This year I planted Cosmos and Poppys for the first time - from shop-bought seed. I want to harvest the seeds for next year. when do I do this? must the heads dry out first, or do I pick them while they are green? Please advise, thanks.
Cosmos and poppies are great plants from which to collect seeds as they are quite prolific self-seeders. However, both will flower right up until the first frosts if you dead-head them to prevent them from setting seed so the best thing is to do both. Dead-head most of your plants to prolong your display this year and allow a few to produce seed heads. That way you get a longer flowering season this year and the benefit of seeds for next year.
You should wait until the seed heads have matured before collecting seeds – the heads turn brown and, in the case of poppies, you can hear the seeds rattling around inside the pods. Pick a dry, sunny day to harvest your seeds and simply turn the heads into a brown paper bag and give them a good shake. If the seeds come loose, then they’re ready. If you think you need to, spread the seeds out on paper and leave to ensure they are completely dry before storing them. Store your seeds in a paper bag in a cool, dry place until you’re ready to plant in spring.
Both cosmos and poppies will self-seed so, if you leave a few seed heads on the plants, they will ‘explode’ and distribute their seeds on the breeze. These seeds will wait around in the soil over winter and you should see new plants appearing in your garden in the spring - only perhaps not where you want them to be!
A word of caution for collecting seeds of other shop-bought annuals. Don’t try to collect seeds from plants labeled F1 hybrids. These plants won’t come true - in other words, they won’t be the same as the original plant.
