Posted: 25/03/2015 at 21:49
Judging by search results, mostly "German."
Judging by English search results that aren't about women's fragrances, soil-based, slightly acidic, possibly mixed with a bit of sand to improve drainage:
Crocus says "moderately fertile, well-drained, humus-rich soil"
Van Meuwen are more helpful: "Grow Daphne shrubs in moist, fertile, well drained soil that is rich in organic matter. Choose a position in sun or semi shade. When growing in containers use a soil based compost such as John Innes No. 3."
The Telegraph's site is a clone of Crocus. Kind of obvious when you do this search.
Wyevale Garden Centres say: "NEW WEBSITE COMING SOON! Sign up here to get spammed with emails about it forever!" Well then, sod Wyevale.
Tesselaar have a little more info: "Performs well in a range of soil types, but prefers slightly acidic soils; avoid very heavy water logged conditions."
Finally, because copy-pasting from their site makes a mess of the text-entry box here,
Plantmark say: "Soil Type: Loam, Sandy, Well Drained"
Edit: Hey, something learned: posting and then editing the post tidies up that mess.