Can they be planted in cycles to have blooms for a longer period of the summer. With stratification before planting each time.
Thank you for contacting the Toronto Master Gardeners.
Papaver somniferum is an annual which can grow up to 100cm tall. Poppies grow best in full sun- on well-drained, fertile soil. In general, poppies do not like to be transplanted and as a result, direct sowing is the prefered method for propagation. Poppies flower from April-July. Seeds can be sown in April when the soil has warmed up for a late in the season flower or you can sow the seeds in the fall for early flowering.
If you decide to use transplants “germinate and grow plants at 60°F. Grow seedlings for 4-6 weeks and plant out around the last frost date for the area. Transplant carefully to minimize damage the roots while planting.” Refer to Seed Popy In the Garden Utah State University
Lastly, we have received numerous inquires concerning the sowing of poppy seeds. For a number of our archived posts simply type “poppy seeds” in the Find It Here bar located to the right of the page. The following information is from a few of these archived posts:
Annual – these are easy to grow, and because the seeds are so small, a trick for planting is to mix them with sand, for a better distribution. Since you say you are moving to southern Ontario, the timing for sowing is late winter, February or March. Mark the spot! The feathery foliage sprouting from the ground in spring are poppies: don’t weed them out. If you continually sow through the spring, you can get a much longer period of bloom. If you get to southern Ontario too late in the spring, don’t worry, they can be sown in September to October, for the following spring.
Although poppies adapt to all climate zones, you may need to experiment to find the right time to plant the variety you have on hand. The best time to plant is when the poppies have fully gone to seed (and would self-seed themselves – according to Mother Nature’s timetable) – this could be in the early fall or early spring.
In some cases, either of these times may work. If you don’t know when your poppies would self-seed, you can experiment by sowing some seeds in July, as some plants may germinate next spring, and some of the seeds in the fall. Save half the seeds in the refrigerator to plant the next spring, once the soil becomes workable.
Prepare the ground by putting compost or soil over the surface, and working it in lightly. The poppy seeds are so tiny, it’s best to just sprinkle them lightly over the surface of the soil (you can mix them with sand to make this easier) and tamp the soil down over them a bit with your hands. Don’t bury them, as they need some sunlight. Make sure the seeds scatter nicely so they don’t end up in clumps, as the emerging seedlings would crowd each other and have to compete and, so would not grow large.
Remember that poppies don’t like to be transplanted, so moving them as they emerge is not an option. The flowers should come up in the spring when the soil warms up and will reseed themselves each year. You should not have to plant the poppies again. If the seed you sow in spring does not germinate after a few weeks, fork the ground over gently to bring the seeds to the surface – the sunlight might help to trigger them to germinate.
Here’s a good overview of how to sow poppy seeds (note that many gardening sites mention spring and/or fall sowing):
Colorado State University – Extension2003: The Year of the Poppy” https://www.coopext.colostate.edu/4dmg/Whats/2003popy.htm
If you prefer to sow the seeds yourself as opposed to leaving the plants to self-seed, harvest the seeds when the weather is dry (the seeds should be dry and rattling inside the pods). In Ontario’s climate, it is recommended to sow the seeds in very early spring [they need freeze/thaw conditions in order to germinate], and covered with a thin layer of soil (they need sunlight to germinate). Keep the seedbed moist until tiny plants emerge (usually from 7-28 days – this depends on the temperature of the soil) – note that the plants do tolerate frost. The plants should flower in late spring or early summer and seed pods will mature about 80-90 days following planting – ready for the next harvest.