Harvest the flower stems at the base of the stalk, close to the crown, when the flowers are still in bud and just starting to open. Bring them inside to display in vases.
Snip off dying California poppy flowers before they go to seed to keep the plants producing and flowering all summer.
Allow the California poppies to form seed heads toward the end of the season. Do not cut them off. Letting seed heads form encourages California poppies to self-seed. The seeds will sprout the following spring, growing into new plants. California seed heads are rectangular-shaped with pointed tips. They look like elongated cones.