This is a perennial plant, overwintering as a rhizome with buds close to the ground and protected by fallen leaves and withered vegetation.

The stems are upright and sharply square in cross section.

Leaves are oval and pointed, tapering towards the basal leaf stalk and arranged in opposite pairs. The margins are coarsely toothed.

Flowers have a female phase when the stigma is receptive and a male phase a few days later when the anthers ripen. This discourages self pollination. Pollinating insects are bees and wasps.

After flowering there is a period of vegetative reproduction by means of the spreading rhizome so these plants are often found in clumps.

The seed capsule is egg-shaped and splits when ripe to release many tiny dry seeds.

These plants are biennial, overwintering in the leafy stage and flowering only in the second season, after which the plant will die.

They are very conspicuous on account of their tall spikes of large,dense, yellow flowers and many leaves, becoming larger towards the base. The basal leaves have stalks but the upper leaves clasp the stems extensively and nearer the top they become shorter and almost triangular with a slender pointed tip. All leaves are softly felty to the touch.

The flowers have a flat open shape when in full bloom, 3-5 cm in diameter with 3 distinctly hairy stamens above and 2 smooth stamens below as well as a single club-shaped style. The arrangement of flower parts shows a bilateral symmetry making its links to the figwort family more understandable at the visual level.

This is a biennial plant, flowering in its second year and dying back after seeding. It is one of several species of tall Mulleins with soft felted or woolly leaves. This one is distinguishable by the way the main spike produces 4-9 side branches of flowering spikes. It is very similar to Verbascum thapsus, including the existence of stem flaps or frills formed of extensions of the clasping leaves in the mid to upper part of the vertical stem. These extensions run vertically down the stems, often as far as the leaf below. Differences are minimal at the level the casual botanist can appreciate and include the basal leaves which also clasp the stem (V. thapsus has basal leaves with short stalks) and the distinctly notched edges of the leaves (absent in V. thapsus).

The leaf margins are slightly lobed or toothed and the surfaces beneath the thick fuzzy hairs are wrinkled. This and the dense hairy growth are efficient means of reducing water loss by evaporation so enabling the plants to survive in very dry conditions. Even the vertical flap extensions of the leaves along the stem help as they trap rain or dew and channel it down towards the root.

The flowers have petals joined at the base, wide open and slightly funnelled. The hairiness of the three upper stamens is thought to be a pollen trap, luring insects even when no pollen is actually being released. Pollen is only released the morning until about 10am. Insects are also attracted by the high UV reflectivity of the petals.

Each plant has about 200 flowers and they produce together approximately 60,000 tiny seeds that are dispersed by animals and wind.