The Ultimate Guide to Growing Indoor Plants in Pon [Lechuza Pon]
The first time I heard about Pon was from Kaylee Ellen (from The Rare Plant Shop in the UK and YouTube fame). Leca and Pon are the so-called 'secret' to how a lot of collectors with a huge indoor jungle can manage to care for hundreds (or in Kayle Ellen's case, thousands), of indoor plants without quitting their day jobs just to keep up with watering - and without over-watering and losing everyone to root rot. Easy peasy.
So of course with my own indoor plant numbers growing (pun totally intended), I had to find out what all the fuss was about. The first time I tried Pon was for propagation. I had some stubborn, hard-to-root Hoya that weren't rooting, even in my usual magic combo of fern fibre and CCS rooting formula. Changed to Pon and they took off. Let's find out what this 'secret substrate' is all about, the pros and cons, and what to consider before you try it for your indoor jungle...
What is Pon?
The best-known brand of Pon is undoubtedly Lechuza, but Pon is what's in the bag, which gets its name from 'Semi Hydro-PON-ics'. It's a popular 'remedy' for fungus gnats, just like Leca, but tends to be more user friendly than Leca for growing and propagating, and is used both added to potting mix, as well as by itself.
Pon is a soil-alternative. It looks like small stones or gravel. Although there are small variations between brands, Lechuza Pon is the 'gold standard' and their ingredients for Pon are pumice, zeolites, lava rock and a little short-term slow-release fertiliser boost (note the short-term bit, more about why that matters coming up).
Lechuza Pon has the 'magic ratio' of 45% water and 55% air. I can almost hear my aroids and hoya breathing a sigh of relief at that, what with their love of chunky, free-draining substrate (and my fear of over-watering). And yes, aroids and hoya are the most popular Pon plants, but Pon is also popular for Bonsai cacti, succulents and more.
What are zeolites?
Pumice (also called Bims), lava rock and fertiliser probably didn't make you blink an eye. But zeolites? That one was new to me. Zeolites are natural volcanic minerals. These clever little crystal-like stones trap harmful heavy metals and pollutants like lead and nickel. They have high water storage, soaking up excess water to keep the mix airy, releasing water when the roots need it. Zeolites also have a natural fungal inhibiting effect and help balance the pH.
What are lava rocks?
These I had heard of, and they are pretty much what they sound like. Lava rocks are scoria, a type of volcanic rock. Super porous, so full of tiny holes which absorb excess water and nutrients, helping avoid root rot from overwatering and holding on to nutrients until roots need them. Often used as a bottom layer in terrariums and pots without drainage. Scoria or lava rocks are a common addition to bonsai, succulent and cacti mixes.
Do you still need to fertilise when using Pon?
Yes! This is the bit I mentioned earlier about the fertiliser in Lechuza-Pon. Some Lechuza substitutes don't include fertiliser (which isn't a bad thing), but because Lechuza-Pon does include a short-term, slow-release fertiliser, although you do not have to fertilise right away, you DO still need to fertilise long-term.
I personally fertilise anyway, but the one I use is a specialist root fertiliser to help plants adjust after repotting and really get that root growth humming, is formulated for semi-hydroponics and is free of both urea and chlorides to avoid fertiliser burn. I just use it at half the dose.
If you don't have something quite that fancy-pants in your plant cupboard, I would skip the fertiliser for one season (about 3 months) after upgrading to Pon, then start with the 'weakly weeky' method after that (diluting your fertiliser and using 'little and often' every time you water).
If you've transferred to Pon in winter, or at a cooler time of year, the slow-release fertiliser will break down more slowly, so you are better to skip the fertiliser for at least 2 seasons (about 6 months) instead before returning to your usual fertiliser routine.
Can you mix Pon in with potting mix?
Yes, Pon's a very popular additive to potting mixes for plants that like things airy and free-draining. There are 3 mains ways hobbyists use Pon. The 25%, 50% or 100% method.
The 25% method is when people use Pon for drainage only, usually in vessels without drainage holes like terrariums, adding a layer of Pon to the bottom quarter or so of the pot, and the rest on top being your usual potting mix.
The 50% method is a protective Pon layer, with the bottom quarter or so inside the pot, filling in the outside edges, and finishing with a top layer of Pon on the surface to help avoid pests such as fungus gnats, keeping your usual potting mix covered, in the middle around the roots. This method is popular if you're using Pon for it's pest resistant properties (keep in mind that doesn't include all pests, and Pon isn't an insecticide, but more about pests coming up).
The third method is a complete repot into 100% Pon. That involves removing all organic matter like soil and potting mix, rinsing the roots, then planting fully in Pon. This is also popular for avoiding pests (mainly fungus gnats, but more about pests coming up). 100% Pon also helps avoid irritants for sensitive or allergy sufferers such as fungus spores.
The other way Pon can be used is just mixed evenly in to soil or potting mix to make it heavier, airier and more free draining.
What are the differences between Pon and Leca?
Pon tends to be much smaller, like small gravel (it reminds me of the specialist fish tank gravel for aquatic plants), and more irregular in shape. Although Leca can vary in size, even smaller grade Leca it tends to be a lot larger than Pon (that's a scoop of Leca below) and shaped like a ball.
Some find the smaller size of Pon more root friendly for smaller or finer root systems, for less established root systems in younger or root-damaged plants, and for propagating. On a side note, when dropped, I love that Pon doesn't roll away, somewhere never to be found again, which Leca loves to do to me (seriously? every time).
Although price varies, the good stuff like Lechuza tends to cost more than Leca. For my budget, that means I save Pon for my plants more sensitive to over-watering, for propagation and for my babies, especially for my Hoya.
I don't have a budget that allows me to put every suitable plant in Pon (I wish) but it would take a lot to break up my love affair with BioLeaf which is the organic potting mix the majority of my more established plants are potted in. Pon is my new go-to for propagation since battling with some stubborn, harder-to-root cuttings last season (the change to Pon sorted them out).
If there's one big downside of Leca it's the transfer process. You really must get every scrap of soil off the roots when you change to Leca to avoid root rot. Root melt is common with Leca as soil roots die off and your plant adapts and produces water roots, which can be touch and go for less hardy plants.
Lechuza say you don't have to worry about soil remaining on roots when you transition plants to Pon, however I'd still recommend doing the best job you can to remove excess soil if you're going for the 100% Pon method. If going for the 25% or 50% methods (more about all 3 was covered further up), there's no need to remove soil or potting mix (or fern fibre, spagmoss or your substrate of choice), from around the roots.
Pon is much heavier than Leca or potting mix, as Pon is basically little stones. I love this for both my tiny fiddly pots when propagating, and well as the top-heavy big boys, to prevent tip-over. How light Leca is can be a pain with bigger plants in particular. Of course the weight of Pon is no good for most hanging pot situations though, where you want minimal weight.
In this area Pon and Leca are similar. Both eliminate some pests, and make others easier to manage. But neither are guarantees you'll suddenly be pest-free. Being soil-less, and super airy, both reduce the likelihood of soil-loving baddies like Fungus Gnats in particular, as well Mealybugs and Root Mealy along with moisture-loving pathogens like fungus.
Spider Mites don't seem to care either way what the substrate is as their entire lifecycle can be completed on foliage. Thrips don't seem to care much either, however are much easier to treat with Pon or Leca. Whatever pest you have though, treatment is much easier for plants in Pon or Leca vs plants in organic mixes like soil or potting mix, as repeated drenches and showering don't have the same high risk of over-watering and root rot as plants in soil or potting mix.
Leca has zero nutrients. Depending on the brand, Pon often comes with nutrients included (although typically only for the short-term). Both products are best used with a fertiliser made for hydroponics (GT and Dyna-Gro are the two popular hydro ferts in NZ for indoor plants).
Lechuza claims their Pon absorbs excess fertiliser, reducing the risk of fertiliser burn, keeping nutrients in reserve for plants when needed. Whether it does that better than Leca I'm not sure if that's been compared, but both offer that benefit to some extent. I haven't had this happen to me, but if you have baby plants in Pon that are also light feeders, the included fertiliser might be more than they need.
Depending on how you water now, you may need to change your watering method for Pon vs how you water with soil or typical potting mix (more about how to water when growing in Pon coming up), but Pon does regulate water better than Leca and stays moist longer and more evenly, making Pon more forgiving of neglectful watering compared to Leca. Using a water reservoir works with both Pon and Leca, but the 'shower watering' method is better suited to Pon. More about that coming up too.
Leca tends to require a lot of prep (here's how I do it). I can only speak for Lechuza-Pon, but from my experience, Pon requires far less if not no prep at all. In fact you'll often see it recommended to pot up in non-rinsed, dry Pon (that's because Pon holds water differently than Leca).
The zeolites included in most Pon mixes (including Lechuza Pon), helps maintain a healthy, slightly acidic pH without the need for adjustment, compared to Leca where manual pH adjustment is often needed.
How to water plants in Pon
The watering method you choose largely depends on the pot type. In a self-watering pot you can simply keep the water reservoir topped up once the plant's established. However the shower method is the best option for Pon in a normal nursery pot with drainage holes.
Like it sounds, the shower method just means a thorough top-water, really flushing the pon and roots thoroughly with water, letting excess freely drain out. This method needs a pot with drainage holes. This method is also used with Leca, especially at first to help a plant adjust to it. You want the Pon to be evenly moist throughout after watering (Pon slightly changes colour as it dries out).
Pon has excellent capillary action and stays more evenly moist throughout, so can also be used for wick watering, bottom watering, or with a water reservoir in a vessel without drainage. Feel free to experiment.
Top watering or the 'shower method' (which does not literally require a shower), is what works best for me but I'm planning to shift a few of my established plants to self-watering this season to save on maintenance time since they're a pain to shift to the sink.
You'll find you water less often with Pon vs most other substrates (depending on the substrate's water-holding capacity of course). Personally I heavily top water all my plants anyway, no matter what substrate they are in, so if you're like me, Pon won't require any change to how you normally water.
Important tip for self-watering and wick-watering with Pon
Pon is a favourite for using with self-watering or wick watering for the ultimate low-maintenance plant care. You'll typically only need to top-up the reservoir about once a month depending on the plant, time of year, and size of the water reservoir.
Keep in mind Pon distributes water better and more evenly than Leca, so an important tip is to leave the water reservoir dry for a while before topping it back up each time. This is called a 'dry phase' which - depending on the plant - can be a wait of 2 to 10 days before topping the reservoir back up. On average you'll water even less with Pon than Leca, and certainly much less often with Pon vs soil or potting mix.
How to transfer a plant to Pon
STEP #1 - PON PREP
The shift to Pon does have a few unique requirements. Unlike Leca, if you have a good source of Pon like Lechuza, you do not need to pre-rinse Pon before potting up, saving a huge amount of time. You can pre-rinse if you like, but it's not necessary. The first water after planting is normally plenty to flush out any dust or fines, however Pon is very low in fines compared to Leca. It's often recommended to plant in to dry Pon.
STEP #2 - PLANT PREP
If you're changing to 100% Pon, rinse your plant's roots thoroughly to remove as much organic matter as you can so you have nice clean roots ready to pot into Pon. It seems to be less important to have them 100% free of organic matter vs prepping plants for 100% Leca.
If you're just using Pon at the 25% (drainage layer only) or 50% method (drainage layer, side wall and top), you don't need to rinse the roots as the remaining 50% to 75% of your pot will be filled with your choice of substrate like potting mix.
STEP #3 - POT UP
Add a layer of Pon to the bottom quarter or so of the pot. Rest the root ball on that layer then fill the remainder with Pon, or if adding Myco for the roots, sprinkle a little Myco on the bottom Pon layer, directly under where the root ball will go, before adding the plant and the filling with Pon. Being smaller and heavier than Leca, Pon secures and holds plants in place better.
STEP #4 - WATER
After potting up, top-water thoroughly until the Pon is evenly wet and water really pours out the drainage holes. The same as soil or potting mix, you'll normally see the 'fines' wash out in the first water (cloudy brownish white particles), but nothing like the excessive fines you'd expect from Leca.
If using a self-watering pot or pot without drainage, tip out any excess water in the bottom. You don't have to fertilise, most Pon already includes short-term slow-release fertiliser, but can add a little seaweed to the water if you like to help the roots transition and recover.
The secret to this last step however is NOT to water again for at least 2 weeks if using the shower watering method (heavy top watering). If in a self-watering pot or wick watering with a reservoir, make sure to leave the water reservoir empty for the first 2 weeks.
Pon holds water better than Leca, so after the initial drench when repotting, step away from the watering jug! If your plant is really going through the wars and desperate for water before 2 weeks is up (normally for a plant that must be kept moist and can't handle drying out), you may need to water before 2 weeks is up.
For the majority of our aroids and hoya though, whether in a self-watering pot or not, give watering a rest for at least a fortnight after potting into Pon, adnd keep that water reservoir empty. At around the 2 week mark, the Pon will normally have changed colour as it's dried out. You can feel moisture with Pon so can also check with your fingers.
Go ahead and fill up the water reservoir a little now and check the water level is slowly going down over the next few days. If you see signs the water is being used, now you can go ahead and fill your water reservoir to the max and off you go as normal.
Does Myco work with Pon?
Yes! Myco will live and grow in Pon. The perfect time to introduce myco is when transferring a plant to Pon as the best place to add it is just below the root ball (it needs to be in contact with roots and below the surface, not exposed to sunlight). In hydro or semi-hydro, myco extends the root system and helps protect roots from pests and diseases (the brand I use is Seacliff Myco).
How long does Pon last?
This is a key difference to most other substrates. Pon is reusable, over and over again. Although it tends to be more costly up-front, it doesn't break down like most other substrates, and can last years. Not only will you need to repot less often, you can also keep any leftovers ready to reuse instead of buying more potting mix all the time.
Do you need special fertiliser for Pon?
In a way, yes. Although it does depend on your watering method. If you top water (the 'shower method'), then it's less important as top watering helps wash away excess fertiliser salts. If you combine your fertiliser with seaweed the seaweed will help 'fill in the blanks' for what your fertiliser doesn't provide (as most fertiliser are not complete). Plant Runner is one that does this for you, combining an NPK fertiliser with organic seaweed all-in-one. However what most people do - same as with Leca - is shift to a fertiliser formulated for hydro and semi-hydro.
Fertilisers for hydro and semi-hydro will normally be complete and balanced, including all 12 essential minerals, not just the 3 macro's (nitrogen, potassium and phosphorus), like many soil fertilisers do. I prefer hydro / semi-hydro fertiliser for all my plants, not just those in Leca and Pon.
Two of the best ones on the market here in NZ are Dyna-Gro and GT (Growth Technology). For light-feeders and plants more salt- and pH-sensitive, like Orchids, Hoya and some Aroids, Dyna-Gro and GT are free of urea, and GT is also free of chlorides (the most common, highest-salt ingredient in most fertilisers), and is pH balanced. Both are superb.
There you have it. The pros and cons, ins and outs, tips and tricks to growing plants and propagating in Pon or Lechuza Pon. If you have any other Pon questions I haven't answered here, please do get in touch. Always happy to help. Anna :)
Where can you buy Lechuza Pon in NZ?
Since I use it myself, I now buy Lechuza Pon in bulk for my indoor jungle, so when I have spare you're welcome to get some from me in 1 litre or 2 litre bags: shop Lechuza Pon here however if you're after it in bulk you will save more. Just search 'Lechuza Pon NZ' to find who's in stock in NZ of bulk (18 litre is the easiest size to source).