This article summarizes information on the taxonomy of 'Appar', a perennial blue flax cultivar (Linum perenne L. [Linaceae]), and characteristics that distinguish it from native Lewis flax (Linum lewisii Pursh [Linaceae]). 'Appar' apparently originated as a European flax that escaped from garden cultivation. Randomly amplified polymorphic DNA (RAPD) analysis places 'Appar' with other collections of European Linum perenne and separates it from native North American collections of Lewis flax. Morphologically, 'Appar' differs from Lewis flax in having an intense blue petal color, shorter internodes, leaves that point upward along the stem, and multiple slender stems suffused with red near the base. The heterostylous reproductive system, which it shares with its European cousins, keeps 'Appar' reproductively isolated from native populations of Lewis flax. All available data indicate that 'Appar' is not invasive and does not pose a threat to native flax populations. Ease of establishment, seed production, and showiness of the abundant flowers recommend 'Appar' for use in xeriscape plantings. Alternatively, the recent germplasm release of Lewis flax, 'Maple Grove', also establishes readily from seed and can be effectively used when objectives dictate the exclusive use of native germplasms.