Diefenhardt works the steep vineyards of Rheingau, Germany's premier Riesling region, where slate and schist soils shape wines of mineral precision. The winery's portfolio centers on dry expressions—Riesling and Pinot Noir from Martinsthaler sites, alongside Spätburgunder (Pinot Noir's German name) from the Schlenzenberg vineyard. These wines have been assessed by Falstaff, Wine Advocate, Wine Spectator, and Wine Enthusiast. The Martinsthaler Wildsau Pinot Noir Trocken and Martinsthal Schlenzenberg Riesling Trocken represent the winery's core offerings, both dry-styled and rooted in the region's cool-climate character. Rheingau's northerly latitude and river influence produce wines marked by acidity, aromatic intensity, and aging potential—qualities evident in Diefenhardt's approach to both white and red varieties.