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.
2007		(con. 1890s) W. Ings ‘A Convenient Exchange’ in Public Space 3 2: The only uphill gardening that old sod will be doing will be in the back of Black Bess.
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 .