17 February 2008

Eucalyptus propinqua

Otherwise known as grey gum. There are so many trees given this name on the east coast of Australia, because there are rather a lot of grey gums. About ½ dozen are members of the Grey Gum Group - rather obviously named for their grey bark. All members of the group are prized for the strength and durability of their timber, and in the early days of European settlement were heavily logged for use in construction.

The tree can appear to be a small mallee in tougher sites where the soil doesn’t quite suit, but on the Central Coast we generally see a beautiful tall, elegant tree, 35 m or so high, with a tall, straight cylindrical trunk.

The bark sheds to the ground, there is no collar.

Some people complain about the mess that gum trees leave in their gardens. It is true that they shed huge quantities of bark, but only once a year, and it makes wonderful kindling, is a good weed suppressant, and most importantly, makes a home for uncountable creatures as it breaks down and becomes soil. They can grow to be very large tree so are not really suited for today’s smaller gardens in any case. Whilst we hang on to our remnant bushland you can enjoy them that way, interspersed with other beautiful gums.

The name, grey gum, is a dead give away in what to look out for in the tree, but at this time of the year they can surprise.

Most of the time they are a rather uniform, granular surfaced, mottled grey, but once a year the bark is shed in huge slabs and displays new colours, ranging from pale cream to light orange.

Then, more occasionally, when the rainfall has been heavy over spring and summer, the same process is carried out - but this time displaying a most vivid orange trunk.

This year, 2008, the grey gums are spectacular. Tall streaks of bright orange can be seen glowing through the rich greens of the bush. It really is a spectacular sight for a month or two.

The last time I saw them this good was in 2001, also following a few months with a lot of rain. In the afternoon light after a wet day they are just fabulous. I want to use words, like stupendous, gorgeous, fantastic, mind boggling, etc. It’s the only way to try and get across just how wonderful these trees are.

Once the new bark weathers the colour fades to a light grey then weathers a little more until the medium grey is back for the rest of the year. The magic comes to an end.

Like most of the eucalypts on the East coast they have broad lanceloate leaves, 14cm x about 3.5cms. The leaves are discolorous, glossy, green above and lighter below.

The many chewed holes in the leaves attest to the fact that they are enjoyed by wild life.

The bark is often covered in scratches too which I suspect are made by goannas as they patrol the trees looking for food, birds nests for example.

The trees are also a food source for koalas so I suppose there is a chance the scratches are their doing. I have never seen a koala in the wild in my neighbourhood, but I have heard them calling during mating season so that remains a possibility.

Lastly the flowers. Like all east coast gums they are white. In the case of this particular grey gum they are also sparse and held generally high in the canopy and so the searcher doesn’t often see them with the naked eye. It is surprising how easy it is for small white flowers to blend in with canopy and the sky as you search both.

The buds are held in groups of 7 to 15 and are pointy. There is a scar across where the bud top will fall away to expose the flower. They flower January to March.

The following fruit hang on the tree for quite a while. They are small, round and with a cross in the top, rather like a small round hot cross bun

3 February 2008

Gomphocarpus fruticosus

Gomphocarpus fruticosus has many common names; Narrow-leafed Cotton Plant, Cotton Plant, Balloon cotton bush, Swan Plant, Tinder Plant, Tennis Ball bush and Milk Weed.

Though the plant is South African in origin it has become naturalised in the warm temperate zones of Australia. It is a weed of grasslands and disturbed sites in partial shade or full sun and may be spotted growing along road verges and railway lines. This photograph was taken alongside a busy road where the patch of plants was roughly 4 metres by 1 metre, hardly plague proportions.

It is a short-lived perennial shrub growing half a metre to 2 metres high. The leaves are mid green, 10 cm long and narrow, and arranged in opposite pairs along the stem. Like other members of the Asclepiadaceae the plant exudes a milky sap if the stem is broken or cut, which contains cardiac glycosides.

When working amongst these plants protective clothing is suggested, as some people have an allergic reaction to the sap. In South Africa the plant has a history of use in traditional African medicine. The dried leaves and roots were used to alleviate headaches and the Afrikaans settlers used the dried seeds as tinder.

The 15mm, tiny, creamy-white flowers with purple coronas fall in clusters from the leaf axils near the end of the stems. The bush continues producing flowers throughout spring and early summer and, though small, the sheer numbers of the flowers make them very attractive indeed.

These develop into large inflated bladder- like balls, which become straw coloured with age and then later split to disperse the seeds on the wind.
Compared to the size of the flowers the seed pod is enormous, being 60 mm long or thereabouts.

These oval, slightly pointed fruits are sparsely coated with soft protuberances.
I hesitate to name them spikes or prickles because that has unpleasant connotations, whereas these are rather soft and rubbery against the skin, even when dried.

The fruits are the cause of the common names swan plant and cotton bush. Using your imagination one could make a swan out of the bend of the stem and the green seed pod but the cotton bush epithet is more easily understood, because when the fruit splits to disperse the wind borne seeds they look very much like an open cotton boll. They have no relationship to cotton however.

Many find the fruits attractive in their own right and they are often used in floral arrangements or floated in bowls in place of flowers.

Gomphocarpus fruticosus makes it onto the Noxious Weeds List for Western Australia and onto the Australia wide Weeds List. This is because the plant is poisonous if eaten by domesticated animals and is an expensive nuisance if it contaminates a crop.

The leaves are not poisonous to all living creatures however. The Danaus plexippus butterfly spends the larval stage of its life munching on those very leaves which cause problems to domesticated animals.

The larvae are beautiful and fascinating in their own right. Instead of a flower arrangement a branch of Gomphocarpus fruticosus, complete with caterpillars and pupa, make a very unusual living arrangement.

Just be sure to pack the edges of your vase with something like screwed up newspaper, poked in firmly, otherwise the caterpillars may drown if they decide to go walk about. It is very exciting for adults and children alike to watch the life cycle of caterpillar to adult butterfly. Be sure to warn children that all parts of the plant are poisonous to them.

Those of us who are lucky enough to have space to set aside for a wild garden can enjoy the sheer beauty of the caterpillars, butterflies, flowers; and even those bizarre seedpods, outside.

So though Gomphocarpus fruticosus is listed as a noxious weed let’s allow it to grow along railway embankments or road verges. There it spreads in a contained manner, and is just about eaten bare by the end of summer. The adult butterflies then bring pleasure and enjoyment to many people.

Whilst neither Gomphocarpus fruticosus nor Danaus plexippus are natives to Australia if that is going to be held against them then most of us are going to have to pack up and move out with them.