Cowslip (Primula veris) bears upright stems of bright yellow, nodding flowers in spring. It used to grow wild in fields in Britain, though it’s not commonly seen there now. In fact, it’s quite rare in the wild due to over-picking (it’s a medicinal plant) and extensive farming.
Seed can be sown now, but stratify at 4degC for three weeks before planting. Cowslip grows in average to heavy soils in part shade.
Seeds are available from Kings Seeds.