Notice the round ends on this young spinach. If you look very carefully, you can see some of the narrow second leaves at the sides of the plants. When the spinach matures, the main leaves will develop pointed ends, like the spinach which was wintered over. This photo is from late May, and the spring sown plants will be harvested through the month of June, when hot weather will make them a little bitter, and then they will 'bolt' or go to seed.