How to recognise it
Plants become leggy and growth weakens. Scorched leaves wilt, turn yellow or brown (usually starting at the tips and margins) and may become dry and brittle and die (especially in a glasshouse where the leaves are touching the sides or roof).
In severe cases the stems can also die back, particularly the south west facing parts of trunks of thin barked trees such as beech, cherries, maples or poplars. A condition known as ‘heat canker‘ can also occur at the base of woody plants in hot soil, which usually heals satisfactorily without intervention.
On fruits, high temperature damage can become apparent by the development of discoloured patches on the skin, particularly on the upper surfaces (ie the ones which are most exposed).
What causes it
Very high or fluctuating temperatures in a closed environment (eg a glasshouse or home).
Why it’s a problem
Can weaken plant by wilting and eventually killing leaves. In extreme cases, the stem and entire plant can die.
Where you are likely to find it
In glasshouses where temperatures are not properly controlled. Plants with fleshy leaves or flowers, those near glass and seedlings are most likely to be affected. House plants can equally be affected.
How to prevent it
Ensure the temperature of glasshouses is appropriately regulated, eg through automatic ventilation systems. When appropriate, apply shading (either blinds or paint) to glasshouses.
Ensure that there are no faulty panes of glass which could increase the heat in a particular spot.
Do not allow plants to touch the sides or roof of glasshouses.
How to get rid of it
Affected leaves may not recover, but further damage can be prevented by taking the preventative action listed above.
Is it good for anything?!
Where properly controlled, high temperatures can benefit some plants. Plus, we humans do like a sunny day!
