The RHS has a database of plants on its website. For astrantia it says moist but well-drained soil if in full sun or well-drained in partial shade.https://www.rhs.org.uk/Plants/1870/Astrantia-major/Details
Thank you for the link Obelixx. This is from their printed version 2010: "Genus of perennials, widely used in flower arrangements. Fully hardy. Requires sun or semi-shade and well-drained soil. Propagate by division in spring or by seed when fresh, in late summer."I guess the website is more up to date.