Wednesday, May 20, 2015

Native Caper Tree

Capparis arborea

Isn’t this a silly little plant?
It began by growing straight upwards. Then it noticed the seedlings next to it, on the shelf, and turned to grow horizontally towards them.
The reason is that these little caper trees like to borrow a trick from the climbers. When they are young, they use their thorns to scramble up through the surrounding vegetation to gain a bit of height before they start making serious tree-trunk.
Unfortunately for the high hopes of this little fellow, his seedling neighbours are not as tall as he would be himself, if he only stood up straight!
Notice the thorns on the plant aabove (Click on the photo for a closerr look). Not many kinds of plants have two thorns coming from the point where the leaf joins the stem, so this is a feature which can help you identify a prickly plant. Locally, the only plants like this are Capparis, Apophyllum,Carissa and Strychnos species.
(In my original version of this post I omitted Strychnos from this list. I forgot it because it is so very uncommon around Toowoomba. A reader put me straight. Thanks Mick. I would much rather be told about it when I write something inaccurate, as I would really like my blog to be the best guide to local plants that I can produce, with a little help from my friends.)

As it grows, this little caper tree will stop making straight thorns, and start growing little curved ones like kitten claws.

Meanwhile it will replace those cute baby-leaves with larger, adult ones.

In young plants the thorns are left on the stems after the leaves fall, their neat pairs revealing that the stem belongs to a caper tree.
In older plants, the tendency to make thorns is lost, which makes them nicer to live with, of course, but leaves us without a useful identifying feature if we find them in the bush and wonder what they are. The thorns were there to protect them from munching herbivores - originally Diprotodons and the like - as they grew. Older plants don’t need this protective feature.

On growing up, my little plant can be expected to produce masses of fragile white flowers. Their buds begin to open at about 8 o’clock in the evening, releasing their sweet fragrance and attracting pollinating moths. Soon after noon the next day, the petals will fall.

Notice the long, curved white style in the centre of the flower, with a little green sphere on the end. This sphere is the plant’s ovary, and will turn into the fruit.

Here are fallen flowers, with only the scar left to mark the place where the petals were attached.

The little ovary will grow into fruits like this. They are edible when soft and ripe.

Meanwhile, the plant would have produced generations of butterflies, as it is the favourite food plant for a number of different species...

...including this one, the Caper White Butterfly, Belenois java. Usually the caterpillars go unnoticed on the tree, but sometimes, when conditions are just right, they strip the trees bare and clouds of these lovely insects migrate for as much as a thousand kilometres in their search for new host plants for the next generation of babies.

We have several local species of native caper, and one other close relative. To find my blogs about them,  use the white search box at top left to find references to the family CAPPARACEAE

Wednesday, May 13, 2015

Dangerous Fruits

Giant Stinging Tree, Dendrocnide excelsa
This wonderful tree pulls more than its own weight as a member of a rainforest community.

It is a fast-growing pioneer tree, quickly filling spaces in rainforests caused by falling trees or human interference.
It grows to be one of the most magnificent tall trees in the forest, becoming part of its upper canopy.

The leaves of young trees tend to be held horizontally, and are a particularly pretty part of the rainforest scene.

Their translucent light green colour makes the overhead leaves stand out against the darker leaves of the higher canopy.

At the end of the tree’s life-span its soft timber breaks down rapidly, completing the cycle of growth, death and decay that provides habitat for so many species.

This tree had fell across a path at the Bunya Mountains, and has been cut by the National Park rangers to reveal the wonderful fluting of the trunk. Note the tiny stinging tree seedling in its folds. Like seedlings of many other species around it, it is entering the race to fill the canopy gap left by the old, dead tree. What are its chances?

The luscious fruits of stinging trees are eaten by birds and bats. In theory, people can also eat them, but, as they are likely to have stinging hairs amongst the fruits, the outcome could be deadly and is definitely not worth the risk!

The leaves support leaf-eating insects, which sometimes make lacy skeletons of them. Insects are part of the food chain, becoming food for birds, and other animals. The skeletonised leaves are yet another bit of evidence that the stinging tree is playing its part in a healthy local ecology.

How Bad is the Sting?

Because it loves to fill spaces, giant stinging tree often pops up beside National park trails or roads, and visitors learn to be wary of its giant leaves. I find their sting about equal to that of the ordinary nettle Urtica incisa and not very dangerous. However,  different people react differently, so it is best always to be wary of any nettle, whatever the plant’s size.
It would be possible to confuse this plant with a much more dangerous plant, the Gympie stinger, Dendrocnide moroides. Gympie stinger is not native to our district, but grows a little to the north of it. It  is a shrub or small tree with leaves very like those of the giant stinging tree, and its sting is very strong.
Science (and my own experience) tells us that the old wives’ tale of rubbing a nettle sting of any kind with cunjevoi sap to reduce the sting is completely useless. Hair-removal wax strips are the recommended first aid. Some people claim they get at least a partial cure by applying the sticky section of band-aids or elastoplast, the stickier the better, and ripping it off to pull out the little stinging hairs.

A Valuable Plant.
Aborigines made nets and lines from the fibres of the bark of the roots, but modern people have found no used for the soft timber, and of course none of us like to get stung! As a result giant stinging trees have been somewhat underappreciated.
So I am delighted when I find it for sale in certain specialised nurseries. It sells to people for revegetation projects where its potential to make a very high contribution to their local ecology is appreciated.

For notes on the other members of the Urticaceae family, use the white search box at top left

Thursday, May 7, 2015

A Very Variable Boonaree
Hairy Boonaree
Alectryon pubescens
I found another leaf shape, at the Bunya Mountains last weekend, to add to my collection of different leaf shapes for this highly variable plant.


It tends to grow in the same places as the related scrub boonaree, Alectryon diversifolius, and can be mistaken for it. Both are large shrubs or small trees. However, hairy boonaree is distinguished by its larger leaves, and despite the scrub boonaree’s scientific name, P. pubescens is the one which has by far the greatest diversity of leaf size and shape. Its leaves are generally larger than those of A. diversifolius , and most plants have at least some leaves with a lobe or two close to the base of the leaf, a thing which A. diversifolius never has.

Hairy boonaree gets its name from the hairiness of various plant parts, most notably the seed capsules. They always begin as double fruits, but quite often only one of the two develops a seed.

By contrast, the Scrub Boonaree

Alectryon diversifolius
has a rather limited range of leaf shapes...


 ...and its capsules are not hairy.


Wednesday, May 6, 2015

The Streblus Mystery

Whalebone tree, Streblus pendulinus (Streblus brunonianus)

Why do some of our local Streblus seedlings have mature-shaped leaves from birth, while others have odd elongated leaves with lobes?
This seedling at the Bunya Mountains shows the whole range, from long thin baby leaves to the adult-shape leaves at the top.

Here is a closer look at the leaves. I didn't put them in order of age. Leaves like the narrow one at the bottom of the photo were produced first. The leaf second from the top is the mature leaf shape.

So far as I can discover, the reason for the difference is not known. I have wondered whether it indicates whether the seedling is a male or female tree, but have never found anyone who has tracked a seedling’s life from juvenile leaves to flowers to find out.

The male flowers (above) are very obviously different from the tiny green female flowers.

Female trees have these little yellow fruits, which are attractive to birds, including chooks.

In the Streblus fruiting season, these chooks run to my friends’ female whalebone tree, as soon as they are let out of their yard each day. They scratch in the litter for newly-fallen fruit, and will jump up to get them off the tree.

Like so many trees of our drier rainforests, whalebones can be tall trees with no low branches, when they grow in forests. They can also thrive in dry, hard country, changing their shape to suit their conditions.

The paddock this tree grows in has probably been supporting cattle for at least a century. The tree hadn’t even managed to form its typical single trunk before the cows started “pruning” it, but it has struggled on to produce this wonderful bird-sheltering plant, with tight growth of branches and leaves.

For more on whalebone trees, see my blog of February 16, 2008,
or type Streblus into the white search box at top left.

Monday, April 27, 2015

Roots Matter

The healthiest small trees are the ones that have “volunteered”, growing in soil of their own choice and having the freedom to develop their roots according to their own species growth rate and style.

Here is a local native plant of typical dry rainforest/vine scrub type (Cupaniopsis parvifolia). It was planted by a passing bird on a pile of rather loose mulch, from which I was could dig it out to show the complete root system down to the tiny hair roots. Note the seed, on which the seedling is still feeding, at what was the surface level of the mulch. Now notice that that the roots are already almost four times as long as the stem.

When we try to create healthy tree seedlings in pots, we need to consider how they prefer to grow. The prettiest potted tree in a nursery is not necessarily one that will make a good garden  plant. This particularly applies to native trees and shrubs indigenous to Australia’s inland. In most cases, the secret of these plants' drought hardiness lies in their "instinct" to get their roots deep down into the subsoil as fast as possible.
Misunderstanding of this, and poor management in the seedling in its earliest months of life,  are some of the reasons Australian plants have a reputation of being short-lived in the garden. Good nursery practice for this kind of plant focusses on creating roots which are pointing directly downwards, with their growing tips ready to plunge deep as soon as they are put into the soil.
At the Crows Nest Community Nursery, where plants are grown and sold in tubes, we do our best to discourage those cautious customers who say "I'm going to look after this little plant really well! I'll  pot it on and leave it in a bigger pot for six months before I plant it out ".
"No", we say, "please don't"!

Let me explain.
A really good local native tree or shrub, for this district (and any other district where rainfall is erratic) is one that has been grown in a tube that is as close to bottomless as it can be, without the potting mix actually falling out.

Contrast the bottom of this 2 inch (5cm) tube with the pot beside it.


Now notice the vertical lines, showing that inside the tube there are ribs designed to ensure that any root-tip that hits the side of the pot and shows a tendency to turn sideways, will be redirected downwards.
In a good native nursery seedlings in such tubes are then placed on a freely draining wire bench, and watered from above.

The result is that roots gallop to the bottom of the pot, where they are air-pruned, as shown here.

Notice that even this little native plant has already sent its roots to the bottom. Let’s have a closer look at it.

Who would guess, if they saw it in a “big" pot that its roots would already have suffered from being confined? They would have turned a corner as they hit the bottom of the pot, and the little plant would already be on the way to being pot-bound.

Now compare the tube with the pot from the side. At first glance, the big pot seems to be offering really generous root-room, doesn’t it? But what kind of root-room is it?

One thing we definitely don’t want our local plant species to do is to waste their time producing lots of root in the top five or six inches of soil.
When we do this to our native plants, we are being misled by the gardening traditions we brought from Britain and Europe. They were developed in places where rarely a week goes by without any rain, and roots near the surface were an actual advantage. Here in Australia we need to help our newly planted garden plants to survive the real Aussie fact of frequent drying-out of the top layer of soil.  Why not work with the plants' natural deep diving tendencies, rather than against them? By putting them in pots, we force them to go against their own nature, wasting their time developing good root systems for growing in pots, in nursery conditions. Despite their native drought hardiness, they will be handicapped as soon as they are planted out, by their unnatural tangle of close-to-the-surface roots with their tips pointing every which way. They will be more vulnerable to dying from soil moisture loss than a much smaller tube-grown plant would be.

What we want for planting out is something like this healthy specimen, Notice that its root tips have been trained to the bottom, ready to dive into the safer soil deep down as soon as it is planted. (Click on the photo for a closer look at them). Ideally the planting hole would be twice the depth of the tube, and not very wide. It would be filled with water once or twice, and the water allowed to soak away. Then a reservoir of water, consisting of a cup or two of well-soaked water crystals mixed with the soil in the bottom of the hole, would be positioned to sit below the newly planted tree.
With that kind of start in life, the plant will quickly develop the roots it wants, which grow rapidly to be much longer than the above-ground part of the plant. Once this is achieved, the top of the plant will start to grow as well.

Is it Pot-bound?
Some customers express concern that a plant like the above is “pot-bound” because they see that the soil is full of roots. It is not.
The crucial part of the expression “pot-bound” is “bound”. The root tips in this plant are not suffering from confinement at all. The little tube could actually afford to be very much more full of roots, without any hint of "binding".
Consider the tube-versus-pot photo above, however. Transfer a plant from the tube to the pot and pot-binding would start to happen as soon as the roots made that extra centimetre of growth and hit the bottom. Looser soil might create the illusion that the roots are better off, and with the kind of care that people give to plants in pots, the above-ground part of the plant would put on size. Once in the soil, however, that mish-mash of roots would take time to sort itself out, if it ever did. The tube-grown plant would have much deeper roots than it's pot-grown friend in a matter of weeks. Many gardeners have put a healthy-looking pot-grown plant into their gardens, only to have it fail completely from root-binding, or to be a rather stunted  specimen with a short lifespan.
Even with tubes, it is possible to create a pot-bound plant. The way to “achieve” this undesirable result would be to interfere with the free draining and the air-pruning features that the tube is designed for. Keeping it on a solid surface, where it might spend part of the time with the lower portion of the pot damp, can do it. Bottom watering does it even better.
So the best thing to do with a small plant bought in a tube is to get it into the ground as soon as possible.

Our native plants don’t like to be brought to the stage of maximum prettiness in their pots before they are planted out. Nor do they want a lot of leafy growth. What they need are gardeners who understand that optimum root development is the first priority.

Strength, long life, and beauty will follow.

Saturday, April 25, 2015

An Interesting New Blog

You might like to have a look at this new local blog.
It is called Moths of Toowoomba.
It illustrates how growing local plants in gardens enriches the local fauna.
Moths, both adults and larvae, are a major food for birds and micro-bats, so every plant that attracts moths, besides bringing some delightful little creatures to the windows at night, enriches the total biodiversity.

This moth's host plants are Psydrax species (also known as canthiums), which are very attractive garden plants in their own right.
(Use the search box top left to find what I've written about several Psydrax species, on this blog).

Box Leafed Canthium

Psydrax odorata forma buxifolia
This small tree species had one of its magnificent flowering years, all around the district, this year.

Having delighted us with its lovely fragrant flowers, as well as delighted the insects (and the birds which feasted on them), it is now ripening fruit. There will be a second feast for the birds, shortly.
This is a plant that is rather slow-growing, but very pretty from infancy, with its geometrically neat, paired branches.
Here is a pretty specimen in Peacehaven Botanic Park at Highfields.

Its small rounded shiny leaves have a (very) vague resemblance to the English box which is the reason for it’s common name. (Won't it be nice when English-speaking Australian culture has matured to the point where our plant names reflect a love for our native plants for their own sakes, rather than always having to compare them with something from the "old country"?)
Some people call it “native jade”, because it can fill the “jade niche” in gardens for those who would rather grow a local native plant. I find it much prettier than jade. Here it is as a pot plant on my patio.
Like so many local dry rainforest plants, it is very long lived, so makes a good pot specimen for many years.
It prefers a sunny position, and is drought and frost hardy.