Houseplant clinic: why are my calathea leaves curling?

Asking yourself 'why are my calathea leaves curling'? We're here to explain.

Calatheas are among the most beautiful houseplants, with highly ornate, patterned leaves that can be round, oval, or spear-shaped. They are highly prized for their decorative look and are relatively low-maintenance.

However, like all of the best indoor plants, calatheas can suffer from ill health, and curling leaves are a sure sign that your plant needs a bit of help. We've asked houseplant experts to identify the reasons why a calathea's leaves may be curling, and how to nurse your plant back to health. 

Why are my calathea leaves curling? The experts explain

Jo Lambell, houseplant expert and founder of Beards & Daisies, recommends paying attention to two things if your calathea leaves are curling – a change in temperature and a lack of water. 

Jo's top tip is 'to never let your calathea dry out, they prefer to be kept in moist soil at all times.' Performing the finger test, that is, seeing if the top two inches of the soil is dry, is a good way to tell if it's time to water. Generally speaking, a lack of ambient humidity can cause curling leaves – 'Increase your calathea plant’s humidity levels by misting with lukewarm water, positioning on a pebble tray, or finally, by grouping them together with other plants.'

Watering plants incorrectly is almost always at the source of any problems, and overwatering can be as damaging to calathea leaves as under-watering. Pol Bishop, a gardening expert working for Fantastic Gardeners, explains that 'If the leaves of calathea are still wilting even though the soil isn't dry, the plant might have been overwatered and its roots have started to rot. Consider uprooting the plant and examine them thoroughly.' If the roots have started going black, you'll need to repot your plant into fresh soil.

Tropical plants dislike huge temperature fluctuations, and this is true of calatheas. According to Jo, you should be wary of positioning your calathea too close to 'a heat source such as radiators or drafty windows – temperature influxes will also cause curling and unhappy foliage.'

Pol agrees and says that 'the plant thrives in a temperature between 60–85°F (16–29°C). With that in mind, make sure you regularly monitor the temperature of the room where the plant is and adjust it if needed.'

Strong sunlight is another big no-no when it comes to calathea care. Pol urges indoor gardeners to move calatheas away from direct sunlight as they 'can't stand' it. Calathea leaves 'will get permanently damaged if exposed to constant and strong sunlight. Move them away from the window, but make sure to place them somewhere with partial sunlight.'

• You can find plenty of inspiration for indoor garden ideas in our feature.

Finally, if you've tried everything and your calathea leaves still look unhappy, the culprit may be the water. Pol explains that 'water that is hard and rich in salt and other minerals is toxic to calathea plants.' 

If you live in an area with hard water, you may find that watering with rainwater or bottled water works better, or 'consider distilled water' for watering your calathea.

Work through these possible reasons using the process of elimination, starting with watering, and moving on to position, temperature, and water quality if watering isn't the issue.