Mulberries are one of my favorite fruits, but it's also the messiest to have in your yard. The yum-yum yummy berries are slightly larger than pea size and are a deep purple color when truly ripe. These berries come on quickly and don't last very long, so you have to enjoy them for the short time they are around, then they're gone until next year.
Typically the mulberries start ripening during the 1st or 2nd week of June and they will only last until the end of June. Birds loves these small seeded fruit, as evidence of purple splotches dripped on clean laundry hanging out on the line. The easiest way to harvest mulberries is to spread a sheet or tarp on the ground under a tree and then shake the tree branches. The fruit will tumble to the ground. Mulberries are extremely soft when ripe and they do not store well, so it is best to eat them fresh.
Although I don't raise silk worms, I do know the silk worms main food source is mulberry leaves. I can remember going to the Shaker Village at Pleasant Hill - the largest historical Shaker Museum in America - to see the silk worm exhibitions. Silk worms are no longer raised at Pleasant Hill, but they do have the occasional traveling silk worm exhibits.