Pruning walnut tree

Question

We have a large walnut tree in our garden and it needs pruning back as it’s blocking out a lot of sunlight in our garden. When is the best time of year to do this?

Answer 1

The best time of year to prune the Black Walnut Tree is when the sap is up in the tree, not coming up.
That would be about in spring, before the tree begins to leave out.
Do not prune in Fall or Winter. You don't want to open an injury when the tree has no time to heal.

https://www.gardeningknowhow.com/edible/nut-trees/walnut/planting-walnut-trees.htm