The species' bud scales are efarinose, ovate to oblong and are 2–5 centimetres (0.79–1.97 in) long. The leaves form a rosette which have winged petiole that is 1–3 centimetres (0.39–1.18 in) long. It have even longer leaf blade, measuring 2–10 by 2–7 centimetres (0.79 in–3.94 in × 0.79 in–2.76 in), efarinose, puberulous and is ovate to deltoid. The base itself is cordate and subsagittate with irregular margins, coarse dentate and acute apex. P. tanneri have 10–20 centimetres (3.9–7.9 in) long scapes which elongate, 45 centimetres (18 in) long near the fruit part and are farinose toward the apex. Umbels have 1-2 flowers with bracts that are acuminate to subulate and are 5–10 millimetres (0.20–0.39 in) long from the broad base. Pedicel is as farinose as the apex and is 1–3 centimetres (0.39–1.18 in) long. The flowers are heterostylous with tubular to campanulate sepals which are 7–10 millimetres (0.28–0.39 in) long. P. tanneri have an emarginated and lanceolated lobes which are obovate to oblong with a light to deep purple colored corolla which can also be blue or white. Tubes of these species can be 1–3 centimetres (0.39–1.18 in) long while the limb is 2–2.5 centimetres (0.79–0.98 in) wide. Flowers are heterostyly with stamens toward the apex and bloom in May.