Compost
For good germination it’s best to use a specialist seed compost, as these contain finely graded materials for an open, well-drained structure that holds essential moisture and air close to the seed.
These composts contain a minimal amount of plant nutrients: seeds contain their own food, and don’t need much by way of extras. In fact, too rich a compost can cause rotting and inhibit root growth.
Choose from a heavier, loam-based John Innes seed sowing compost or a lighter (ideally peat-free) one.
Incidentally, John Innes isn’t a brand, but a formula for the materials used to make the compost. Look out for the JIMA (John Innes Manufacturer’s Association) seal of approval on the compost bag to ensure the contents are of the highest quality.