How can you tell when a cucumber is ready to be picked?

Question

How can you tell when a cucumber is ready to be picked?

Answer 1

They can be picked quite young. They are excellent mid-sized.  

But don't let them get big, they will be tough and seedy.

If they do get big pick them  right away and compost them. The vine would rather work on that old seedy monster than start a bunch of new delicious ones. You want food, the vine only "wants" to reproduce (seeds).

So it's not critical when you pick them unless they are big, then it is critical to pick them to keep the vine productive. Eventually the vine stops producing anyway so it's a good idea to plant several plantings over a few weeks to increase the time you can get the fresh food.

Answer 2

Jeremiah stole my answer.  He got here first and said it better than I could have.  He is absolutely right on the money.

Answer 3

When it is as big as you want it, but before it turns yellow