Plant 125

Adoxa moschatellina L. (Adoxaceae)


Townhall clock

Adoxa moschatellina, a perennial, rhizomatous herb of damp, shaded woodlands and hedgerow bottoms, has a circumboreal distribution being found in disjunct regions of Europe, Asia and North America. Adoxa moschatellina is a spring-flowering species and, by June, at low elevations, the plant has died back.

Despite its wide geographic distribution, Adoxa moschatellina is frequently overlooked, although when spotted it cannot be confused with any other species; the flower heads are distinctive and the leaves are compound, the leaflets arranged in threes. The generic name, meaning 'without glory', is a reference to its obscure habit and flowers, whilst the specific epithet refers to the slight muskiness the plant is meant to have when it is damp.

The radially-symmetrical, hairless flowers are small (c. 6 mm diameter) with greenish-yellow petals. The flowers are arranged at the tips of flowering stalks, in groups of five; four lateral flowers form the faces of a cube, a fifth, terminal flower sits on the top of the others. This floral arrangement gives the plant one of its common names, townhall clock. Within the flower head, the flowers are of two types; the four lateral flowers have five petals and stamens (male parts), the terminal flower has four petals and stamens. Superficially, each flower appears to have twice as many stamens as expected. This is because each stamen is forked, split vertically into two parts. Furthermore, the nectary around the base of the stamens is formed by a ring of multicellular hairs. The flowers of Adoxa moschatellina are probably pollinated by small insects, but few seeds are set each year in Britain. The main means of propagation for the species appears to be vegetative, by the underground rhizomes.

Adoxa moschatellina was considered the sole member of the family Adoxaceae until the early 1980s when two new species, that belonged to the family were discovered in China; one of these species was included a new genus, Sinadoxa. The position of the family in the flowering plant tree of life was equally enigmatic; some authors arguing it was related to the saxifrage family, others that its relative was the ivy family. However, on the basis of morphological and DNA characters the Adoxaceae is clearly related to some members of the traditionally circumscribed honeysuckle family (Caprifoliaceae). The most closely related genera to Adoxa are Sambucus (elders) and Viburnum (viburnums). Today, the family Adoxaceae comprises nearly 250 species in four genera.

Further reading

Eriksson T and Donoghue MJ 1997. Phylogenetic relationships of Sambucus and Adoxa (Adoxoideae, Adoxaceae) based on nuclear ribosomal ITS sequences and preliminary morphological data. Systematic Botany 22: 555-573.

Holmes DS 2005. Sexual reproduction in British populations of Adoxa moschatellina L. Watsonia 25: 265-273.

Stephen Harris