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Native Plants

epicormic growth after fire boronia pinnata in mid-winter

 

This paragraph is an introduction to a section on plants, flowering plants, most of which may be found in the local area. Flowering plants (or angiosperms) did not always exist on our planet. They are believed to have evolved from gymnosperms over 200 million years ago. However, evidence for their existence only goes back to about 140 million years ago (i.e. early Cretaceous). Gymnosperms (naked seeds) are plants such as conifers and cycads whose seeds are unenclosed. The nakedness refers to the actual seed and has nothing to do with the fact that they may initially be contained in a cone. The most important and obvious distinguishing characteristic of angiosperms are their flowers and fruits which contain the seeds. The evolution and diversification of flowers allows angiosperms to adapt to many conditions and hence are found in most parts of the world (although not Antarctica). As part of this evolution many methods of pollination exist, and many different pollinators.

Some of the plants here are local and some come from further afield but have been introduced into the reserves and our own gardens. A section on seagrasses is included but as will be seen this is for completely different reasons. Above the left-hand picture of a gum tree coming back to life reminds us of the problems associated with bushfires and the amazing ability of the Australian bush to recover. The right-hand picture shows a local boronia in flower at the beginning of July - the middle of winter. Although most plants start flowering in Spring there can be colour at all times of the year.

Local Native Plants

Boronia pinnata

Boronias are a well known genus containing several species. Boronia pinnata (right hand image above) is a common species found in the sandstone areas of eastern NSW, usually in dry sclerophyll woodland. Certainly it is to be found in the forests around St Georges Basin and makes a beautiful addition to any garden, native, exotic or mixed. The flowers when seen open consist of four pointed petals usually light pink in colour, which last from winter to late spring or early summer. The leaves are usually light green, about 25 mm long and opposite each other, and are formed from several pairs of opposite leaflets. Unlike some members of the genus this plant is relatively robust and long lasting in a suitable sheltered location. A small amount of pruning is beneficial. In the wild it can grow to 1.5 m, but in the garden with light pruning it can readily be kept to below 1 m and the growth thickened. To acquire Boronia pinnata you will certainly have to go to a nursery specialising in native plants. If not available then the nursery can possibly get them in for you or advise you where to go.

Boronias belong to the family Rutaceae; the name Boronia is derived from F. Borone, an Italian botanist; pinnata means feathered, alluding to the paired leaflets.

For more in-depth information on the scientific description of this and other species follow this link to a page on scientific classification.

Patersonia glabrata

Patersonia glabrata is just one species out of about twenty Patersonia found Australia wide. It is quite common locally although there are also another three Patersonia species to complicate identification. The genus is reminiscent of the exotic iris and Patersonia are commonly known as Native Iris or Purple-flag. The common name for the glabrata is Leafy Purple-flag. The plant has green to dark-green linear leaves up to about 30 cm long which emerge from the base of a single above-ground stem. This latter feature can be used to identify the glabrata. The flowers which are a striking blue to purple in colour consist of three fragile, equally-spaced petals coming from a papery bract or spathe at the end of a stalk. Individual flowers last only for the daylight hours of one day but many flowers will be produced from each bract. Patersonia glabrata can tolerate full sun and will look effective in a garden planted either singly or in number. Native plant nurseries will supply this or other Patersonia species.

Patersonia belong to the Iridaceae family; the name is derived from Colonel W. Paterson, a Scottish plant collector; glabrata means hairless (leaves).

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Tetratheca thymifolia

Tetratheca thymifolia, or Black-eyed Susan as it is commonly called, is a beautiful addition to a garden and is a species usually available in nurseries, especially native plant nurseries. Large-flowering and white variants are sometimes available. It quite common in the forests and woodlands around St Georges Basin and is most noticeable in late winter and spring when it is in flower. Thymifolia is a small shrub up to about half a metre in height consisting of many erect branches with small elliptic leaves arranged in rings of three, four, or five. The four-petalled flowers are pink to mauve, have a dark inner centre (which gives them their common name), and hang down like small bells on long stalks.

Tetratheca belongs to the family Tremandraceae; the name tetratheca means having four cases (pollen sacs); thymifolia means thyme-like leaves.

Seagrasses

Why are seagrasses included in this section on native plants? Well because that is precisely what they are - native plants. They are flowering plants which have evolved to live in a marine environment. So they are not the kind of plant which you can grow in your garden but are very interesting and important nevertheless, and are common in the Basin. So for these two reasons they have been included here.

Seagrasses have been around for a long time - it is thought that they first evolved in the early to middle Cretaceous, probably somewhere between 144 and 100 million years ago. Like terrestrial grasses they undergo photosynthesis, have flowers, leaves and roots, and reproduce via seed. While their flowers are small their pollen grains are unusually large. Unlike terrestrial plants pollination does not depend on insects or other creatures. Seagrasses also spread by sending out rhizomes from which secondary plants grow. They are to be found in shallow, sheltered waters like those which are to be found in St Georges Basin and parts of Jervis Bay. They grow and anchor themselves in soft sediments, such as sand or mud.

Australia has a very large area of seagrasses - probably the greatest in the world. Because of this our seagrasses are an important sink for carbon dioxide and should be protected for this reason. However, the effect of possible changes induced by global warming - such as salinity, light levels, and temperature - are not well known or understood.

The benefits of seagrasses are considerable. They provide a nursery habitat for small fish and crustaceans, and their leaf detritus is consumed by crabs, prawns and fish. In tropical waters seagrasses are vital for dugongs and turtles. Their leaves are continuously being shed and can produce banks of debris along the shore, thus producing nutrients which improve the productivity of the ecosystem. Their roots stabilise the sand and mud, and hence the shore line; while the leaves reduce turbidity. Unfortunately seagrasses are effected by disturbance and their extent has declined since European settlement. Severe weather events, such as Cyclone Yasi which occurred recently, can have disasterous effects on seagrass beds. Recovery can take a considerable time. It is considered that Posidonia (see next paragraph) beds may take centuries to recover from significant damage such as dredging!

The four most common seagrasses found in NSW waters, including the Basin, are (1) Posidonia australis (strapweed), (2) Zostera capricorni (eelgrass), (3) Ruppia megacarpa (sea tassel), and (4) Halophila ovalis (paddleweed). Because seagrasses undergo photosynthesis the water depth in which they will grow depends on the water clarity. In St Georges Basin Posidonia, Zostera and Ruppia grow in depths up to 3.5 m while for Halophila the maximum depth is 5m. The seagrasses grow in the shallows all around Basin and in total cover about 8 km2 in area.

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Isopogon

This endemic genus belongs in the same family (proteaceae) as well-known Australian natives banksias, grevilleas and hakeas.

There are two local isopogons or 'drumsticks' as they are commonly called because of the appearance of the spherical woody cones which remain after flowering. The two species are anemonifolius and anethifolius. These are very similar in appearance differing mainly in their foliage. With their bright yellow flowers in spring, and drumstick cones throughout the year, the local isopogons make distinctive and attractive additions to a native plant garden. Both species are long lived, and resistant to leaf blemishes, drought, light frost, and attack by insects. Some older plants have a lignotuber which aids regrowth after bushfires.

Isopogon anemonifolius (broad leafed drumstick): The flat leaves are three-fingered with each finger being further divided, and dull green in colour sometimes with a touch of light purple. The multi-stemmed plant grows to about a metre in height, perhaps a metre and a half. It can be purchased in some nurseries specialising in native plants. A dwarf form may also be available for sale.

Isopogon anethifolius (narrow leafed drumstick): The leaves are shiny green and multi-fingered where the fingers are needle-like. The stems often have a reddish tinge. The complete leaf tends to occupy 3 dimensions whereas the anemonifolius leaf is flat and 2-dimensional. This isopogon, also multi-stemmed, grows to between 2 and 3 metres in height.

The name isopogon is derived from Greek and means equal bearded which refers to the hairy covering on the cones after flowering. Anemonifolius means having leaves like those of (some) anemonies. The name anethifolius tells us that the leaves are like those of a northern hemisphere genus called anethum.

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Orchids

greenhood orchid

Orchids are a very common plant family found all over the world in temperate, tropical, and equatorial regions. Indeed the orchid family contains the most flowering species on the planet. Australia has its own members of this family and some of these are to be found in the Bay and Basin area. There are more than 13,000 orchids in Australia and there are close to 150 known in the Shoalhaven area. The best known east coast orchid is probably the common Sydney rock orchid which is often found on the rocks and cliffs of the escarpment. It can be purchased in some nurseries and can readily be grown in our back gardens. Many of our orchids are small and not very obvious to the casual observer unless they are in flower. The flowers can be very unusual and spectacular, even bizarre, for people familiar with more common native plants. Orchids flower throughout the year depending on the species. The photo shown here shows the flower of a local orchid, Taurantha concinna, whose common name is the Trim Greenhood. There are other "Greenhoods" and it is difficult for the amateur to distinguish between them.

Local orchids are to be found in a variety of ecosystems - heaths, swamps, rainforests, wet and dry sclerophyll forests, and vegetated coastal dunes. In terms of altitude they range from sea level to the plateau above the escarpment which can be above 500 metres, even to 700 metres on Pigeon House. Some orchids are terrestrial i.e. growing in the ground, while some are lithophytes and grow on rocks and cliffs; others are epiphytes and grow on trees. In temperate regions most orchids are terrestrial, in tropical and equatorial regions most are epiphytes. Native insects play an essential role as pollinators in the life of most (but not all) orchids. The structure of some orchids mimics that of a particular female insect thus attracting a male pollinator.

Note that orchids are protected and cannot be collected without special permission. Some orchids in fact are Endangered or Vulnerable. Very recently a book on local orchids has been published (see below for details) and the interested reader is referred to this for more information.

Bibliography

Stephenson, Alan W. Orchid Species of the Shoalhaven A.W. Stephenson 2011 {ISBN 978-0-9581679-1-9}

Acknowledgement

Some advice from Alan Stephenson is gratefully acknowledged.

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A Puzzle

isopogon

Here is a puzzle for those who like a challenge. The image opposite shows the flower head of an isopogon anethifolius (it could equally well be anemonifolius) before most of the individual florets open. An estimate of the Golden Ratio can be obtained from this image. Can you determine this estimate? If you don't know what is meant by the Golden Ratio finding out will be the first step towards the solution!

If you wish you can transmit your answer via the email address on the home page. Unfortunately no prizes other than satisfaction.



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