Water Spiderwort (Tradescantia fluminensis), a notorious colonist of Melbourne’s creeklines and river valleys. Still known popularly in some quarters as Wandering Jew (also Wandering Trad, Wandering Creeper, etc), it has been sold in Victoria since 1855 in a variegated form (thanks J. and J. Rule, Richmond) and 1886 in the typical form (thanks George Smith of Armstrong Street, Ballarat), principally as a house plant and an ornamental groundcover. The plant appears to have only widely naturalised in Victoria from c. the 1960s, possibly as a consequence of a more widespread adoption of the plant in the post-war period as a desirable groundcover for shady suburban and rural gardens.
Incapable of setting seed in Australia, Water Spiderwort makes up for that deficiency by being an incredibly prolific rooter, able to repropagate from tiny pieces of broken stem and to grow several metres per year. This makes manual control extremely laborious and difficult, a problematic characteristic in a plant that is also resistant to some classes of chemical herbicide. Tradescantia forms dense mats or swards in riparian forest and other damp, shaded sites, to the exclusion of most other herbaceous plants and suppressing recruitment of shrub and tree seedlings.
T. fluminensis is a threat to a number of intact ecologies in both Victoria and NSW, and is a recurring feature of damaged metropolitan sections of the Yarra and its tributaries. In NSW the plant was formerly banned in several eastern council areas, until a review in 2014 determined that its extensive distribution in that state was beyond any feasible human control. Although the legislative environment is different in Victoria, the effective assessment is comparable: barring the introduction of an effective biological control, in just 50-60 years of adventitious growth and accidental distribution this clonal plant has become a permanent fixture of Melbourne’s riparian corridors.