Iowa crab apple vs crabapple

Iowa crab apple and crabapple both are nouns.

Word	Noun	Adjective	Verb	Adverb
Iowa crab apple	Yes	No	No	No
crabapple	Yes	No	No	No

As nouns, crabapple is a hypernym of Iowa crab apple; that is, crabapple is a word with a broader meaning than Iowa crab apple:

Iowa crab apple: wild crab apple of western United States with fragrant pink flowers
crabapple: any of numerous wild apple trees usually with small acidic fruit

Other hypernyms of Iowa crab apple include crab apple, wild apple.

Iowa crab apple (noun)	crabapple (noun)
wild crab apple of western United States with fragrant pink flowers	small sour apple; suitable for preserving
	any of numerous wild apple trees usually with small acidic fruit
	any of numerous varieties of crab apples cultivated for their small acidic (usually bright red) fruit used for preserves or as ornamentals for their blossoms