The fall of the leaf, the ripeness of the fruit
The traditional English word in England for this time of year was fall, not autumn. Fall isn’t a modern American import at all. Fall is short for ‘the fall of the leaf’ and was in common usage in England in the 17th Century. Autumn is a new and fancy word for fall which came to the English language from the French autumne and only began to be used commonly in the 18th Century.
It’s not just leaves which are falling now though, it’s fruit which is ripening:
Together with the changing of the colours of the leaves the intensity of the red of the ripening fruit is a wonderful sight: