Greenspace: A guide to the trees of the Adelaide Plains

On the nature strip outside our house is a fine Western Australian red-flowering gum (Corymbia ficifolia). My guess is it’s about 50 years old but already a venerable specimen yet still vigorous enough to ignore the longicorn beetles that have facilitated the demise of others locally. It likely has its roots in a lense of surface groundwater as it’s a big tree – the canopy stately in dark Hooker’s green (the colour named for the botanist) and spectacular in flower when the corymbs (after which the genus for bloodwoods is named) of spectacular bright orange flowers provide a beacon for nectar and pollen feeders – the canopy bristles with musk and rainbow lorikeets and New Holland honeyeaters. It’s a beautiful tree, visible, publicly owned and enjoyed (and an obvious choice for parking in summer). Red-flowering gums are one of my favourite trees for the Adelaide Plains.

There’s also a lovely hybrid with the swamp bloodwood from the Kimberley – this hybrid includes ‘Summer Beauty’, a pink cultivar, and ‘Summer Red’ that does well here.

At the Royal Show this year I listed another 19 of my favourite trees for Adelaide. There are really no ‘best’ trees here – obviously tree selection depends on the situation and your taste. However, as I’ve previously observed, I’m concerned that tree selection in Adelaide has been driven by concerns about risk and cost rather than by opportunity and benefit.

As a result, big trees such as Moreton Bay figs and even red-flowering gums are less likely to be planted now. The future of big trees in our cities seems uncertain yet their contribution to beauty and utility for sustainable urban environments and healthy people and communities is profound. My list here includes, mostly, big trees that I’d like to see urban planning provide the time and space to establish. Perhaps developers and planners need to adapt Peter Cundall’s description of gardening as ‘controlled patience’ for urban planning.

So, here are the other 19. Note that all of these have succeeded on the Adelaide Plains. An annotated list will have to suffice for now – the story that each of these trees’ merits will have to wait for future editions.

The ombu tree (Phytolacca dioica) develops a massive table-like base on the scale of a Moreton Bay fig. The unofficial national tree of Uruguay, the oldest specimen in Adelaide was planted by John Reynell at the Reynella vineyard in 1841 – there’s another fine specimen perhaps also planted by Reynell in a garden on Robe Terrace.

The narrow-leaved or Queensland bottle tree (Brachychiton rupestris) is becoming more commonly planted in Adelaide. There’s a wonderful tree in the Australian forest border in Adelaide Botanic Garden – although we’re yet to establish anything as bold as the famed bottle tree avenues of Roma.

The silk-floss tree (Ceiba speciosa) is another bottle-shaped tree with large, bright pink flowers and boab-like leaves. Again, there’s a good specimen in the Adelaide Botanic Gardens – the spiny young stems seem to deter planting but the success of these trees in Sicily and California suggests that they’re hardly a dire threat to our safety (although there are spineless forms available).

The final pachycaul (thick trunked) tree here is Grandidier’s baobab (Adansonia grandidieri) – a gargantuan and towering parallel-sided tree in its Madagascan home. The young tree in the Adelaide Botanic Garden has prospered over the past few years. Too early to be convincing but a great start for this species usually considered better suited to Darwin.

The river red gum (Eucalyptus camaldulensis) is a quintessentially South Australian tree (think of Hans Heysen’s depictions and Harold Cazneux’s Spirit of Endurance near Wilpena Pound) disappearing from the Adelaide Plains and requiring our commitment in time and space.

The valley oak (Quercus lobata) is a deciduous American analogue for the river red gum that inhabits similar habitats in western USA – there are some fine specimens at the
Waite Arboretum.

If you are concerned about space, a number of smaller trees native to South Australia’s outback deserve more attention. These include the delightful silver-leaved weeping myall (Acacia pendula), and the fine native willow (Geijera parviflora). Both are occasionally planted as street trees here, and, with remarkable success, in California.

Favourite medium-sized trees include the Irish strawberry tree (Arbutus unedo) and its natural hybrid with the Greek strawberry tree (A. andrachne) – available as A. x andrachnoides, the Mediterranean carob (Ceratonia siliqua) that makes a good hedge (with vigilant pruning) and the native orange or iga warta in the Adnyamathanha language (Capparis mitchellii). These three aren’t properly viewed as domestic fruit trees but do produce a harvestable crop.

The only domestic fruit tree on my list is the black mulberry, a native of south-west Asia that survives with little water in the Flinders Ranges and even in the Anangu Pitjantjatjara Yankunytjatjara Lands. The famed specimen on Reeves Point near Kingscote on Kangaroo Island dates from 1836 – the oldest colonially planted tree in South Australia.

The claret ash (Fraxinus angustifolia ssp. oxycarpa cv. ‘Raywood’), a South Australian icon identified by the National Trust, the Chinese pistachio (Pistacia chinesis), the maidenhair tree (Gingko biloba) and the Euphrates poplar (Populus euphratica) are excellent medium-sized (on the Adelaide Plains) deciduous ornamental trees (the latter you can see on the main lake at Adelaide Botanic Garden). For an evergreen shade tree the cork oak (Quercus suber) is excellent although ultimately a large tree (visit Rockford Estate or Norwood Coles’ carpark).

My final choices are the stoic mulga (Acacia aneura) and the heroic waddy wood (A. peuce) – for their totemic meaning in South Australia’s landscape and Aboriginal cultural heritage ahead of their success in cultivation here.

Two eucalypts and three acacias in a list of 20? Well, I’d love to see other people’s lists – deciding what to leave out is, as always, harder than deciding what to include.