Green’s Dictionary of Slang

cabbage patch n.1

also cabbage-field
[pun on greens n.1 (1)]

the vagina.

[UK]Farmer & Henley Sl. and Its Analogues.
[UK]A. Crowley Snowdrops from a Curate’s Garden 25: Gertie and Herminia seized each one of his shoulderblades in their gaping cabbage-fields.
[US]Maledicta IV:2 (Winter) 193: The third and most numerous group of fruit and vegetable synonyms comes from analogy with the corresponding feminine terms, so that the gardener tends the garden or cabbage patch.