These trees are considered deciduous plants.
In our climates, there are two major types of foliage among trees and shrubs: evergreen, whose leaves live on average two years, and deciduous, whose leaves fall each fall.
But we also observe that certain species of trees keep their leaves dry (marcescent) for part of the winter.
What are these species with marcescent foliage?
Oaks, beeches and hornbeams have opted for this technique Why this situation?
If the leaves fall in the fall, it is because of the harsh winters when they can no longer work normally. On the contrary, it could be detrimental to the survival of the plant.
For evergreen shrubs and shrubs native to our regions, we observe that they are very often plants that grow in the undergrowth: boxwood, holly for the most common. They thus benefit from protection against the cold from the high foliage of the forest trees and can put the brightness of the winter because in summer the canopy makes a lot of shade.
For marcescent foliage, there are several explanations:
These rather tough leaves will partly protect the eyes of the branches from the browsing of large herbivores (deer, roe deer, fallow deer).
These leaves are partially degraded during the winter by light and will only enrich the soil litter in the spring, avoiding a loss of mineral nutrients during the winter.
Finally, the cover of the leaves of the lower branches acts as a shade which slows down the melting of the snow and prolongs the supply of water at the end of winter, when the trees need it.
When a fruit tree retains its leaves in autumn, is this normal?
On the other hand, when a cherry tree retains brown leaves in autumn, this is not a good sign, because the leaves that remain attached have not been able to complete their vegetative cycle normally. This is a sign that they are suffering from a dangerous long-term fungal disease: red spot disease, Gnomonia erythrostoma.
On other deciduous trees, the persistence of brown leaves on the twigs is a very bad sign, it means that the twigs, or even the whole tree, are dead. This symptom is usually accompanied by wrinkled twigs, signs of the absence of sap. bacteria, such Erwinia amylovora (bacterial fire) may be the cause.
Particularly hot and dry years can kill trees or shrubs during the summer. it is then observed that the leaves turn brown and remain attached to the twigs, whereas for plants that have undergone less significant stress, the leaves have yellowed and then fallen.
The only ways to combat such diseases are prophylactic:
Copper treatments at leaf fall,
· Disinfection of tools, especially cutting tools.
Ask all your questions during the gardening program on Sunday morning on France bleu Isère from 9 a.m. to 10 a.m. by calling 04 76 46 45 45