Friday, November 30, 2012

Black Bean

Castanospermum australe

It takes a few years to see a reward, when we plant rainforest trees, but black beans are among the ones which put on a good show while still quite young. This lovely specimen in Highfields has been flowering for several years now. I don’t know it’s age, but it’s probably about 10 years old. The species is great value for a larger garden. It will grow quite fast to make a medium to large tree - about the size of the familiar camphor laurels, which are used as street trees in Toowoomba. It's dense, dark green canopy makes it a very good shade tree.

 The flowers appear on old wood, inside the canopy.

Flowers at all stages of development are on the tree at the same time, and make a perfect illustration, if you happen to be wanting to teach children how flowers “turn into” seeds.

These little green pods will develop into large brown seedpods, whose huge seeds will germinate if left sitting on damp soil in a pot - another interesting thing for children to see. They can use the pods as boats, once the seeds have been taken out. The circular depressions left by the seeds make good “seats” for tiny toys.
The special shape of the flowers shows us that the plant wants to attract nectar-eating birds as pollinators. The jacaranda in the background (an introduced tree, native to Amazon rainforests) has very little appeal to wildlife. The black bean, however, is pulling its weight as an active contributor to a healthy suburban environment.
It is drought hardy in the Toowoomba area, and tolerates light frosts.
For more on this plant, see Nov 2009 (or use the “search” box, at top left).

Black-fruited Sedge

Cyperus tetraphyllus
Plants’ scientific names can be as unsatisfactory as their common names. “Tetraphyllus” means “four leaves”, but this is obviously not a four-leafed plant.

I wonder whether the name might have been a reference to the leaf-like bracts that surround each seed-head. Perhaps the first plant examined seemed to be consistent in having four of them?

In practice, though, they can have anywhere between three and six bracts. In this plant, which I grew from seed at home, they consistently have five, of varying sizes.

Isn’t it a lovely, spiky-looking thing? The spikes are soft, though, and don’t prickle the legs of passers-by.
In the wild, this plant is found lining the edges of shady rainforest paths. When not in seed, it resembles the introduced plant, mondo grass, and would make an excellent native substitute for it. The lovely seedheads are a bonus.
It is easily grown from seed (as are all our native sedges), but can also be purchased from specialist suppliers.
It is somewhat drought tolerant (growing naturally in Goomburra National Park), but probably won't tolerate frost.

Thursday, November 15, 2012

Split Jack

Capparis lasiantha
   We rarely see these plants on the eastern side of the Condamine. I found this one in Edgefield Road North-east of Dalby, where the basalt soil is blending into sandy alluvial soil.
   Like our other local native capers, it has flowers which resemble butterflies, with its four petals arranged in pairs.
Also like other native capers, the plant is well-defended by ants. (I can find no information about this well-known association between ants and Australian Capparis species. I imagine that they are being attracted by nectar-secreting glands (nectaries)  that have evolved for the purpose. Can any of my readers enlighten me?)
   The flowers of most of our native capers are short-lived, losing their petals by mid-afternoon. Their decorative qualities come from the sheer quantifies of flowers produced. However these little ones were still hanging on, quite late in the day. They seem to open white and turn yellow, but I don’t know whether they last for more days than one.

   Split Jack is a scrambling climber, hanging onto its host plants by the sharp little pairs of spines at the base of each leaf. Some capers lose their thorniness as the plants age, but this one seems to be a thorny little devil all its life. (Now there’s the thing to grow on a fence, if you’re worried about prowlers!)
   They can climb to about ten metres, but are more often seen on fences where they can grow quite bushy, or scrambling over themselves to make dense, bird-sheltering shrubs. They grow densely without pruning, but are happy to be confined to a desired shape and size with the secateurs.

Like all Capparis, they are hosts for a number of butterfly species, like this Caper White (Belenois java).

Grow a split jack, (or a native caper of any kind) and you will always have native butterflies in your garden!

Short-Jointed Mistletoe

Korthalsella taenioides
(Korthalsella breviarticulata)

A roadside stop to look at some flowering Capparis lasiantha last week,  in Edgefield Road near Dalby, was particularly rewarding.  I also found this perfect little mistletoe, growing on the caper plant.

Isn’t it a darling little thing?
The whole plant is about the size of an orange - which is as large as it gets - and it is fruiting very prosperously, as you see.
Apparently these seed capsules are weakly explosive, likely to burst, spraying out their sticky seeds, when touched. It’s thought that the plant spreads on the birds’ feet and feathers.

Korthalsella species are the only known host plants for the Yellow-spotted Jezebel butterfly, so the survival of this little plant is important to them.

It is known to grow on a wide range of dry rainforest species, including Alectryon diversifolium, Geijera parvifolia, Melodorum leichhardtii, and various Capparis species, and can probably be transferred to these plants by hand. Paople who want to attract these butterflies to their gardens might like to attempt it, in summer when seeds are ripening.
(Like all seeds, mistletoe seeds and seedlings like to be watered until they are established.)

Thursday, November 1, 2012

Scrub Whitewood

Atalaya salicifolia

I found this delightful little whitewood tree beside the New England Highway, north of Crows Nest, last weekend. It is flowering its little heart out.

 Left to reach its potential, it will grow to be a shady small tree with a trunk 30cm in diameter. Typically of many plants of our dry rainforests and vine thickets, it is suitable for growing in small gardens, or as a street tree.

By summer, its flowers will develop into bunches of brown, winged seeds.

Whitewoods are decorative from an early age, because of their interesting juvenile foliage.  
The leaf shown below is from a young plant 1 metre high. Note the winged rachis .

This more mature leaf came from the young roadside tree shown above. It has intermediate foliage - leaves broadening out, and the rachis-wing narrowing.

In older plants, the rachis disappears altogether, but the prominent swellings (pulvinules) at the base of the leaflets remain, helping us to identify the tree.

It is drought hardy, but tolerates only the lightest frosts when it is young.