n. Gardening that takes places in hostile or difficult conditions.
2001
Gardening has long enjoyed the reputation as the most leisurely of leisure activities, a gentle hobby that produces beauty, serenity and compost. And so it may be in the pages of some long-ago seed catalog, but in real life — or its frequent usurper, the Internet — a hardy gardening counterculture has taken root. The 'extreme gardening' its adherents practice includes cultivation in severe conditions as well as some social and aesthetic affinities that make high-altitude subzero planting seem tame by comparison.
1996 (earliest)
If the latest bumper crop of newspaper and magazine articles and TV programs is any indication, boomers are set to become a generation of gardeners in their middle age. … And besides, the sheer mass of this monster-size generation makes it possible to cultivate thoughts of trends in the making: empty-nesters not moving into gardenless condos but staying in their big, old houses to toil in the soil; new meaning for the greenhouse effect; gardening injuries, a whole new field of medicine; … and extreme gardening.
The use of the adjective extreme has gone from teenspeak to cult status (the X Games) to advertising buzzword ("Right Guard: extreme protection"). Now, with the oxymoronic extreme gardening, it looks like this sense of extreme has just about come to the end of its lexical shelf life.