Pick them when they are the length you want to eat. If you leave them they will start to fern and be tough and not good for eating. You can refrigerate them a few days and combine a couple of cuttings if you want to have a decent amount for a meal. Eight plants seldom produce enough to cut at one time for more than a serving or two even when several years old.

I would recommend planting at least 25 crowns per person. If by chance you had extra i"m sure your friends and neighbors would love some fresh asparagus.

When I cut them, do I leave any of the stalk in the ground or cut them to the ground?

Cut them at or just below soil level at an angle with a sharp knife. Rinse and put them in a glass with a few inches of water and store in the fridge and they will stay fresh longer.