Leca / Semi-Hydro Guide

Leca / Semi-Hydro Guide

I put off trying Leca for two years because it seemed complicated. Everyone online made it sound like you needed a chemistry degree just to keep a pothos alive. Spoiler: you don’t. After converting about fifteen of my plants over the past year, I can tell you it’s actually pretty forgiving once you understand the basics.

Leca stands for Lightweight Expanded Clay Aggregate. They’re little clay balls that you use instead of soil. The setup is called semi-hydroponics because the roots sit partially in water and partially in air. It’s different from full hydroponics where roots dangle directly in water, and it’s definitely different from soil where everything is mixed together.

I’m going to walk you through exactly how I do it, what worked for me, and what didn’t. This isn’t the only way to use Leca, but it’s what I’ve figured out through trial and error in my own apartment.

Transitioning soil to Leca

The first time I moved a plant from soil to Leca, I was so nervous I almost talked myself out of it. I picked a golden pothos cutting because I figured if I killed it, at least pothos are easy to replace. Turns out, the transition is the trickiest part of the whole process.

Start by taking your plant out of its pot and removing as much soil as possible. I do this in my bathtub because it gets messy. Hold the plant gently and shake off the loose dirt, then run lukewarm water over the roots to rinse away the rest. You want the roots as clean as you can get them without being rough. Some people soak the roots in water for a few hours to make the soil easier to remove. I’ve done this both ways and honestly can’t tell much difference.

Here’s the thing nobody tells you: your plant will probably look sad for a few weeks. The roots that grew in soil are designed for soil. They have tiny root hairs that grab onto soil particles. In Leca, those root hairs don’t work the same way, so the plant has to grow new roots that are better suited for a water environment. This is called the transition period, and it can take anywhere from two weeks to two months depending on the plant.

During this time, I keep the water level higher than I normally would. Some people keep the water touching the bottom of the roots, others submerge the roots about halfway. I split the difference and keep it about a quarter of the way up the pot. The plant needs easy access to water while it’s growing those new roots.

I’ve had the best luck transitioning plants in spring and summer when they’re actively growing. I tried moving a monstera in January once and it just sat there looking miserable for three months. Growth season matters.

Young plants and cuttings transition way easier than mature plants. If you’re just starting out, I’d suggest either buying a small plant specifically for this or rooting a cutting directly in Leca. I’ve rooted probably twenty pothos and philodendron cuttings straight into Leca without any transition drama at all.

Nutrient water explained

This is where people get intimidated, but it’s really not that deep. In soil, plants get nutrients from organic matter breaking down. In Leca, there’s nothing to break down. The clay balls are inert. So you have to add nutrients to the water yourself.

You need a fertilizer designed for hydroponics. Regular plant fertilizer can work, but hydroponic fertilizer has a better balance of micronutrients. I use General Hydroponics MaxiGro because one bag lasts forever and it’s not expensive. There are fancier options, but this works fine for my philodendrons and pothos.

The mixing ratio is important. I use about one-quarter to one-half of the recommended strength on the fertilizer package. Full strength is way too much and will burn the roots. I learned this the hard way with a pearl and jade pothos that got crispy brown tips. The research I’ve done suggests that most houseplants do better with a weaker, more consistent feeding rather than occasional strong doses.

I mix up a big batch of nutrient water in a gallon jug and use it to refill my Leca pots over the course of a week or two. Some people mix it fresh every time. I’m lazy and haven’t noticed any problems with my method, but if you want to be precise about it, fresh is probably better.

The EC (electrical conductivity) and pH levels are things that serious growers measure, but I don’t own the meters and my plants are doing okay. If you want to get technical about it, most houseplants like a pH between 5.5 and 6.5 and an EC around 1.0 to 1.5. Universities that study hydroponics recommend these ranges, but again, I’ve gotten by without measuring.

One thing I do pay attention to is the water level. You don’t want the water touching the base of the plant stem. That can cause rot. I keep the water level in the bottom third of the pot and let it dry out almost completely before refilling. The Leca stays damp even when the reservoir is empty, and the roots grow down toward the water.

Above: A close up look at the symptoms.

Flushing the system

This is the maintenance part that nobody warns you about upfront. Mineral salts from the fertilizer build up in the Leca over time. You’ll notice a white crusty layer forming on the clay balls or around the rim of the pot. That’s your sign that it’s time to flush.

I flush my plants about once a month. All that means is running plain water through the pot to wash away the built-up salts. I take the plant to the sink, pour water over the top, and let it drain out the bottom. I do this a few times until the water runs clear. Then I dump out any remaining water in the reservoir and refill with fresh nutrient solution.

Some people do this every two weeks. Some wait longer. It depends on how much fertilizer you’re using and how fast your plant is drinking. The University of Florida’s horticulture extension recommends regular flushing for any hydroponic system to prevent toxic buildup, and I’ve found it makes a real difference in how healthy my plants look.

If you skip flushing for too long, you’ll start seeing brown leaf tips, yellowing, or stunted growth. I ignored my calathea for about six weeks once and it started throwing a fit. Two good flushes later and it perked back up.

You can also take the plant completely out of the pot and rinse the Leca itself. I do this every few months, especially if I see algae growing on the balls. Algae isn’t necessarily bad for the plant, but it looks gross and can make the whole setup smell swampy.

Pros and Cons of Leca

Let me be honest about what I actually like and don’t like after using this setup for a year.

The biggest advantage is that I can see the roots. In soil, you’re guessing. In Leca, if you use a clear plastic nursery pot inside a decorative cache pot, you can literally watch the roots grow. This is incredibly helpful for diagnosing problems. Root rot looks different than healthy roots. You can see if the plant is growing new roots or if something is wrong.

Pests are way less of an issue. I haven’t seen a fungus gnat since I switched my plants over. Thrips and spider mites can still show up, but soil pests are basically eliminated. That alone might be worth it if you’ve ever dealt with a fungus gnat infestation.

Watering is more predictable. Once you get the hang of it, you just refill when the reservoir is empty. There’s no guessing about whether the middle of the soil is still wet or sticking your finger in to check moisture.

The cons are real though. The upfront cost is higher. Leca isn’t expensive, but you need enough to fill your pots, plus fertilizer, plus the pots themselves. I spent about sixty dollars getting started with supplies for five plants.

The transition period can be brutal. I’ve lost two plants during the switch. One was a string of pearls that just gave up entirely, and the other was a calathea that was probably doomed anyway. If you have a plant you really love, maybe don’t experiment on that one first.

It’s less forgiving if you travel. In soil, most plants can handle a week or two of neglect. In Leca, if the reservoir runs dry and you’re gone for ten days, things can go downhill fast. I’ve had to recruit my neighbor to check my plants when I visit my parents.

Also, it’s not great for every type of plant. I haven’t figured out how to make it work for succulents, and I’ve read that plants with very fine roots sometimes struggle. According to research from hobbyist growers, aroids like pothos, philodendron, and monstera do really well. Calatheas are hit or miss for me.

Above: The tools you need to fix this.

Setting up the pot

The actual setup is simpler than the internet makes it sound. You need three things: a pot with drainage holes, Leca, and a cache pot or saucer to catch the water reservoir.

I use clear plastic nursery pots for the inner pot because I like seeing the roots. You can use terracotta or ceramic if you drill drainage holes in the bottom, but then you can’t see what’s happening inside. The outer pot can be anything that holds water. I use basic ceramic cache pots from the hardware store.

Rinse your Leca before the first use. Straight out of the bag, it’s dusty and has a lot of fine particles that will cloud your water. I put the Leca in a colander and run water over it until the water runs clear. Some people soak it overnight. Either way works.

Put about an inch or two of Leca in the bottom of the inner pot. Hold your plant in place and fill in around the roots with more Leca. You want the roots surrounded but not packed in tight. The clay balls should be loose enough that air can flow through. I usually fill the pot to about an inch below the rim.

Set the inner pot inside the cache pot and add your nutrient water. Pour it slowly until you can see the water level in the bottom of the cache pot. You want about one to two inches of standing water. The inner pot sits in this reservoir, and the Leca wicks the water up to the roots.

That’s it. That’s the whole setup. The plant sits there and does its thing. You check every few days to see if the reservoir needs refilling, and once a month you flush the system.

I wish someone had explained it this plainly when I started. It’s not magic, and it’s not rocket science. It’s just a different way of growing plants that works better for some situations and some people. For me, it’s been worth the learning curve, even with the couple of plants I lost along the way.

References

University of Florida IFAS Extension. “Fertilizer Management in Hydroponic Systems.” Accessed through their horticulture department publications.

General Hydroponics. Product guidelines and feeding schedules for MaxiGro fertilizer.

Various semi-hydroponics grower communities and forums documenting transition methods and troubleshooting, including experienced hobbyist accounts of species-specific successes and failures with Leca systems.