Pick cucumbers when they are the size you want, but they are better when….

Picked small and seeds are still soft: 3-4” for pickling types, 6-8” inches for slicers. A yellowish tinge at the blossom end indicates overmaturity. Pick often, especially during hot weather to encourage continued production. If possible, harvest in morning. They are sweeter then. Refrigerate them immediately. Don't wash them until you're ready to use them.