Poppy seeds can lie hidden underground for up to 100 years, but once the soil is disturbed they begin to grow. This is why poppies sprang up on the First World War battlefields in such great numbers.Before the War the soil on these battlefields was not rich enough in lime to maintain large populations of poppies. Blasted houses and walls, together with bones from the dead, added lime and calcium to the soil, producing carpets of poppy flowers.