The Complete Beginner's Guide to Growing Indoor Plants in Leca
What is Leca?
Leca stands for Lightweight Expanded Clay Aggregate. A fancy way of saying balls of clay that have been baked so they expand (I think of them like clay popcorn, or Aero Bar chocolate). Once they've absorbed water, they expand a little more too, but always retain that super porous texture full of tiny air pockets roots love. Unlike other substrates, they absorb about 30% of their own weight in water, making them a great substrate for plants who dislike being over-watered.
Why grow plants in Leca instead of soil?
Leca is a soil-less medium suited to plants that dislike being over-watered. Leca makes it much easier to 'wet and forget' when watering. There's far less risk of root rot. The chances of pests are significantly reduced too. And it makes checking your plants health super easy. But Leca isn't totally 'wet and forget' - there is some maintenance required, and you have to fertilise - more about set-up, maintenance and Leca-friendly fertiliser all coming up.
Leca = less water worries (and less root rot!)
Plants in Leca essentially water themselves. The clay balls absorb water from the bottom up, yet remain full of oxygen at the same time thanks to all those tiny bubbles of air created when the clay was baked (like an Aero chocolate bar), so roots can take up only what water they need, with less risk of root rot.
That's because root rot is primarily caused by the roots 'drowning' when you water too soon and they can't get enough air, or when you forget to water and root hairs die. Simply keep the water reservoir topped up at the bottom, below root level, and your plant will take what it needs. Done right, you simply can't over-water anymore. Leca absorbs about 30% of its weight in water, with the rest draining away. It becomes your job to simply top up the water reservoir. Leca also extends how long you can go between watering. Very popular for those with lots of plants to reduce maintenance, or those who worry about over-watering.
Leca = fewer pests
You might have read you never get pests with Leca. That's not exactly accurate. But yes, the risk of pests is definitely reduced. Especially pests attracted to rotting organic matter in potting mix, because they won't find what they love in Leca. Fungus Gnats are the major one Leca helps you avoid (helps, not prevents!). Spider Mites love things on the dry side, so they're another one Leca helps keep away because it avoids plants fully drying out.
Leca = better health monitoring
One of my favourite things about Leca is how easy it is to monitor your plant's roots and overall health. There's no hiding with Leca! You'll be able to check those roots every day if you feel the need. It's normal to give in Leca a rinse or clean every fortnight or so, which also means you can give those roots a regular health check at the same time.
Do you have to use Leca by itself?
No, you can (and many people do) use Leca mixed in with potting mix to add drainage, increase oxygen with the added pockets of air, yet also increase even water retention. This guide is more about using Leca by itself for growing semi-hydro.
Is Leca single-use?
Leca is not single-use. Unlike most potting mix ingredients, which decompose and compact over time, meaning it's often thrown out when you repot, Leca is reusable, over and over. Best to boil used Leca between plants to sterilise it.
How do you prepare Leca?
Being made of clay, Leca can start out very dusty! Don't use Leca without prepping it first. Pro tip: Never put plants in very dry Leca, as it wicks water so well it might even suck water out of the roots!
STEP 1: RINSE
When you get your bag of Leca, give it a really thorough rinse until the water runs clear. Best to do this outside so the clay particles just end up in your lawn, not inside where the silt could block your sink! Pro tip: Put Leca in a mesh laundry bag or fish tank media bag and use your garden hose.
STEP 2: SOAK
Once rinsed, soak for 24 hours, just in tap water is fine. The 'Lazy Leca' method is to soak once for 48 hours / 2 days, then pot up. However I prefer to dump out the water from the first soak, and soak in fresh water again for another 24 hours (I prefer the double-soak method, but will sometimes triple-soak too - see below).
Pro tip: You can prep all your Leca in advance. If you won't use up all your prepped Leca right away, all good, just store the rest somewhere cool and dry until needed, and give it a 24 hour soak before use later.
STEP 3: NUTRIENT SOAK (OPTIONAL)
A 3rd soak is optional (so is the second soak really), but for valuable plants, I recommend the triple-soak method for peace of mind. Some always do a triple soak for all plants. For this 3rd soak, ideally use filtered water, or distilled or RO water if you have it. Add hydro nutrients (see below), and soak in nutrient solution for a further 24 hours. Discard the nutrient solution, and you're ready to pot up.
What nutrients do you soak Leca in?
If you do the triple-soak method, the third soak can be in nutrient solution. I use GT CCS root fertiliser, as it has calcium and magnesium included, is free of urea and chlorides (reducing mineral salt build-up for reduced risk of fertiliser burn), and is complete and balanced, formulated for use in hydro and semi-hydro to boost root growth (similar to the popular KLN + Cal/Mag soak popular overseas). Using a root booster or root fertiliser like GT CCS helps roots adjust from water to Leca, or from soil to Leca, with less chance of root melt.
Do you have to boil Leca before use?
You can boil new Leca, but you don't have to. I don't. If you do, I'd do it after the rinse and 2nd soak step. Remember Leca has already been heated to very high temperatures when it was made. However if you are re-using Leca, then yes, do boil it to sterilise it between plants.
How long do you boil Leca for?
After a rinse and 24 hour soak, put the Leca in a pot. Fill water to the same level as the top of the Leca. Boil for at least 10 minutes. Like anytime you use a stove, keep an eye on it during that time. Remove from the heat and let cool. Give a final rinse before use.
Can all plants be grown in Leca?
Like moving from water to soil, and soil to water, if you're moving a plant from soil to Leca, some plants adjust better than others (shifting from water to Leca is the easiest transition). Some plants go through transplant shock, and may lose their roots before they adjust, called 'root melt'. Hardier plants, with faster growing roots, adjust the easiest and fastest to Leca.
What plants are good to grow in Leca?
Plant families often grown in Leca include Monstera, Sansevieria, ZZ Plants, Alocasia, Spider Plants, Syngonium, Orchid and Begonia. In general, plants that do well in Leca tend to share the same characteristics: they like to dry out before watering, tend to grow roots quickly, are hardy enough to cope with being handled often, and prefer airy, oxygen-rich substrates.
What fertiliser should you use with Leca?
Unlike most potting mix, Leca provides no nutrients. It takes care of the watering. You need to provide the nutrients. Some hobbyists buy nutrients separately and create their own mix, or test and add what's needed, however I prefer a simpler method of using an all-in-one hydro fertiliser.
My current go-to is GT Foliage Focus or GT Complete Focus. Both include calcium and magnesium. Both are free of urea and chlorides for less risk of fertiliser and root burn from excess mineral salts. Both are formulated for hydro and semi-hydro. Both are complete and balanced. Another popular all-in-one for hydro is Dyna-Gro Foliage Pro and Dyna-Gro Grow.
Can you use normal fertiliser for Leca?
Leca has different requirements compared to fertilising plants in soil. Because Leca provides none of the nutrients that plants would get from organic matter in potting mix or soil, a complete fertiliser becomes more important. Many fertilisers for indoor plants are not complete. They don't have to be. They are often an 'NPK' fertiliser that provides the main essentials, Nitrogen, Phosphorus and Potassium, but don't necessarily provide all the micro-nutrients. Look for a complete fertiliser that is formulated for hydro and semi-hydro use. GT (Growth Technology) or Dyna-Gro are two well-known brands, both available in NZ, popular for use with Leca.
How much fertiliser do you use for Leca?
I'll normally half the usual dose and add a little fertiliser every time I top up or refresh the water. For GT I use 5mls per 1 litre water. For Dyna-Gro I'd use 1/2ml per 1.5 litres (or 1ml per 3 litres).
What pots are best used for Leca?
Leca is most often used with wick watering or submerged. Wick watering is where Leca absorbs the water through a wick. The wick goes from the Leca into the water reservoir below. Submerged is where the Leca is sitting partially in the water, and pulls water from the bottom to the top.
If you Google 'Leca Pot Setup' and go to Images you'll get lots of ideas for different set-ups and pots you can use for both methods. Leca is a great choice with self-watering pots and wick-watering pots like these. There's no need to buy anything fancy however, a quick Google will show you lots of ideas for DIY Leca set-ups, such as reusing jars or plastic drinking cups. If you do the submerged method, and use a jar or vase, avoid using a vessel that is smaller at the top than the bottom, as you'll likely have trouble removing the plant later without smashing the vessel, or cutting off roots.
For propagation, or for baby plants, or just a really big collection, another popular method is lots of nursery pots (clear nursery pots are popular for this so you can check root development), sitting in seed trays or low-sided clear tubs. The nutrient water is in the tray or tub (this is a method you'll see a lot of Plant-Tubers like Kaylee Ellen use). Either way, you ideally want a method where you can see the water level without having to remove anything to make it easy to know when to top up the water.
How do you transfer a plant from soil to Leca?
STEP 1: Firstly, prep your Leca (see the rinse and soak steps above).
STEP 2: Get cleaning! You need to remove all soil, bark, moss etc from the roots, so roots are completely cleaned of any and all organic matter. I like to give the plant a nutrient bath a couple of days before-hand (see step 1 in 'what to do before you repot') to help the roots handle the cleaning process better and to loosen old, dry potting mix. To remove organic matter, I use anything from a tap to a hose to a fine gentle stream from a squeeze watering bottle, depending on how much pressure is needed and what the plant can handle.
Pro tips: Some roots are easier to do this with than others. Not removing all organic matter (which is harder to do when plants have finer root systems), is a common reason a plant has trouble adjusting from soil to Leca. That's not because of the Leca, but because the remaining organic matter left on the roots sucks up water from the Leca, keeping roots constantly wet, which can cause root rot and eventually root death.
Keep in mind the beauty of Leca is it only holds about 30% of its weight in water. A lot of organic matter in potting mixes hold 2 to 4 times their weight in water, without much space left for air. Root rot often gets blamed on the Leca, when better prep could have avoided it happening. This handy guide by Leca Addict describes ease of transition and tips for each plant family.
Once soil roots adapt to Leca, they will attach and absorb the water they need from the Leca. If you simply can't get all organic matter off the roots, personally I'd consider chopping off that section of root, as the chances of root rot can be so high.
STEP 3: Pot the plant in the Leca. This is much the same as any medium. I only pot into pre-soaked, wet Leca. Never pot in to very dry Leca, as Leca wicks water really well. If the only water available is in the roots, it could suck water out of the roots, instead of the other way around.
Pro tips: Pot up so roots are well spread out instead of clumped together, touching each other. In case you get root rot during the transition, it is less likely to spread if the roots aren't touching. You can trim long roots that will otherwise get tangled together. Trim back only what the plant can handle to lose (this depends on the plant. a ZZ for example can lose a good third or more of its root mass without any major issues).
STEP 4: Add water to the reservoir with your choice of nutrients. The water level should be about 1/4 to 1/3rd of the way up if you're doing the submerged method (not wick method). I like using GT CCS for the first 4 to 6 weeks as it's a root fertiliser that's also complete and balanced, formulated for both hydro and semi-hydro (Leca is semi-hydro). A root fertiliser helps damaged roots recover faster, and helps initiate new root growth sooner. I then shift to a complete hydro fertiliser like GT Foliage Focus once water roots start to appear. Some add seaweed also (which also helps reduce transplant shock). There are lots of nutrient options.
WEEKLY FLUSH (Optional): You can give a newly transitioned plant regular flush or wash in the shower or running water once a week during the first 3 to 4 weeks if you couldn't remove all organic matter during prep, or if the plant looks like it's having trouble adjusting.
Maintenance for growing in Leca
The first month in Leca
When shifting a plant from potting mix to Leca, soil roots need to transition into water roots. The first month or so is the time to keep a really close eye on how your plant is adjusting. There are a few ways to help those roots adjust. One method I use is to start off with a higher-than-normal water level. I put the water level about 1/3rd of the way up the Leca temporarily.
I use either GT CCS which is a root fertiliser, or add a little seaweed also (I use the BioPower Seaweed). I've also tried seaweed only by itself for the first couple of weeks, and only added GT CCS once the first water roots appear.
Either way, once those lovely white water roots have appeared, and the plant's doing well, you can maintain that higher water level (remember roots that have grown down into the water will have adjusted to growing fully submerged) or you can reduce the water level to about 1/4 so it stays below the roots, or shift to wick watering.
Some plants simply don't transition well from potting mix to Leca. For those I transition from water to Leca instead, which is much easier as the plant already has water roots. I take a cutting and propagate in water then shift to Leca.
After the first month
Once your plant's settled in and doing great, maintenance for Leca is minimal. A flush water or flush shower about monthly is usually all that's needed, as well as topping up with nutrient water when needed in-between flushes.
I add a hydro fertiliser at half strength every time I top up the water. You can also use it full strength fortnightly or monthly, and just top up with plain water in-between.
Both the quality of your water and your chosen fertiliser play a big part on how often you need to flush your Leca. Hard water will build-up minerals faster than filter water or distilled water. A better quality fertiliser made for Leca is less likely have excess mineral salts build-up as quickly as a lower quality fertiliser.
If you do see a white or salt-like residue building up on the Leca, this is most likely excess minerals from your water or fertiliser (or both), and you might like to either improve the source, or flush more often than monthly (or both). If all is well, about once a month, dump out your old water entirely. Give the Leca a good flush. Make up fresh nutrient water, and top it back up.
How to flush Leca
To flush Leca for the submerged method, where your container doesn't have drainage holes, simply run water into the container for a few minutes, letting it overflow, or take the container into the shower and let it run into the pot (plant and all) for a good 5 to 10 minutes. If doing this in the sink, and you don't want to leave the tap running, completely fill and tip out the water, three times over. Once done, tip out the water, and refill with nutrient water. It's fine to use tap water to flush your Leca as it won't be staying in the pot for long.
To flush Leca for the wick watering method, remove your inner pot from the outer pot, empty out the water from the outer pot. Under the tap or shower, rinse the Leca in the inner pot thoroughly for a few minutes. Let the excess drain, then return to the outer pot with fresh nutrient water.
Trouble shooting & problem solving for Leca
How do you treat root rot in Leca?
If you're seeing signs of root rot, add Hydrogen Peroxide to the water. If you can see organic matter still suck to roots, do a flush to get rid of as much of it as possible (you can also gently pull off any rotted roots at the same time). You don't want rotting roots in contact with healthy roots.
I use Oxygen Plus 3% For Plants as a wash, soak or in the water reservoir, depending on how bad the rot is. Oxygen Plus is 3% Hydrogen Peroxide mixed with distilled water. If caught in time, there is hope. H202 (the chemical symbol for Hydrogen Peroxide), kills the bacteria and fungi responsible for root rot, and restores oxygen to help remaining roots recover faster.
Directions: 5mls of Oxygen Plus 3% per 1 litre of water added to the water reservoir, or a soak or flush in a 1:1 ratio of Oxy Plus and water.
How do you get rid of algae with Leca?
Leca is very popular used in clear pots and containers as it's so easy to see both the roots and the water level, however that also makes it a lovely environment for algae to grow. Algae loves warmth and light. In small amounts algae is not likely to cause any issues, but it doesn't look great.
A clear inner pot - so you can check roots - combined with an opaque outer pot (so you don't get algae), is an ideal set-up to avoid algae. If you prefer clear, like growing in a glass jar or vase, remember algae is a plant, so products that kill algae might also harm your plants.
One treatment that won't harm roots but will kill algae is Hydrogen Peroxide. I use the Oxygen Plus 3% For Plants brand at 3mls per 1 litre water.
How do you treat Fungus Gnats in Leca?
Although far less likely in Leca than in potting mix, the common belief that Leca means no Fungus Gnats is a myth. In case you do get them, sprinkle a few granules (half a teaspoon or less) of Mozzie Bits in the water once a week until they've gone (the granules slowly release a natural bacteria that kills the larvae but won't harm you or your plants). Fish out used granules weekly. You can also prepare Mozzie Tea, add your fertiliser like normal, and use mozzie tea for a few weeks until gone.
How do you treat Spider Mites or Mealy Bugs in Leca?
I find there's really no difference in how you treat Spider Mites or Mealy Bug for plants in Leca, since the treatment focuses on the leaves more than the roots, however I do find bugs in general much easier to treat in Leca. One method that works great is an insect dip. Choose your treatment of choice, and instead of spraying it on, you can just drench or dip the entire plant in it, upside down and all. Try that with a plant in potting mix!
Do you need to repot often with Leca?
Well, no, not really. If anything, I repot less often with Leca. Leca doesn't compact or decompose like potting mix, so you don't need to replace it every few years like you do potting mix. Some people pot up every few weeks! I don't think it's needed, plus disrupting the roots that often isn't ideal for the plant either. Some repot because the roots have grown down into the water reservoir. If the roots have grown in to water, they will have adapted to living in water, it doesn't mean you need to pot up so the water is always kept below the root level.
Is tap water okay to use for Leca?
I would stay away from tap water for Leca. It's not that it's not possible, it just makes it more difficult to give your plants correct levels of nutrients, and to avoid both deficiencies and excess, because rain water and tap water include minerals, but so does your hydro fertiliser. The risk of mineral burn goes up.
One solution is distilled water. 10 litres of distilled water usually costs under $10 from the supermarket. Distilled water will have no flouride, no heavy metals, no chlorine and will be pH neutral. Some hydro fertilisers are pH buffered to bring the water to an ideal pH for plants and nutrient uptake (GT is a pH buffered fertiliser). You can leave tap water out overnight, which will mean the chlorine will evaporate, but you can't remove the flouride, even with a filter. RO water or distilled water are the options I'd look at for Leca.
What are the downsides of Leca?
The cost and the prep are the main downsides of Leca. After that, Leca has more pro's than con's in my opinion. But it doesn't suit everyone. I have far more plants in potting mix than Leca. Some plants simply don't transition well from potting mix to Leca, although even those often do great shifting from water to Leca. Set-up is obviously a bit of a chore. A lot of rinsing and soaking, both for the Leca and the plant. You don't want to pinch pennies on fertiliser either. Get the good stuff. However I feed my potting mix plants the same quality anyway.
My suggestion is to take it easy and have fun with it. Don't spend too much. Just get a small bag of Leca, and try a DIY pot. Start with only one plant. Try starting from a water rooted cutting and pot up in to Leca. Or start with a really hardy plant with fast growing roots, like a Monstera or ZZ plant. Pick a lower cost plant just in case your learning curve is a bit hit and miss at first.