Green’s Dictionary of Slang

a male homosexual; thus uphill gardening, homosexual anal intercourse.

1989		J. Morton Lowspeak 143: Uphill gardening – anal intercourse.
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: uphill gardener euph. He who hoes on the pink allotments; the pusher of a cheesey wheelbarrow (qv) up the kak canyon; a male homosexual.
2000		Guardian G2 16 Feb. 22: I’m an uphill gardener! I dine at the downstairs restaurant!
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 196/2: uphill gardener n. a homosexual.
2010		(con. 17C) W. Ings ‘Trolling the Beat to Working the Soob’ in Int’l Jrnl Lexicog. 23:1 62: In New Zealand an active homosexual might be referred to as an uphill gardener .