With some variation based on latitude and on the variety of poppy, poppies flower during spring and summer. Some poppies flower for only a few days, while others last for weeks.
California poppies grow wild and flower all summer long, but each flower only lasts a few days. Oriental poppies bloom for a very short period during late spring and early summer, with each bloom lasting about one month. Poppy mallows bloom for about ten weeks during the summer. Celandine poppies flower from April to June and are easy to propagate. So-called "super poppies" flower in June, then have a second blooming in August or September.