Q.How do I know when to pick my artichokes
My plant is very big with 1/2 dozen artichokes ranging in different sizes. Small or big are all opening and turning purple.
Different sizes of artichokes will grow on the same plant - this is normal. Usually the ones on the very top and center are biggest and get smaller the lower they are on the plant. They all need to be harvested before the blossoms open, regardless of their size. This article will help you determine when to harvest your artichokes:
https://www.gardeningknowhow.com/edible/vegetables/artichoke/how-to-harvest-artichokes.htm