TL;DR
A heatwave doesn't have to mean sacrificing your house plant collection. Check the soil rather than the calendar, water deeply in the morning, keep plants out of direct hot sun, boost humidity for tropical plants where you can, and pause fertilising and pruning until things cool off. A little extra attention now will have your plants back to full health as soon as the temperatures drop.
It looks like heatwaves and summertime temps over 30°C are here to stay in the UK. Whilst we get used to this new normal, it's easy to focus on keeping yourself cool and forget that your house plants are probably struggling too. Most of the plants we keep indoors originally came from tropical regions near the equator, so they can generally handle heat better than cold. That said, once temperatures indoors creep above the mid-20s°C, even hardy tropicals can start to show signs of stress. Here's how to keep your indoor jungle happy when a heatwave hits.
Which houseplants are most at risk in a heatwave?
Not every plant struggles equally when the mercury rises. Tropical foliage plants that naturally grow under a forest canopy, such as ferns, Calathea, Maranta and Begonia, are used to shade and consistently humid air, so they tend to be the first to droop or scorch when a room turns hot and dry. Larger-leaved plants like Monstera and rubber plants can also show sunburn if they're moved into stronger light than they're used to.
Cacti and succulents sit at the other end of the scale. Varieties like Sansevieria (snake plant), Haworthia and aloe vera are adapted to heat and drought, and can generally get through a heatwave lasting several weeks with little more than your normal care.
If you know a heatwave is on the way, it's worth checking on your shade-loving, thin-leaved plants first. They're the ones most likely to need a change in routine.
1. Ditch the watering schedule
The single biggest mistake people make in a heatwave is sticking rigidly to their usual watering routine. Higher temperatures dry out soil much faster than normal, so a "once a week" schedule that worked fine in spring may leave your plants gasping in July.
Instead of watering by the calendar, check the soil itself. Push a finger a couple of centimetres into the compost. If it's still damp, hold off. If it's dry, it's time to water. For a quicker check, you can also lift the pot: a pot that's dried out will feel noticeably lighter than one that's freshly watered.
Just be careful not to overcorrect. Watering too often can drown the roots just as easily as under watering can dry them out, so always check before you reach for the watering can.
2. Water at the right time, the right way
Morning is the best time to water. It lets your plants take up moisture before the heat of the day increases evaporation from both the soil and the leaves, so they start the day well hydrated and better equipped to cope. Watering in the middle of a hot afternoon is far less effective, since a lot of that moisture evaporates before the roots can use it.
When you do water, water deeply and slowly rather than giving a quick splash on top. A fast pour often just wets the surface before running straight down the sides of the pot. Let the water soak in properly, and if your pot has a saucer, empty any standing water after 15–20 minutes so roots aren't left sitting in a puddle.
Always use room-temperature water. Water straight from a cold tap can shock the roots, so keeping a jug filled and standing nearby is a simple habit worth building.
3. Rethink where your plants are sitting
A spot that's perfectly sunny in spring can turn into a scorch zone in a heatwave. Move plants away from south- or west-facing windows, where indoor temperatures can soar even if the plant itself isn't in direct sun. Sunburn typically shows up as rough brown or yellow patches on leaves and stems. If you spot this on something like a pothos or similar tender-leaved plant, move it a little further from the glass.
That said, don't banish plants to a dark room to protect them from heat. They still need light to survive, even during a heatwave.
Air conditioning is still fairly rare in UK homes, but if you're lucky enough to be in one of the households that has it, keep plants away from the units and vents. Air conditioning strips both heat and humidity from a room, and that combination of dry, cold air is a shock to tropical plants used to warm, humid conditions.
4. Boost the humidity
Warm weather often means drier air indoors, and many popular houseplants (think ferns, Calathea, Maranta and similar tropical foliage plants) really suffer when humidity drops. A few easy fixes:
- Group plants together to create a shared, more humid microclimate.
- Use a pebble tray filled with water underneath pots (make sure the pot itself sits above the waterline, not in it).
- Mist foliage with room-temperature water a few times a day if your home is particularly dry.
Cacti and succulents are the exception here. They're used to heat and drought and generally shrug off a heatwave with little extra care.
5. Hold off on the fertiliser
It's tempting to want to give a struggling plant a boost, but fertiliser is the wrong move during a heatwave. A heat-stressed plant is putting all its energy into survival, not growth, and isn't able to take up nutrients properly. Feeding it anyway can actually burn already-stressed roots. Wait until temperatures settle back down and the plant is growing steadily again before resuming your normal feeding routine.
6. Don't rush to prune
If leaves have scorched or turned brown, it's natural to want to tidy them up straight away. Hold off. Damaged leaves can still be providing shade and protection to the healthier growth underneath, so it's best to leave them in place until the heatwave has properly passed. Once temperatures are back to a comfortable 20–26°C and the plant is showing steady new growth, you can trim away the worst of the damaged foliage and let it focus on recovering.
Quick Questions
How do I know if my plants are struggling in the heat? Keep an eye out for wilting or drooping leaves and stems, leaves turning pale or losing their usual vibrancy, brown or yellow scorched patches or flowers or leaves dropping off. Catching these early gives you the best chance of turning things around before any lasting damage sets in.
Should you water plants more in a heatwave? Often, yes, but not automatically. Heat dries out soil faster, so plants may need water more frequently. The key is to check the soil each time rather than watering on autopilot, since overwatering can be just as damaging as letting a plant dry out. Cacti and succulents may not need extra water in the heat as they thrive in hot, dry conditions.
How do I stop my houseplant's leaves from scorching? Move it out of direct sun, especially away from south- or west-facing windows where indoor temperatures build up fastest. A spot with bright, indirect light is usually enough for most houseplants, even in summer.
Can houseplants overheat? Yes. Once room temperatures climb much above the mid-20s°C, tropical house plants can start to wilt, drop leaves or develop scorched patches, even if they're getting enough water. Moving them somewhere cooler and improving airflow can help bring the temperature around them down.
