They should be ready to pick this is Sept 9.....color green for the acorn....test the skins with a light touch of your fingernail...hard to pierce it is ready...dry stem is the next thing to look for.....leave 2 inch stem...don't pull, just cut off.
The butternut get a slightly different color when it ripens...about 10 to 14 inches......leave 2 inch stem...if you are going to store for winter, you have to use clean damp cloth and wipe them off......let them sit out of the sun to harden then store in a cool dark place for 3 to 6 months.