Faithful for 100 million years: beauty and the beetle

A permanent gallery whose works change themselves daily, seasonally and year by year is an extraordinary concept. A permanent exhibition of rare and sought-after masterpieces from around the world is worthy of pilgrimage. In this context, at the beginning of Spring, a visit to Mount Lofty Botanic Gardens is obligatory. The living collections along Magnolia Gully will convince you that botanic gardens indeed have their own blockbuster exhibitions.

The deciduous pink-flowering tree Magnolia campbellii with its spectacular 30 centimetres wide, waterlily-like, pendulous flowers held against the sky on bare branches provided one of the botanical epiphanies that changed my relationship with the world’s floras. I had begun my career as a botanist totally devoted to the Australian flora the richness of our flora and it’s reconciliation with Australia’s environment was so remarkable, and the beauty and bizarre adaptations of Australia’s charismatic plants so entrancing, that I saw little reason to explore exotic plants (that I largely considered either as weeds or as potentially weedy). However, working in the herbarium in Melbourne I was surrounded by the Royal Botanic Gardens. Unsurprisingly perhaps, I was seduced by the richness of the Gardens’ plant collections, and of course, by the plants themselves; as well as by the scholarship and passion of their curators and their constituencies.

The botanical significance of a range of plants such as Magnolias had been part of my botanical education; prominent in evolution as early flowering plants retaining ancient characteristics. Much of the plant classification I studied at university has been revisited with DNA analysis. These studies confirm Magnolia’s primitiveness, at the same time as changing perceptions of the primitiveness of other plants such as waterlilies. Botanists have also placed related genera that may still be sold in nurseries as Manglietia and Michelia under Magnolia.

The natural distribution of Magnolia in Eastern North America, Eastern Asia, and in the fossil record in Europe, illustrates what seemed to be a strange disjunction in distribution which was observed as early as 1750 by Jona Halenius (or perhaps his teacher Carl Linnaeus). The strange distribution began to be explained a century later as the theory of super-continents emerged, while another century passed before the recognition of continental drift provided further explanation. Halenius’s observation of the botanical links between Eastern North America and Eastern Asia is now interpreted in the context of their ancient connection in the super-continent of Laurasia. Similarly the botanical links between Australia, South America and Africa (and even the fossil record in Antarctica) reflect the ancient connections between these continents through the super-continent of Gondwana.

Magnolia shares an interesting link with the primitive Victoria amazonica (Giant Amazon Water Lily) thar graces Adelaide Botanic Gardens through a shared relationship with a scarab beetle (cyclocephala) that pollinates both the Mexican Magnolia tamaulipana and Victoria amazonica. That relationship seems linked in turn to the plants’ ability to generate heat in the flower to attract the pollinator. This works both by volatilising an attractive scent (at least to a beetle) and providing warmth for the beetle. Heat-generating flowers are surprisingly widespread in primitive flowering plants.

This close relationship between the Magnolia flower and the scarab beetle can be traced to the dawn of the flowering plants in the Cretaceous period (the period following the dinosaur-famous Jurassic period from 145 million years ago). Indeed, the relationship between the water lily Nymphaea lotus (Egyptian White Lotus) and the African scarab beetle (Ruteloryctes) is claimed to represent a faithful relationship for the last 100 million years and the relationship between the Magnolia and the beetle might be from a similar era – impressive fidelity!

The botanical story is a richly layered one; the plants speak eloquently for themselves.

Magnolia grandiflora, the beautiful, hardy, evergreen tree with its tough, glossy, dark green leaves manages well on the Adelaide Plains and is perhaps the best-known species. Some species are tropical, such as Magnolia macrophylla characterised by large white flowers with purple centres and beautiful, almost membranous light green, and as the name suggests, by large leaves to 60 centimetres long. A surprising range of species thrive at Mount Lofty Botanic Garden.

Magnolias are associated with plants like Rhododendrons and Peonies – and of course they can be demanding on the Adelaide Plains. A visit to Mount Lofty Botanic Garden demonstrates the success Hills gardeners can have with these plants. Magnolias prefer a neutral or slightly acid soil and sheltered position with reasonable drainage. They grow well from seed and can also be layered (and layered plants are likely to flower earlier than seed grown plants).

The Magnolia Gully at Mount Lofty Botanic Garden includes around 26 Magnolia species. Magnolia campbellii remains a favourite (although it is unlikely to reach the 40 metres attributed to this species in habitat in Bhutan, there is some vicarious pleasure in knowing that it can). M. denudata’s elegantly-held ivory colour tulip-shaped flowers on bare branches and M. stellata’s star-like flowers exploding like catherine wheels from a small bared shrub are just a few of the delights at Mount Lofty. Several others are already in bloom.

Visiting Magnolia Gully: The Mount Lofty Botanic Garden, best entered from Lampert Road, Piccadilly is open from 8:30am to 4pm weekdays, 10m to 5m weekends and holidays. Magnolia Gully, up a bit of a slope between the entrance and the Lower Carpark, is the best pace to start. A brochure box at the start of the trail outlines some of the treasures of this collection.

Originally published in The Adelaide Review on 1 September 2011.

For more information about the Botanic Gardens of South Australia, visit the website.

@StephenJForbes
@BotGardensSA

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