Giesen produces wines from Marlborough, New Zealand's South Island, where cool maritime conditions shape distinctive expressions across multiple varietals. The winery's portfolio spans Riesling, Shiraz, and Sauvignon Blanc, with flagship releases including the Reserve Selection Canterbury Late Harvest Riesling—a dessert wine of concentrated fruit and balance—alongside The Brothers Shiraz, which draws on the region's capacity for structured red wines. The Single Vineyard Fuder Matthews Lane Sauvignon Blanc represents the winery's commitment to site-specific white wine production, a hallmark of Marlborough viticulture. These wines have been assessed by major critics including Wine Spectator, Wine Advocate, Decanter, Wine Enthusiast, and Falstaff, reflecting their standing within the international wine trade.