Why are your Watermelon Peperomia leaves curled, cracked and splitting? (and how to fix them)

Do your Watermelon Peperomia leaves curl and crack? Same! Here’s what I did to fix mine and the 5 common causes to help you fix yours too…

#1 The air is too dry.

If you’re not underwatering, dry air can cause cracked, split edges. Especially in winter when heating sucks the moisture out of the air. You don’t need to go overboard, as too much water or humidity can cause leaf or root rot. Maintaining an average humidity of 50% to 60% is great, and the same range most of our tropical indoor plants are happy in. The average heated home however drops to around 30% in winter.

But before you rush to get your plants a plant humidifier, check humidity first using a hygrometer. You should be able to pick up one of those little digital ones that check temperature and humidity for around $10, like these 2 in 1 meters for those in New Zealand, or these 2 in 1 meters from Amazon for my overseas readers.

If the humidity often drops below 50%, even a small area humidifier will make a big difference. My go-to are the H2O Cordless Humidifiers (I mainly use the 750 model for my jungle), and the rest of your plants will likely love the extra humidity too. If you're not in New Zealand though, Levoit on Amazon has a top-rated range of affordable smaller humidifiers too, popular with plant parents.

#2 Calcium deficiency.

This turned out to be the key to fixing my Watermelon Peperomia. I fixed everything else on this list, which absolutely did help, but still got curled, cracked leaves (just not as bad as before). So frustrating! I almost gave up on mine. Some leaves had weird, almost deformed shapes too.

Off to Dr Google I went. I had heard Peperomia in general like calcium. So I tried watered-down milk and eggshells, but my Watermelon Peperomia was still a problem child. Plus the milk attracted fungus gnats! No thank you.

In the end the combo of an immediate calcium boost from dolomite lime (you can get Yates Dolomite Lime in New Zealand, or E & Lay Dolomite Lime on Amazon),  combined with changing to a fertiliser that had calcium in it did the trick. And wow, what a difference. Except you might run into the same problem I did at first. Most fertilisers don't include calcium. Probably why so many Watermelon peperomia suffer in the first place!

My hands-down favourite fertiliser for my calcium-loving Peperomia is GT Complete Focus (for those in NZ), and GT is also available on Amazon for those overseas. Actually, all of GT's Focus fertilisers include calcium, but Complete Focus has the highest calcium levels. Another of the few that do include calcium is Dyna-Gro, now under the Superthrive brand. In that brand have a look at Superthrive Foliage-Pro (in NZ), or Foliage-Pro is also on Amazon. GT averages 100ppm calcium once diluted, vs Dyna-Gro which is around 20ppm calcium (depending on dose for both, that's just going by their general maintenance doses).

If you've tried dolomite lime by itself, but haven't seen a big difference in the new growth (remember you can't fix old growth), that might be because your plant's missing the other nutrients it needs. It's no good giving your Watermelon Peperomia crazy amounts of calcium if the other essentials are out of whack, as a deficiency in other nutrients can prevent your plant from absorbing the calcium it needs. 

Another reason why giving calcium in the form of a complete and balanced fertiliser is better than a source of calcium by itself. Calcium also helps plants handle environmental stress better when other conditions aren't perfect, and helps flowering plants hold onto flower buds, then flower for longer too. Win win.

#3 Your soil is too dry.

Watermelon Peperomia retain water well in their leaves and stems, but being scared of overwatering means you might be underwatering (hands up on this one for me, I was definitely guilty of this at first). 

Sure, let the soil dry out on top, but not all the way down! Left too dry for too long, Watermelon Peperomia leaves can curl inwards to conserve water. Remember water, light and heat go together. Kept in a bright, warm spot (which they love), they need watering more frequently than you might think. Aim to maintain the soil lightly moist and use a substrate that's light and airy to avoid ever becoming waterlogged. I stay away from soil-based and peat-based substrates for that reason. 

If in doubt, get a water meter to check moisture at root level. There are so many different types of water meters it gets confusing, but these are the best 3 I've used depending on budget:

The colour-changing Sustee water meters are fantastic if budget allows (if you're not in New Zealand, you can also get Sustee on Amazon). They're small and stay put in your soil, changing colour from blue to white when it's time to water. The most accurate moisture meter I've tried in my plants.

But if you want to save your pennies for your plants, get yourself a cheap 3-in-1 analog water meter that you can move from plant to plant (or for those overseas, you can get similar on Amazon here also). Not as accurate but a great back-up for your own judgement for peace-of-mind.

Or a good in-betweener that's still budget-friendly but also more accurate, and you only need one for your entire jungle, are the Crew Soil Sensors. That type is a digital meter that you can shift from plant to plant that flash a different colour depending on how moist the soil is.  

#4 Temperature check (highs and lows).

Warm is good when you're a Watermelon Peperomia. But not too hot. Around 18 to 25 degrees during the day, ideally not below 15 at night. Leaves can split, crack and curl if things heat up too much, especially combined with dry substrate or dry air.

Keep an eye on humidity and those top temperatures. No need to spend a fortune though, those same cheap hygrometers to monitor humidity also check temperature for you, like these 2 in 1 meters available in New Zealand, or these 2 in 1 meters from Amazon.

#5 It's too dark.

Bright indirect light is ideal for a happy Watermelon Peperomia. If light’s too low, stems can get long & leggy, new leaves can come in small, leaves can curl, and variegation can change. Try a move to somewhere brighter, but I find it best to avoid sun directly hitting the leaves or you could be dealing with crispy sunburned leaves instead. Ouch.

The moral of the story is please don't give up on your Watermelon Peperomia! It is possible to get those glorious big shiny, smooth leaves without curled, split, cracked edges. I really hope these 5 causes help you fix yours like they did mine. Please share with a fellow Watermelon Peperomia lover to help them too :)