Four o’clock flower (Mirabilis jalapa), a cultivated pre-contact plant of Central America that became a minor pan-tropical weed and garden escape worldwide following its adoption into European networks of botanical trade.
Grown in Adelaide at least from 1840 if not earlier, and distributed in Melbourne from 1855 at the latest, the ‘Marvel of Peru’ was among the first tranche of ornamental imports in south-eastern Australia, a bulletproof cottage specimen that by the 1880s was so common and easily grown that it was described in the Adelaide Observer as ‘too vulgar to be tolerated in a genteel garden’ (15/09/1883).
M. jalapa is highly adapted to be locally weedy under conditions of cultivation, being self-fertile and with an active rhizome that suckers freely. At the same time, its capability to establish itself ecologically is constrained: it does not encourage the insect pollinators to which the genus is otherwise adapted (hawkmoths, see Cruden 1973) and so does not diversify or adapt readily to new environments; it also produces few seeds and lacks the affinities that would promote seed distribution beyond the limited radius into which they may directly fall.
Consequently, in Australia the plant tends to form short-lived weedy micro-thickets, small centres of localised, subterranean infestation. In Victoria, these have apparently been further limited by the plant’s frost-susceptibility, so that in the past the plant has rarely spread beyond adjacent boulevard strips and fencelines. It is a more common bushland find in QLD and NSW, where something about its climate and soil requirements or the local patterns of garden maintenance have made the plant only relatively more successful. However, in context of changing climatic conditions we should be conscious that some of the conditions that have so far prevented Mirabilis from achieving more than a ‘sparing’ or ‘questionable’ naturalisation in both environmental and urban contexts may not endure.
The photographed plants were found at several discrete sites in Northcote, including boulevards, fencelines and an area of railway margin.