State Herbarium staff member Chelsea Novice holding a specimen of Sarcothalia radula. Photo: B. Baldock.

DEWNR‘s last Park of the Month for 2016 is Canunda National Park on the South Australia’s south-eastern shore. Fittingly, the State Herbarium has chosen an alga, Sarcothalia radula (Esper) Edyvane & Womersley, as Plant* of the Month (even though technically speaking, red algae are not plants).

[* = and other organisms traditionally studied by botanists]

Bigger and bolder at Canunda

The South East of South Australia − including Canunda N.P. shores − is rich in algal species, particularly red algae. An upwelling of cold, nutrient-rich bottom waters occurs in summer, producing both a large diversity and large sizes of some algae (see Butler et al. 2002, 900kb PDF). For example, the Giant Kelp (Macrocystis pyrifera) and Bull Kelp (Durvillaea potatorum), are common big browns along rocky parts of the Canunda N.P.

But the reds can be big, too.

Sarcothalia radula, base of alga with holdfast. Photo: B. Baldock.

Sarcothalia radula is a bright-red-purple alga looking like a filmy, plastic sheet that reaches 1½ m in height in calm waters. It can be paper-thin, and not surprisingly gets damaged, with holes appearing in the blade. Remarkably for such a large plant, this alga is fixed to rocks at depths of 1-10 m by the tiniest of holdfasts.  How it withstands being swept from its substrate by the surge of water in its habitat is difficult to imagine.

Smaller plants may be lance-shaped, or even appear slashed into narrow strips, possibly a response to depth of water, light and ferocity of waves.

A descriptive common name, giant pimply-sheets, coined in the Algae Revealed fact-sheet  (960kb PDF) on eFloraSA, highlights the strange texture present when a female plant is fertile. Thousands of small, pimply (papillose) bumps on very short stalks are scattered on the surfaces and edges of blades. The common name found on Algae Base, is tongue weed, but fertile female blades must resemble pretty furry tongues when fertile!  In fact, the specific epithet radula, Latin for “rasp” or “scraper” more aptly describes them.

Sarcothalia radula: cross-section through blade (left) and surface view of the “pimply” female blade margin (right). Photos: B. Baldock.

Internally, the microscopic structure of blade cores (image above) shows many-armed cells separated by an extraordinary amount of space. Surface layers consist of compact, outward-facing chains of small cells.

We have some 60 specimens of Sarcothalia radula in the collection of the State Herbarium of South Australia. Globally, the species is found in cold waters across the southern hemisphere.

Perhaps after local storms you may come across this impressive red washed up on Canunda beaches.

Contributed by Carolyn Ricci and Bob Baldock, Phycology Unit, State Herbarium.

Orthrosanthus multiflorus, Kangaroo Is. Photo: D. Armstrong.

As the second Plant of the Month for November 2016, the State Herbarium of South Australia has chosen Orthrosanthus multiflorus Sweet (morning flag). It is a native member of the Iris family (Iridaceae) found in both Parks of the Month, Kelly Hill Conservation Park and Seal Bay Conservation Park.

Plant a flag in your garden!

Morning flag is a hardy tufted perennial that is suitable for cultivation in Adelaide (4.2MB NRM gardening brochure) and elsewhere in temperate S.A., provided frost-prone areas are avoided. For further information see the Botanic Gardens of SA Plant Selector and the State Flora Nursery Catalogue (7.5mb PDF), which happens to feature our Plant of the Month on its front cover!

Within South Australia, morning flag is almost entirely confined to Kangaroo Island, apart from several records on the southern tip of Eyre Peninsula and a questionably native occurrence near Inman Valley on Fleurieu Peninsula. It is the dominant ground cover plant in the Rocky River visitor precinct of Flinders Chase National Park, its tough grass-like leaves being resistant to grazing by kangaroos, wallabies and Cape Barren Geese.

Morning flag at Rocky River, Flinders Chase National Park. Photo: D.N. Kraehenbuehl.

In the South Australian flora, the Iris family (Iridaceae) is dominated by introduced species (currently 52 listed in the Census) and these are largely South African garden escapes. Orthrosanthus multiflorus is one of only three native Iridaceae species found here (the other two being Patersonia species). Have a go at growing it and help redress the imbalance. It would make a wonderful addition to South Australian gardens as an alternative to the many introduced ones!

The delightful illustration below by Edwin Dalton Smith was published with the original description of the species by the English botanist and horticulturalist Robert Sweet in 1827 in his Flora Australasica or a selection of handsome or curious plants native of New Holland and the south sea islands (1827-1828).

Contributed by State Herbarium botanist Peter J. Lang.