot with a water level indicator. For this grow pot, exactly 1 L of expanded clay will be enough. The plant you have been keeping in clean water has probably already started growing new, so-called “water” roots, which take hold in a hydroponic environment much better and faster. First, rinse the expanded clay or other medium thoroughly. You can also pour boiling water over it from a kettle or pot to “boil” the medium. You need to wash away the dust and dirt and, at the same time, let the medium soak up water so that it is not dry. If you decide to use a granular fertilizer, mix it with the wet medium in a bowl beforehand.
Photo: Pour the cleaned expanded clay into the bottom of the grow pot up to about the top of the holes in the pot, put the plant in and fill it up to the rim.
Step 3: Potting the plant in the grow pot
Pour the required amount of expanded clay into the hydroponic grow pot, ideally up to the height where the bottom holes for water flow end. Then take the plant, spread the roots over the whole area of the pot and gradually cover the plant with expanded clay from all sides. Do not pack the expanded clay down too firmly, or you may tear the roots. It is important that the plant sits firmly in the pot and cannot wobble. The roots should be neither completely submerged in water nor too high. Once the pot is filled to the rim, all you have to do is insert the water level indicator into the opening in the pot, rinse the whole plant with water and put it into the watertight planter. The last step is topping up the water. The mark on the water level indicator shows you how much water you need to add. The middle mark is optimal. The bottom mark means it is time to add water. Fill up to the top mark only if you are going away for a longer time. If you add more water than the top mark shows, you will most likely cause the roots to start rotting.
And that’s it. Easy, right?
In part 2 of this article, we take a closer look at plant care in hydroponics and the options hydroponics offers.
Author: Martin Seidl