Complex sentence: Poppy seeds and fixed oils can also be nonnarcotic because when they are harvested the morphine practically disappears from the seeds twenty days after the flower has opened (Jonsson and Krzymanski, 1989).
Split into simpler sentences: Poppy seeds and fixed oils can also be nonnarcotic because when they are harvested. The morphine practically disappears from the seeds twenty days after the flower has opened (Jonsson and Krzymanski, 1989).