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 one secret to how collectors with a huge indoor jungle can manage to care for hundreds (or in Kaylee 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.
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. Changed to Pon and they took off.
Since then I've had great results in my Aroids in general, and especially my Alocasia (including finally escaping the 'one leaf club' where I lose a leaf every time a new one was on the way). 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 Lechuza and in NZ we can now get Bio Pon from Bio Leaf, 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 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. Normally a combo of pumice, lava rock and zeolites but there are small variations between brands and some also add fertiliser (which you need to be aware of if yours does).
Lechuza Pon uses pumice, zeolites, lava rock and slow-release fertiliser. NZ made Bio Pon uses the same (pumice, zeolites and what we call scoria, also called lava rock), but is fertiliser-free which a lot of hobbyists prefer. Overseas, Lechuza Pon now sells a version without fertiliser also (in NZ our version is the original that includes fertiliser).
Depending on the exact mix, Pon maintain a ratio of around 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 many more. When used for moisture-loving plants however, like Peac Lilies, you'll likely be best combining Pon with potting mix. More about that coming up.
What are zeolites?
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?
A VERY important one when you enter the world of Pon. This also relates to the earlier mention about the fertiliser in Lechuza-Pon.
Some Lechuza substitutes don't include fertiliser (which is good), but because the original Lechuza Pon does include a slow-release fertiliser, although you do not have to fertilise right away, you DO still need to fertilise long-term.
If your pon is fertiliser free you can and should start fertilising straight away.
I personally prefer to stay in control of what I feed my plants, when, and how much, to do what I can to avoid fertiliser burn or defliciencies. If using Lechuza Pon, skip 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.
If you can find yourself a fertiliser-free version of Pon, like Bio Pon, fertilise as normal.
Do you need to change fertiliser when using Pon?
Yes. Pon itself is sterile. Normal NPK fertilisers are made for plants growing in organic substrates. Most soil fertilisers rarely offer everything a plant needs, as fresh, organic soil will also provide added minerals and is 'alive' with microbes and beneficial bugs that break down those organics into nutrients.
Shift your Pon plants onto a fertiliser that says it is for semi-hydro and hydroponics, such as GT Focus (Growth Technology), or NurtureSystem (that's Kaylee Ellen's fertiliser).
In Pon, it's all on you to provide all the minerals your plants need. Look for a fertiliser with all 12 essential minerals.
Personally I also like to avoid high-salt ingredients since it's the salts in fertiliser than can cause fertiliser burn. So I also like my fertiliser free of sodium, chlorides and urea. Depending on how sensitive your plant is, you might also like to find one without nickel or cobalt, phytotoxic to sensitive plants even in small amounts.
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.
The 50% 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's true semi-hydro. It involves removing all organic matter like soil and potting mix, rinsing the roots well, then planting fully in Pon.
The 100% method is also popular for avoiding pests (mainly fungus gnats, but more about pests coming up).
The other way Pon can be used is for mixing evenly into your soil or potting mix at your preferred ratio to make it heavier, airier and more free draining.
Where can you buy Pon?
Lechuza Pon is available on Amazon and for those in New Zealand, (when I can get it), I also sell Lechuza Pon in NZ locally. For those in NZ, you might have more luck getting Bio Pon which is NZ made and fertiliser-free.
What are the differences between Pon and Leca?
SIZE
Pon tends to be much smaller, like small gravel (it reminds me of fish tank gravel), and more irregular in shape. Although Leca can vary in size, even smaller grade Leca it tends to be a lot larger than Pon 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).
TRANSFER PROCESS
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 (and expected) 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 highly 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 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.
WEIGHT
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 tends not to be the best solution for hanging pot situations though, where you want minimal weight.
PESTS
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.
Whatever pest you have though, treatment is 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.
FERTILISER
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 like GT.
WATERING
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.
PREP
Leca tends to require a lot of prep (here's how I do it). 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). However, I still strongly recommend you prep the same as you would with Leca for better results with Pon.
pH
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 or you can water until water overflows. 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 better 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.
Important tip for self-watering and wick-watering with Pon
If you got Pon specifically to give self-watering a go, have a read of the Ultimate Guide to Growing Houseplants in Semi-Hydro with Leca or Pon next >
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 lower in fines compared to Leca. It's often recommended to plant in to dry Pon but I only pot into already soaked Pon.
STEP #2 - PLANT PREP
If you're changing to 100% Pon, rinse your plant's roots super 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 but I still pay extra attention to this step to reduce the risk of root rot while the plant adjusts.
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. 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, rinse repeatedly, tipping out any excess water or letting the water overflow. You don't have to fertilise if using Lechuza Pon, but if using Bio Pon or another fertiliser-free Pon, add fertiliser to the water reservoir or final water through after rinsing.
To help the roots transition from soil to Pon, you can leave the water reservoir empty for the first 2 weeks and manually water instead just at first as the plant shows it needs it.
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, and keep the 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 now and check the water level is slowly going down over time to make sure the plant is using it.
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. You can soak used Pon in hydrogen peroxide to sterilise it between plants. I use OXY 3% or Forsana Plant Care Plus.
There you have it. All the basics for giving Pon a go. Check out the Ultimate Guide to Growing Houseplants in Semi-Hydro including Leca and Pon next...
Read the Ultimate Guide to Growing in Semi-Hydro next >