The Great Southern region around Albany rewards a few extra days. Two national parks are within an hour's drive and together make Albany one of the best bases for wildflower walking in Australia.
Stirling Range National Park (80km north) is the only place in southwestern Australia where alpine-style plants grow. The jagged peaks rise abruptly from flat farmland; Bluff Knoll (1,095m) is the highest point in southern WA and a genuine mountain walk with scrambling near the top. On clear winter days the summit is cold enough to see your breath. The wildflower season runs roughly August to November.
Porongurup National Park (48km north) is a gentler proposition — ancient granite domes rising through karri forest, with the Castle Rock and Tree in the Rock walks among the most enjoyable in the region. The Porongurup Range is one of the oldest landforms on earth, at around 1.2 billion years. The towns of Porongurup and Mount Barker nearby have good wineries worth visiting on the way back.
The Great Southern wine region spreads across the hills between Albany and the Stirling Range. Riesling and Shiraz are the standouts, and dozens of cellar doors operate within a day-loop drive. Mount Barker is a useful hub; the drive through the hills in autumn is worth doing for its own sake.