As the two remnant trees on our farm, River red gums (Eucalyptus camaldulensis) hold a special place in our hearts. Our red gums are bent and stretch up the hillside away from the prevailing winds. Red gums are not unique to the Fleurieu however, in fact, their high level of adaptability means that they have a distribution across Australia, most commonly occurring on floodplains and waterways as well as throughout higher rainfall regions.
With red gums as a significant species in the past ecosystem of our property, they’ve been a clear choice for revegetation. When planting, we’re constantly inspired by their resilience. I’ve heard it said that red gum roots grow at a centimetre a day, which puts them at over three-and-a-half metres a year. If it’s true, then it’s an indicator of their startling ability to find water and nutrients. We’ve been amazed by some of our red gums that have shot to almost 1.5 metres after a couple of years in the ground, but also by their apparent capacity for dormancy. Some seedlings will sit in dry, cracked clay soil for months on end, leaves green but not growing. Then, with a decent rain, they burst into new growth. Likewise, others appear to have died, leaving nothing but a dry stick until the opening rains of autumn when they reshoot from the ground, sending out a profusion of leaves and spindly branches. We’ve noticed some other plants behave similarly – the occasional melaleuca or acacia for example – but none so consistently and successfully resurrect themselves as the red gum.
While I’m still learning my eucalyptus ID, I identify red gums first by their bark, typically rough near the base of the tree, then smooth and dappled white, cream or grey higher up. Red gum buds are also distinctive, with pointed caps in clusters of up to 12. They tend to flower every couple of summers, with the tree abuzz with foraging bees.
At primary school in about Year 3 or 4, I remember drawing a meticulous diagram of a river red gum, labelling all of the ecological services they provide. Reaching to 40 metres in height, they can be the literal giants of an ecosystem, forming the upper canopy that provides protection for the life below. When flowering, they provide nectar and pollen for insects, birds and mammals, while their fruits are relished by birds seeking to feast on ripe seed. The more ancient will have hollows for the nesting sites of birds and mammals, while the leaves also provide a food source, both on their own and as a host for lerps that provide further food for insectivorous birds.
The ecological value of the River red gum is echoed in the many ways it was utilised by Aboriginal people, including the Kaurna traditional custodians of the Adelaide Plains and western Fleurieu Peninsula. According to the Kaurna Seasonal Trail resource, the red gum’s role as nesting site for possums and birds provided a food source for hunters, as well as skins and feathers for clothing. Native bees would also build hives in the hollows, offering honey. Edible grubs live under the bark and around the roots, while the lerps that live on gum leaves also provided a sweet snack. Along the Murray River in particular, Aboriginal groups would strip large portions of bark from the tree to construct canoes, with the resulting scar still visible on many old trees. On the Adelaide Plains, the bark was used by the Kaurna to craft their distinctive shields. Apparently the ‘seed vessel’ could also be eaten, after being soaked.
Seed collection and propagation is relatively straight forward. According to Neville Bonney, when the valves on the maturing fruit go from green to brownish red, the seed is ready for collection. Trim off small branchlets with mature fruit and leave in a warm place for the fine seed to release (I usually leave them on an oven-tray in a warm, sheltered spot). Seed can be sown in tubes in early summer, sprinkled over moist soil.
References and Further Reading
Aboriginal Community College Inc. 1985, The Kaurna Seasonal Trail Excursion Teacher’s Handbook, Aboriginal Community College, Port Adelaide
Berkinshaw, T 2009, Mangroves to Mallee: the complete guide to the vegetation of temperate South Australia, Greening Australia (South Australia), Pasadena
Bonney, N 2003, What Seed is That? A guide to the identification, collection, germination and establishment of native plant species for central southern Australian landscapes, Neville Bonney, Tantanoola