Environment Heat stress
Limp leaves in high heat
The plant flops in the hottest hours and picks up again in the evening.
Also called: heatwaveheatlimp leavestoo hot
Severity
Keep an eye on it
Deal with it this week, before it spreads.
Parts affected
- Leaves
- Stems
- Flowers
- Fruit
- Roots
- Soil
Family
Environment
Cold, heat, dry air, shock after repotting: what comes from around it.
Understand
What is happening inside the plant
Above a certain threshold the plant transpires faster than its roots absorb: it closes its stomata to protect itself, which also stops photosynthesis.
The foliage flops in the hottest hours and recovers when the temperature drops, that daily cycle is the signature of heat stress. Repeated, it drains reserves, aborts flowers and fruit, and scorches the most exposed leaves. Heat alone is enough: the substrate may be perfectly moist.
Check
How to be sure
Tick what you can see on your plant.
Tick the signs you can see and the gauge will add them up.
Some signs match. If the rest does not fit, look at the related problems further down.
Most of the signs match: this is very likely it. What to do
Signs and causes
What you see, and why
Symptoms
- Leaves limp through the day, recovering at night
- Soil drying out in under a day
- Growth stopping in mid-season
Causes
- Temperatures sustained above thirty degrees
- A plant behind glass with no shade
- A dark pot in the sun, heating the roots
What to do
The action plan
In order. Tick each step once it is done.
0/3 done
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Move the plant into shade during the hottest hours.
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Water early in the morning, more deeply but no more often.
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Do not fertilise during a heatwave.
Prevent
Stopping it coming back
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Shade south-facing positions in summer.
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Choose a light-coloured pot outdoors.
Questions
Common questions
Should I water a plant that flops in heat?
Check with a finger first. If the soil is moist, watering will not help and will drown the roots: it needs shade, not water.
When should I water in a heatwave?
Early morning. The water has time to move down before peak heat, and the foliage does not stay wet overnight.
Is shade netting worth it?
On a balcony or in a conservatory, very much: cutting sunlight by thirty to fifty per cent is enough to get through the day.
Keep an eye on it Cold-blackened leaves
Leaves blacken or drop on the side facing a window or a door.
Causes and fixes
Keep an eye on it Sudden damage after the weather
Sudden damage after extreme weather such as frost, heatwave or wind.
Causes and fixes
Minor Brown, dry tips
Leaf tips and edges brown and dry.
Causes and fixes