Liriodendron tulipifera Aureomarginatum, commonly known as Tulip Tree
Autumn Arrives in London
As our summer season ends and so autumn arrives in London and Great Britain.
The word autumn has ancient roots alluding to the passing of the year. In the USA and some parts of the world this season is called ‘the fall’.
This year, we have had mixed weather, from a wet and cold winter through a sunny and wet spring rolling into a sunny and wet summer.
We had two of the hottest days in September for over 100 years, with temperature reaching nearly 32C (89F).
Yes the British weather can still excite conversation among Brits. 😉
It is still quite mild with rain and sunshine and I can still wear a T shirt, without feeling cold. 🙂
The most common sign that autumn is approaching is when the leaves on deciduous trees. change colour from their spring and summer colour of green, to browns,yellows, reds and orange.
The leaves then soon after start to fall from their twigs and branches.
In autumn, some of the trees produce spectacular colour combinations of the above.
Deciduous is a Latin term meaning “falling off at maturity”
Leaves that fall off their tree branches in autumn are from the broad leaf type, having large areas to soak up the sun.
Trees that have these types of leaves need maximum food and energy to grow and produce fruit, such as apples, pears and berries etc.
These leaves have reached maturity by the end of summer using up the green chlorophyll pigment they contain to produce energy and food via photosynthesis for the tree in spring & summer.
As the daylight grows shorter with the arrival of the colder days of autumn and winter, the leaf receives decreasing amounts of warm sunlight.
The leaf can no longer produce enough food for it’s tree, therefore it will trigger a kind of self destruct sequence.
As the temperature lowers, the leaves try and remain above freezing to provide nourishment to the tree until the last possible moment.
As the green pigment fades in the leaf, other pigments appear, which were masked by the dominant chlorophyll.
One pigment is carotenoids, which produce rich yellow, orange and brown colours, such as in carrots, banana peel, pumpkins.
Another pigment produced is called anthocyanins which are mainly red and purple.
As autumn progresses, the leaves become weaker, insects feed and worsening weather take effect.
Within the stem of a leaf which is attached to it’s branch is the abscission layer, which chokes of the leaf veins that transfer water and food to the tree via the branch.
This further decays and weakens the leaf and stem, so the leaf becomes detached from it’s branch and so falls to the ground, it’s important work done.
Evergreen trees retain their leaves through cold freezing winter weather, because their smaller area leaves, some are needle shapes have a coating of a wax that helps protect them from the extreme cold.
Photo by PH Morton
Enjoy these wonderful seasonal colours and think of the sacrifice the leaf made to produce them.