If foxgloves are allowed to develop and drop seeds, they will self-propagate. However, if you want to propagate a foxglove manually, collect the seeds from spent flowers and keep them in a paper bag until you want to use them. Plant the seeds in the summer, when temperatures are warm, as the seeds require heat to germinate. You can plant foxglove seeds directly into moist soil or start them in a seedling tray before transferring them to your garden.