This is sun scorch (sunburn) on a begonia leaf, common at this time of year (midsummer) when moving plants too quickly from shade into strong sunlight.Although plants are classified according to their light preferences - e.g. shade-loving; sun-loving etc - this is not absolute. We saw last year that, given time, plants can adjust to almost any environment (see posts on 'light').
PLANTS TAKE IMMEDIATE AVOIDING ACTION
Although begonias do not seem to be able to do this very well, plants can often react quickly by altering leaf turgo pressure (there are different ways of doing this), causing them to either follow or avoid the sunlight. For example, begonias (shade-loving plants) flute their leaves (common with many plants).
LONG-TERM ACTION TAKES TIME
However, they also GROW into their new environment and develop a thick waxy cuticle on the leaf surfaces to protect against damaging ultra violet rays; leaf size is also reduced in bright sunlight, and vice versa.
REMEDY
Leaf structural damage is permanent; they will not recover. However, if the disfigurement can be tolerated in the short term, it is worth leaving the damaged leaves in position because:
- there will usually be some undamaged tissue left which will speed growth of new leaves
- they offer shade to young tender leaves
2 comments:
We live in the north-east of Scotland, and I have recently put my begonias outside. I believe the leaves are either scorched by the sun, or burned by the wind - or both! Reading the information, I gather the new leaves will develop a protective screen.
Thanks for your comment. At this time of year, when the sun is very strong, this will almost certainly be your problem.
This sun scorch problem occurs in this way because there has been insufficient time for the plants to develop a waxy protective cuticle, which they will on the new leaves formed.
Be aware, though, that this growth may not come as expected if the growing tip - the apical meristem - has been damaged. This does not often happen as plants tend to hide these sensitive plants under their foliage. But it can.
Plants kept indoors in high humidity are also very delicate and subject to scorch through dehydration. The waxy cuticle will help this too.
The key thing is to do things gradually with plants. Then it will never cease to surprise you how they will survive even the most adverse conditions.
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