Poppies can be very easy to grow if you follow a few pointers, as perennial poppies like P. bracteatum and P. oriental are robust and just about indestructible, the annual P. somniferum can be very fragile and a little more demanding.
They are two good times of the year to sow poppy seeds, after September to the end of October, this only work if you receive mind winters. Poppies are frost hardy to a certain degree, but if they receive hard frost after frost week after week, they will perish. That said if you can manage to over winter them, autumn sown plants make way bigger and better plants than spring sown ones. Late winter to late spring are the next best times, I start on the first of March and sow until the end of May. Different verities of P. somniferum respond differently to later sowing, all poppies aim to flower around the longest month of the year, so the later you leave the sowing, the smaller your plants will be, the most sensitive verities are the Pink & White and Indian types, these really do need to be sown early, I have sown Pink & White and Indian poppies in June and they grow no more than 6” high, which were very disappointing.
Poppies are best grown outside in situ; they need a rich neutral to slightly alkaline soil to do best and absolutely resent root disturbance. Select a weed free patch of soil in full to part shade, all poppy seeds need to be surface sown; this means that they need to be in contact with the moist soil and be still in sight of the light, the seeds need only need to be pressed into the soil, not buried. Germination will only take place if the temperature rises above 15°C, keep moist and weed free, and protect the small seedling from slugs and birds.
Once the seedlings have reached 1 – 2” in height, they need thinning, again this will depend on the verity of poppy you grow, for example Bush poppies can be spaced 2’ apart and Pink & White and Pharma type can be spaced 4 – 6” apart, the general rule is the closer the plants the taller and weedier they will be. Water regularly, keep weed free and protect the lager plants from strong winds, gales will rip your poppies to bits and snap off lager plants at ground level just before they flower, this is practically depressing.