The Eastern exponents Centaurea pannonica / angustifolia of the narrow-leaved knapweed of the Centaurea jacea aggregate are somewhat different of the Western ones ( Centaurea timbalii): The upper leaves of the Western Centaurea timbalii are often only 1 to 2 mm wide, greenish, and the base leaves have often side ruffles. At the Eastern Centaurea pannonica the upper leaves are with 3 to 4 mm somewhat wider, whitish by pilosity, and the base leaves have usually no side ruffles. The flower head of the Eastern Centaurea pannonica is more or less roundish, while that of the Western Centaurea timbalii tends to be of a longish form. But as you can see on the photos the sentences above are indeed describing a tendency, but there are many exceptions from these rules. In Southern Germany, e.g. Baden-Württemberg, Bavaria, and Thuringe, there are transition clans.