Thursday, December 29, 2011

Fire Pea

Tephrosia bidwillii

We have very few local plants with bright orange flowers.

This pretty little fellow was flowering last week.

It's a herb which grows among grasses in open woodlands on our local black soils, (often on hillsides), as well as on sandstone soils.

The plant looks as though it might have potential in gardens. So far as I know, no attempt has been made to cultivate it, so little is known of its growth habit.
Has anyone out there grown it? I'd like to hear from you!

Kangaroo Apple

Solanum aviculare
These pretty plants are flowering and fruiting around the district now. They are familiar in our local national parks, where they grow on red soil, and on hillside black soil. It is seen at left in the Bunya Mountains...

...and at right in Goomburra National Park.

For several months in spring and early summer, it produces generous quantities of these attractive flowers.

Gardeners who grow potatoes, tomatoes, eggplants or chillies will be able to see, from the flowers, that this is a related plant.

Like those familiar food plants, the leaves and unripe fruits of kangaroo apple are poisonous. It is farmed in several countries of the world, to produce a drug, used in the manufacture of oral contraceptives, which is extracted from the young leaves and green fruits.

Solanum aviculare is native in New Zealand as well, and Maoris (who call it poroporo) cultivate it for the edible fruit. It should only be eaten when it is very ripe.

Aborigines traditionally burned off the outer skins, before they ate them.
This plant has potential as a garden ornamental. It is a fast-growing shrub, with large plants reaching 3m high, and is unlikely to live for much longer than five years. The leaves of young plants have large lobes on them, which disappear as the plants mature. It is useful as an ornamental filler in gardens, positioned between slower-growing, long-lived plants. It is also used as a rootstock for grafting eggplant.
New plants are easily grown from seed or cuttings
Kangaroo apple is moderately drought and frost hardy. It needs a sheltered site, and grows in full or part sun.

Thursday, December 8, 2011

Kangaroo Grass

Themeda triandra

The distinctive heads of this unmistakable plant are highly visible around the district at the moment, as they begin to go through their summer colour-change. The leaves go from light green to red-brown and the pretty flowerheads ripen to a showy russet-colour.

This was once Australia’s most widespread grass, and it is one of the easiest native grasses to identify.

Deservedly our most popular ornamental grass for landscape gardening, it is also useful in floral arrangements. One of the staples of a good wildlife garden, it is very attractive to birds, which appreciate the feast of large seeds. A nutritious plant, it is popular with kangaroos and wallabies, and with introduced livestock, which have grazed it heavily since the time of European settlement. Unfortunately it is easily killed by overgrazing, so tends to vanish from pastures.
It has been used in native lawn mixes, but just as it doesn’t tolerate heavy grazing, it can be killed by being mown too frequently or too short. It grows as a tussock, rather than spreading as do the better-known introduced lawn grasses, so you would only use it for a “lawn” in an area where this might be rather roughly defined!

"Cultivated grassland" would be a better term, and it would be a pity not to let it go to seed each summer.

In pre-European times, kangaroo grass was managed with a regime of annual (winter) burning, which refreshed the plants ready for the new season. Burning is hardly practical in a garden, but a cut-back after the seeds have dropped, by hand or a high-set lawnmower, will result in more vigorous plants as well as natural regeneration. It is better if the grass cuttings are collected and removed, as this is not a plant that likes mulch.
Collecting seeds for propagation purposes can be a little tricky, as they must be very ripe - firm and hard rather than milky, and there is only a narrow window of seed-collecting time before they fall off the plants. A successful technique is to put a seed-trap under the plant to collect fallen seed, and empty it daily until enough has been collected. The seed then needs to be stored for nine months for “after-ripening” before being planted. It needs a cold period to help it germinate, so seed which is taken indoors should spend 4 weeks in the fridge, before being planted out. It is time to plant it once the daytime temperatures are over 25°.
We think of kangaroo grass as the quintessentially Australian grass, so it’s a bit of a surprise to discover that it is also native to South Africa. There they call it rooigrass - an Afrikaans word meaning “redgrass”. It is the only African species of Themeda, and it was given its botanical name there. "Themed” is an Arabic word referring to a depression where water lies after rain and dries up in summer - a clue as to how the grass likes to grow - plenty of water to get started, after which it will happily tolerate drought. It’s also frost hardy.

Thursday, December 1, 2011

Native Caper Tree

Capparis arborea

Franke Scrub at Highfields is a mass of butterflies at present, and this tree is one of the reasons. It’s a native caper, one of our five local Capparis species, and is host to at least four species of local butterfly.

This rather conspicuous plant is on the edge of the scrub. To find it, just drive around the edge and look for the butterfly-like white flowers and the butterflies that are hovering around it.

It’s worth looking for it in the morning, when the perfume of the fragile flowers is at its best. They only last a day, losing their petals by early afternoon.

This magnificent little tree may be several hundred years old, and is a good example of the naturally small dry rainforest trees which are so suitable for suburban gardens. Alas, they are sometimes undervalued - people who will see a large tree as old and therefore worth preserving may clear small ones because they don't appreciate that they, too are living relics of the pre-European era, so have heritage as well as environmental value.
This specimen's age is the reason that it is difficult to find the spines which are the most obvious identifying characteristic of caper species. They grow in pairs at the base of each new leaf, on all but the oldest trees. In seedlings, the spines are long and straight, but as the trees mature, they produce short, curved ones. Young trees might still have the remnant paired spines on their trunks, but older trees lose the prickly habit. Spines like this evolved as part of the "arms race" with herbivores. They protect the plants, which are otherwise very tasty, from being eaten, when it is young. Taller plants with sturdy trunks are not so vulnerable, so don't need the spines.
For more about this and other local Caper species, see articles posted November 2009, and December 2008.

Mapoon Bush

Psychotria loniceroides

This plant is flowering beside the walking track at Ravensbourne. The starry white flowers will be followed by yellow fruits which are edible when very ripe, but are rather insipid in flavour. The birds like them, though.

The name “loniceroides” suggests that the soft, velvety leaves are like Lonica - honeysuckle - but you’d have to say that the resemblance is slight!

In nature it grows as an understorey plant in dry rainforests. In a garden, it grows as a shrub, usually about 2m high. It is suitable for growing under trees and in densely shady places where it may stretch to reach the light, reaching as much as 5m in height. For a compact shrub in those conditions it would need pruning to keep the shape neat and the foliage dense. In full sun it won’t grow so high, but the foliage will be denser, and it will flower and fruit more prolifically.
Mulch to keep the soil damp will also improve the appearance of this drought-hardy plant. It needs well-drained soil, and grows very well on our local red soil.