slipper orchid vs ladies' slipper

slipper orchid and ladies' slipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
slipper orchid	Yes	No	No	No
ladies' slipper	Yes	No	No	No

As nouns, slipper orchid and ladies' slipper are synonyms defined as:

slipper orchid and ladies' slipper: any of several chiefly American wildflowers having an inflated pouchlike lip; difficult or impossible to cultivate in the garden

Other synonyms of slipper orchid include lady's-slipper, lady's slipper, lady-slipper, lady slipper.

slipper orchid (noun)	ladies' slipper (noun)
any of several chiefly American wildflowers having an inflated pouchlike lip; difficult or impossible to cultivate in the garden	any of several chiefly American wildflowers having an inflated pouchlike lip; difficult or impossible to cultivate in the garden