The Dwarf Elder is a small (rarely above 3ft in height) hairless perennial which can be identified by its simple straight stems which are less woody than those of the Elder and an unpleasant smell. The leaves are more numerous than on the common Elder and are toothed and the flowers which appear between June and August can be white or pink, forming in domed clusters smelling of bitter almonds. The fruit ripens to a shiny black colour. The Dwarf Elder favours damp woodland margins and clearings. Medicinal uses include as a diuretic and to reduce fluid retention. The name Dwarf Elder refers to a completely different plant in the USA

Old names for Dwarf Elder include Danewort and Walewort (wal-slaughter) are  traceable to an old belief that it sprang from the blood of slain Danes - it grows near Slaughterford in Wilts, that being the site of a great Danish battle. Others suggest that it was brought to England by the Danes and planted on the battlefields and graves of their slain countrymen. In Norfolk it is still known by the name of Danewort and Blood Hilder (Blood Elder).

What Culpepper says

THE DWARF-ELDER

Description. This is but an herb, every year dying with his stalks to the ground, and rising fresh every spring, and is like unto the elder both in form and quality, rising up with a square rough hairy stalk, four feet high, or more sometimes. The winged leaves are somewhat narrower than the elder, but else like them. The flowers are white with a dash of purple, standing in umbels, very like the elder also, but more sweet in scent, after which come small blackish berries, full of juice while they are fresh, wherein is small hard kernels, or seed, the root doth creep under the upper crust of the ground, springing in divers places, being of the bigness of one's finger or thumb sometimes.

Place. The elder-tree groweth in hedges, being planted there to strengthen the fences and partitions of ground, and to hold the banks by ditches and water-courses.

The dwarf elder tree, growing wild in many places of England, where being once gotten into a ground, it is not easily gotten forth again.

Time. Most of the elder trees flower in June, and their fruit is ripe for the most part in August. But the dwarf-elder, or wall wort, flowereth somewhat later, and his fruit is not ripe until September.

Government and virtues. Both the elder and dwarf tree are under the dominion of Venus. The first shoots of the common elder boiled like asparagus, and the young leaves and stalks boiled in fat broth, doth mightily carry forth phlegm and choler. The middle or inward bark boiled in water, and given in drink, worketh much more violently; and the berries, either green or dry expel the same humour, and are often given with good success to help the dropsy; the bark of the root boiled in wine, or the juice thereof drank, worketh the same effects, but more powerfully than either the leaves or fruit. The juice of the root taken, doth mightily procure vomitings, and purgeth the watery humours of the dropsy. The decoction of the root taken, cureth the biting of an adder, and biting of mad dogs. It mollifieth the hardness of the mother, if women sit thereon, and openeth their veins, and bringeth down their courses: The berries boiled in wine performeth the same effect; and the hair of the head washed therewith is made black. The juice of the green leaves applied to the hot inflammations of the eyes assuageth them; the juice of the leaves snuffed up into the nostrils, purgeth the tunicles of the brain; the juice of the berries boiled with honey, and dropped into the ears, helpeth the pains of them; the decoction of the berries in wine being drank provoketh urine: the distilled water, of the flowers is of much use to clean the skin from sun-burning, freckles, morphew, or the like; and taketh away the head-ach, coming of a cold cause, the head being bathed therewith. The leaves or flowers distilled in the month of May, and the legs often washed with the said distilled water, it taketh away the ulcers and sores of them. The eyes washed therewith, it taketh away the redness and bloodshot; and the hands washed morning and evening therewith, helpeth the palsy, and shaking of them.

The dwarf elder is more powerful than the common elder in opening and purging choler, phlegm, and water; in helping the gout, piles, and women's diseases, coloureth the hair black, helpeth the inflammations of the eyes, and pains in the ears, the biting of serpents, or mad dogs, burnings and scaldings, the wind cholic, cholic and stone, the difficulty of urine, the cure of old sores and fistulous ulcers. Either leaves or bark of elder, stripped upwards as you gather it, causeth vomiting. Also Dr. Butler, in a manuscript of his, commends dwarf elder to the sky for dropsies, viz to drink it, being boiled in white wine; to drink the decoction I mean, not the elder.