As David Hockney today, Sperl experimented with the play of light among the trees:

Oils

Oils, 104x82

 Oils

 1981, Oils, 65x80

 1983, 130x100

Oils, 60x80, Unsigned, Undated

His last picture that was still on his easel at the time of his death is a forest scene:

Oils, 80x100

It is noticeable, however, that his trees and forest scenes become increasingly stylised and symbolic.

So for example this painting, whose theme is the seasons in the Bohemian Forest:

 Oils

 

The essence of the Bohemian Forest is distilled in the following painting: the tree, the house, the das star, ohne without which there would be no life:

Oils

The various pines in various ones perhaps symbolises the stages of human life:

  1968, Oils, 100x130

 
This picture sums up the essence of Sperl’s art and philosophy: The Bohemian Forest with its typical farmhouse, its most famous mountain, the Arber; working the fields, fertility; the young tree as the young man, the golden time of life, man and wife together, age and decay; the cycle of life accompanied and influenced by the cycle of the stars; clouds that look like Wotan’s horses and a juniper bush which, according to legend, protects from misfortune and guards the entrance to hidden treasure:

 
1962, Oils, 127x97

This painting hung in Sperl's studio until his death. It obviously meant a lot to him.