cowslip

As nouns the difference between mayflower and cowslip

is that mayflower is any of several plants that flower in may - especially the hawthorn (in britain) and the trailing arbutus (in the us) while cowslip is a low-growing plant, , with yellow flowers.

As a noun cowslip is

a low-growing plant, , with yellow flowers.

As nouns the difference between cowslip and oxlip

is that cowslip is a low-growing plant, species: Primula veris, with yellow flowers while oxlip is the plant species: Primula elatior, similar to cowslip but with larger, pale yellow flowers.