Tree Aeonium (Aeonium arboreum), a Canary Islands native widely adopted into horticultural use and available in Melbourne from at least the 1850s.
Aeonium is inherent to what the critic might call Melbourne’s ‘vulgar’ residential flora. It is a branching succulent reproducible indefinitely by cuttings, and as pervasive as Northcote bricks. Melbourne’s unkillable ‘rose’ is also frequently unwanted, and a regular guilty fly-tip.
In New Zealand, Aeonium arboreum has proven capable of reproducing both vegetatively and by seed, and has naturalised (c. 1959) on coastal and inland outcrops on both islands. A relatively large number of SA records have also been made since the 1980s.
In Victoria, the plant is known from a few discrete colonies, typically in coastal or near-coastal scenarios protected from frost and with sufficient winter moisture and access to marginal exposed soils (dunes or cliffs) that do not support cover by anything more vigorous. After arising vegetatively from dumped or eroded garden debris, the question of whether these colonies subsequently expand by localised seed dispersal has probably not been investigated here. The flowers have broad pollinator compatibility, but produced seeds may not be well suited to long-distance dispersal, keeping colonies local and presenting an obstacle to achieving a more broadly naturalised ecology.
Recorded occurrences include dune colonies at Barwon Heads and Breamlea to the west of Port Phillip Bay, and Cape Patterson to the east. There is also an unrecorded colony established on cliff face below the fort at Queenscliffe. In Melbourne, Tree Aeonium colonies have been recorded on steep riverbank at Maribyrnong and on Edgars Creek in Reservoir.
The photographed plants form a dense, unrecorded occurrence on a steep exposure to the Ivanhoe side of Darebin Creek. The same cliff face hosts other adventive ornamentals including Narcissus, Geranium and two other succulents, as well as the population of Climbing Groundsel profiled a few weeks ago.