[2][5] There are two subspecies:[1] Sea wormwood is a herbaceous perennial plant or subshrub growing to 50 cm, which flowers from August to September; it has strongly aromatic pale grey-green to whitish-green foliage, and is wind pollinated.

The leaves are deeply twice pinnatifid, with narrow, linear segments, and, like the whole plant, are covered on both sides with a dense coat of white cottony hairs.

The small, oblong flower heads, each containing three to six tubular florets 1–2 mm diameter, are of a yellowish or brownish tint; they are produced in August and September, and are arranged in racemes, sometimes drooping, sometimes erect.

[2] John Hill said in 1771 of this species: "This is a very noble bitter: its peculiar province is to give an appetite, as that of the Common Wormwood is to assist digestion; the flowery tops and the young shoots possess the virtue: the older Leaves and the Stalk should be thrown away as useless ....

"[9] Thornton, in his Family Herbal, tells us that "beat up with thrice its weight of fine sugar, it is made up into a conserve ordered by the London College, and may be taken where the other preparations disgust too much.