DEAL ISLAND FLORA   By David and Trauti Reynolds
Deal island coastal view

Some History of Deal Island in the Kent Group National Park.

The Kent Group of islands was discovered by Matthew Flinders in 1789. He and George Bass sailed past again in the next year during their circumnavigation of Tasmania.  Bass seems to have been rather unimpressed with Deal Island. His journal reads…

‘This small group  (of islands) appears to be formed of granite, which is imperfectly concealed by long straggling brush, and some few still diminutive trees, and seems cursed with a sterility that might safely bid defiance to Chinese industry itself.  Nature is either working very slowly with those islands, or has ceased to work on them, since a more wild deserted place is not easily to be met with. Even the birds seemed not to frequent them in their usual numbers.’

Despite this impression, nature has indeed been busy on Deal.  During the last ice age, the sea level was lower and there was a bridge of land linking Tasmania to the mainland, with the Bass Strait islands like Deal being hills or mountains on that piece of land. Then, somewhere around 10,000 years ago, some of the polar ice melted and the land bridge was flooded. This left the vegetation on the island living in isolation.  There is the potential that over that period changes occurred – so that some plants may now be different to their counterparts in Tasmania and the mainland.

Humans have had an effect too.  There are traces left - on some of the islands – of aboriginal inhabitation. Since Europeans first came here, much has changed.  The advent of sealers probably coincided with an increase in fire frequency on the island.  Since the lighthouse was built in 1846 there have been grazing animals on the island, with associated pasture improvement, and also weeds brought in with feed.  Of all the different plants recorded on Deal, about a third are introduced. Another factor which affects the vegetation is soil type. There are two general types of soil on Deal – that derived from limestone is richer and less acidic than the soil derived from the granite.

On a visit to Deal Island you would find….

Casuarina woodlands (covers 25% of the island)
As you walk through the casuarina woodland, one thing which immediately strikes you is how few other plants occur under the casuarinas. In many cases there are just the casuarina  (Allocasuarina verticillata) trees, which often grow very closely together, and the ground is covered by their needles. In some places there are isolated eucalypts, or groups of them, which break the monotony of the ‘monoculture’ of the rest of the woodland. These trees are probably older than the casuarinas, having survived the most recent fire – after which the casuarinas grew from seed. Other plant types, such as tea-trees (Leptospermum laevigatum), kunzea (Kunzea ambigua), swamp paperbark (Melaleuca ericifolia) and occasionally oyster bay pine ( Callitris rhomboidea) can be found growing with casuarinas. Where the casuarina woodland is close to the coast, some of the more coastal plants will also be found in its margins.

Melaleuca ericifolia
Melaleuca ericafolia
Kunzea ambigua
Kunzea ambigua

Eucalypt woodlands and shrublands (covers 48 % of the island, most common on granite soils and rock)

Eucalyptus nitida (otherwise known as Smithton peppermint) seems to be the only type of eucalypt growing on Deal. You might find it in a protected gully surrounded by casuarinas (Allocasuarina verticillata).  Here it is in good moist soil, has been protected from fire and the drying winds. It is a tall, straight, single stemmed tree. On the other hand, growing on bare granite, with little soil and subject to fires, it will have a multi stemmed mallee form and will be able to grow more stems from a tuber at it’s base.
The eucalypt forests are much more open than the casuarina forest.  This allows other types of plants to grow in the same area. You might find plants like coastal tea-tree (Leptospermum laevigatum) and manuka (Leptospermum scoparium), the two wattles ‘prickly mimosa’(Acacia verticillata), common heath, (Epacris impressa) kunzea (Kunzea ambigua), native daphne (Pultenaea daphnoides), tree broom heath (Monotoca elliptica) and parrot food (Goodenia ovata) growing with the eucalypts.

Epacris impressa
Epacris impressa
Tussock Grassland

Covers 20 % of the island and tends to grow on the richer limestone soils; it also can withstand greater fire frequency. Poa poiformis grows more commonly on areas more distant from the lighthouse and out of range of domestic animal grazing. The community mostly adjoins Allocasuarina verticillata and there appears to be active invasion of the grassland in some places.
Stipa stipoides occupies about 6 % of the island and is confined to a narrow strip around the more exposed areas of the coast, forming a zone exposed to salt spray. Soil type and fire frequency do not appear to be controlling factors in the distribution of this grass. You will find the most extensive areas of this plant on the slopes above Little Squally Cove where there is a high exposure to wild weather.

Beaches and dunes (occupy less than 1 % of the island)

Spinifex sericeus holds the sand in place, move further inland and you will find sagg (Lomandra longifolia), saltbush (Rhagodia candolleana) and (Atriplex cinerea) mingling with American Sea Rocket (Cakile edentula), ‘singing grass’ (Lepidosperma gladiatum) and Correa backhouseana.

View of Winter Cove
Winter Cove, Deal island

Clifftop vegetation
Allocasuarina verticillata on clifftop
A high proportion of the coast is cliffed or at least comprises very steep granite slopes. The species occurring on the cliffs and slopes is often very similar to granite areas with skeletal soils, further inland, except in the more exposed sites where a typical coastal flora becomes dominant. Here the mixed vegetation is usually stunted by the ferocious winds and salt spray. Some rocky outcrops on the southern coastline we call our ‘bonsai garden’ for that very reason.
Bonsai garden
In spring time (Sep-Nov in the southern hemisphere), many plants that go unnoticed during the year, delight the botanist: Clematis microphylla winds its tendrils over fallen trees as does the Blue Love Creeper (Comesperma volubile). Hidden amongst leaf litter and rocks delicate orchids reach out to the sun. 21 species have been identified – amongst them the rare  Orange-tip Caladenia (Caladenia aurantiaca), Maroonhoods (Pterostylis pedunculata), various Greenhoods, Bearded – and Helmet orchids as well as several species of Sun orchids.
The western coastal hills above East Cove are yellow with the Coast Twinleaf (Zygophyllum billardierei) and Senecio pinnatifolius, the grasslands graced by the blue stars of Wahlenbergia stricta.

Comesperma volubile
Comesperma volubile
Senecio pinnatifolius
Senecio pinnatifolius

This article was compiled with some written sources provided by Penny Tyson and Stephen Harris/ Georgina Davis.
(Trauti Reynolds.)