At this latitude, almost the whole of the southwest corner of Tasmania is wilderness in the strict sense: no towns, almost no roads, and a climate that comes straight from the Southern Ocean. The Tasmanian Wilderness World Heritage Area covers a fifth of the island and includes button-grass plains, glacier-carved valleys, rainforest and the long white quartzite ranges.
You do not ride into this country so much as up to the edge of it. The Southwest National Park is mostly reachable on foot, by boat or by light aircraft, and the roads that come nearest, the one down the Huon to Cockle Creek and the Gordon River road in the west, both end a long way from Hobart. The surface is mostly sealed, with winding sections through the Huon Valley, apple country, and tall forest of eucalypts such as swamp gum, among the tallest flowering trees on earth.
The weather is the main character. Tasmania's west and south get the Roaring Forties, and rain, wind and sudden cold can arrive on any day of the year. A clear morning can be followed by hail by lunchtime. Pack proper waterproofs and warm layers even in summer, and give yourself time, because roads here are twisty and slow. Wildlife on the road is real: wallabies, pademelons and wombats come out at dusk, and the Tasmanian devil, once common, is now rare enough that seeing one is an event. Slow down at the edges of the day.
Fuel is the thing you must plan. Do not assume anything in the wilderness itself, and the roads that approach it are far from this exact point. Huonville and Geeveston, in the Huon Valley, are the larger stops on the way south, and you should fill up before heading to the end of the road. Some people also carry a spare bottle of water and a snack. The Huon and the D'Entrecasteaux Channel are also known for fresh seafood, particularly salmon, scallops and oysters, so a late lunch at one of the waterside places is a good idea. Summer, from December to February, gives the longest days and the most stable weather, though stable is relative. The reward is a view across a huge, empty, deeply green landscape.