Why do my plant's leaves curl up?

In a plant, curling leaves are a cry, an SOS, a bottle to the sea. It's a sign that something isn't quite right, and that it's in danger of dying. So you need to act fast. But before you can intervene, you need to identify the problem that's causing the limbs to curl up. Whether it's watering, light, temperature or fertilization, we explain the possible causes and how to remedy them.

When your Pothos or Calathea picturata rolls up its leaves, it limits the surface area exposed to the sun. This helps reduce evaporation and water loss.

More often than not, your plant rolls up its leaves when it runs out of water. This happens if you've forgotten to water it for a long time, or if your watering is irregular or not copious enough. To be sure, touch the substrate. Is it dry on the surface and deep down? Get out your watering can. If there's a gap between the pot and the soil, the soil is completely dehydrated.

You should then water copiously, until the water runs off through the drainage holes. But if the soil is too dry, it can no longer absorb water. You'll realize this in the first few seconds: the water will escape as soon as you pour it in, without penetrating the potting soil. In this case, it's best to water by capillary action: fill a container with water at room temperature and place your plant's pot inside. Leave it to soak for at least 15 minutes to rehydrate the substrate and the plant.

Plants can also run out of water through overwatering! When a plant is over-watered, its roots rot. They can no longer drink and feed the stems and leaves. And the leaf blades curl up to reduce water evaporation.

Inspect the potting soil to see if your plant is suffering from excess water. Even thirsty species like papyrus or alocasia zebrina need their substrate to be moist, not soggy. If the soil is muddy, you've over-watered. Another symptom to confirm the diagnosis is the condition of the roots. Healthy roots are firm and light-colored. Rotted roots turn brown, soft and smelly.

No stress! It's not necessarily too late to remedy the situation. Start by taking the unfortunate plant out of its container and removing the substrate. Cut off the rotten roots with a clean, sharp pair of pruning shears. Then replant in a pierced pot with a new, draining potting soil suited to your plant. Not sure which one to choose? Download the Monstera application. We'll advise you on the type of substrate to use for each variety.

In houseplants such as tomatoes, lemon tree and other garden-grown varieties, curling leaves can be the consequence of a pest attack. Biting and sucking insects such as whiteflies, aphids and mealybugs bite foliage and stems to suck out sap. This has the direct effect of stunting the leaf blades, which curl in on themselves.

Examine the leaves to see if your plant is affected by pests or disease. Look for stings, rot and honeydew (a sticky film). You may also find insects, larvae and whitish masses.

Is your plant invaded by parasites? Isolate it from the rest of your collection and cut off the most affected parts. Most of the time, a shower in lukewarm water and a wipe down of the leaves with black soap is enough to get rid of the unwanted pests. But if you're faced with mealybugs or a severe infestation, you'll need to resort to insecticides and pheromone traps.

Pests and diseases are rampant when growing conditions aren't right. In particular, they can be found when humidity levels are inadequate. To prevent your indoor jungle from being attacked, return to a proper maintenance routine. Water regularly, but not excessively, ventilate and make sure there's enough light. Finally, inspect the leaves of any new specimens you invite into your home. Bugs are sometimes sold with the plant! If in doubt, quarantine the newcomer until you're sure it poses no danger to the rest of your collection.

Curling up the leaves protects the plant from the cold and heat. The varieties we grow indoors are often native to tropical or desert areas of the globe. They generally appreciate temperatures between 15 and 25°.

If your plant curls up its leaves in winter, it's probably because it's cold and you're not heating it enough. Move it to a room where the thermometer reads at least 18°. Plants also suffer during heatwaves. To protect them from the heat, keep them away from windows, mist them regularly and increase the frequency of watering.

Is the temperature ideal, but your plant isn't putting out its leaves? Perhaps it's been placed in a draught. Once again, the remedy is simple: move your pot!

Are the leaves on your Stromanthe sanguinea curling up and pointing downwards? The plant is probably trying to fight against too much light.

This tends to happen in summer, when you take your plant out into the garden to enjoy the fresh air. Unaccustomed to these new growing conditions, your plant will fold up its leaves to limit its exposure to the sun. Move the pot to the shade and gradually get your plant used to life outdoors. Start by taking it outside for a few hours in the morning or evening. Gradually increase the duration and intensity of exposure. Even after a few weeks, be careful to keep to the recommended exposure so as not to burn the leaves. Some varieties like part shade, others bright light. But only succulents and cacti tolerate direct sunlight.

Our green plants rarely receive too much light indoors. Unless you live in a very sunny region and place a shade-loving species (Marantaceae or aglaonema costatum, for example) behind a bay window that is too bright. For the latter, choose east- or west-facing windows. Do you live in Nice and face due south? Move pots back a metre from the window or install a curtain to protect your plants from the hottest hours of the day.

In our homes, plants are more at risk from a lack than an excess of sunlight. A plant that lacks light doesn't curl up its leaves. Instead, it tends to turn them towards the sun.

Finally, leaf curl can be caused by a nutrient problem. Here again, there are two options.

The most common? Your Ficus elastica 'Tineke' has been in its pot since you bought it, and you've never repotted it or given it fertilizer (you can even combine the two). The soil is depleted of nutrients and your plant is hungry. Curling leaves aren't the only symptom. Growth slows down, your shrub stops growing and doesn't produce new limbs.

To remedy this, give your plant some fresh potting soil! Repot it in a larger pot. If it's too big to handle, resurface it. Remove a third of the soil with a claw and replace with a suitable substrate.

In the case of zealous gardeners, leaves may curl up due to excess fertilizer. Overdosing occurs when you don't respect the frequency or doses prescribed by the manufacturer. Other signs indicate that your plant has been over-fertilized. For example, brown spots appear on the foliage.

There are two solutions to this problem. The first is to leach the soil, i.e. Water very heavily to remove some of the nutrients. You can do this indoors, in your shower. But it's best to leave your plants in a summer shower to benefit from the rainwater.

You can also opt for repotting. Even during the growing season, you should wait at least four weeks after repotting before resuming fertilization. The new substrate is perfectly balanced and provides your plant with what it needs, without excess. No need to add more! The roots won't be able to keep up and you risk damaging the leaves.

Want to avoid making the same mistakes again? Find out more in our article on How to fertilize indoor plants?!