Saturday, July 31, 2010

Devil’s Marbles - or Johnny Apple?

Eremophila debilis (Myoporum debile)
This little plant suffers from having too many names!
Johnny Apple is a name of long standing, but only seems to be known by older people these days. It is probably based on the tastiness of the sweet little fruits.
“Devil’s marbles” is a rather new invention, and (I think) a delightful one. It is based on the botanical name “debilis” , which really has nothing to do with any devil, but merely tells us that this is a prostrate plant.
The plants are also called “winter apples”, and are valued for the long-lasting bright pink fruits, which look their best at a time of year when a garden of local native plants might be short of colour.
In summer they have pretty little trumpet-flowers, which are pink in some areas and mauve in others. (Can you tell me what colour they are at your place?)
I photographed this plant at Irongate last weekend. Note the purplish tinge of the foliage, which I suspect to be the result of frost.
Johnny apples are very good value in gardens. They tolerate a variety of soil types, from sandstone soils to heavy black clay. Individual plants live for 10 - 20 years. They are easy to grow from seed or by layering, so replacement of old plants is a simple matter. Meanwhile, pruning increases the vigour and lifespan of the plants, and tidies them up if they are made unattractive by a heavy frost.
They can make a dense groundcover. For this purpose, plant them close (30cm apart), and prune them when they start to meet up, to thicken up their growth.
They never need watering in our climate, but of course will grow faster, especially when young, if given a bit. Like all plants, they also like to be well-watered after pruning.
In the case of severe frosts, the hardy rootstock of a vigorous plant will survive to regrow, even though the foliage may succumb. In our district, it is best to grow plants from seed sourced west of the Dividing Range, as these are likely to be more frost hardy.
New plants are easy to produce for yourself, from seed.
For more on this plant see July 4 2008

Saturday, July 24, 2010

Pumpkin Soup at Peacehaven

There are great plans afoot for

National Tree Day
at Peacehaven Botanic park, Highfields,
next Sunday 1 August, from 8.30am to 1.15pm

It is a great opportunity to see Queensland’s newest Botanic Garden for yourself, and find out about its plans for the future.

There will be:

  • Guided tours
  • 800 free trees to be given away
  • A wildlife survey (Please take 4 minutes to fill it out and have a chance to win great prizes in a lucky draw )
  • Information from these groups:
Toowoomba Landcare
Greening Australia
Friends of Franke Scrub (Highfields)
Toowoomba Field Naturalists
Wildlife carers
HOPE (Householders Options to Protect the Environment)
  • Food for sale - all profits to go to the park
Hot and cold drinks
and last but not least - Pumpkin soup.

It could all be a lot of fun. Hope to see you there!

Bright and Cheerful Twin-leaf

Roepera apiculata (Zygophyllum apiculatum)

One of the delights about living in this part of the world is that even in winter - and there’s no doubt the plant world is having a rest just now - there are always plants in flower.

At Irongate, the twin-leaf is blooming and abuzz with insects, which are no doubt grateful for the plentiful supply of pollen and nectar, in this season when flowers are in short supply.

This caper gull Cepora perimale (showing its winter colours) didn’t much like being followed by a photographer trying to get up close, but wasn’t going to let itself be chased away from the twin-leaf patch all the same.

For more on this plant of our Darling Downs blacksoil, see August 2008

Needle-leaf Mistletoe

Amyema cambagei

Here’s a plant that hides itself well!

I would have walked right past it on this tree, if my attention hadn’t been drawn by the much more conspicuous “variable mistletoe” Amyema congener. (Notice its leaves in the photo at left.)

Yet like many “edge trees” this belah Casuarina cristata at Irongate is carrying a large community of mistletoes.
Most of them are the well-camouflaged needle-leaf mistletoe, and once I had noticed it, I realised that it was flowering prettily.
It’s a curious thing that some mistletoes have evolved to mimic their most usual hosts. At first glance this seems self-defeating. Surely a plant wants to be conspicuous to the birds which eat its fruits, and therefore distribute its seeds? However, there is a theory to explain it.
To begin with, mistletoes want to hide from predators. Possums find their foliage much tastier than that of many mistletoe host plants, and appreciate its higher water content. (In New Zealand, which was possum-free before human interference introduced the pesky beasts, mistletoes which are closely related to the Australia ones haven’t developed the ability to mimic their hosts. Possums have now driven at lest one New Zealand mistletoe to extinction.)
There are some butterflies - jezebels and azures - which lay their eggs on no plants except mistletoes, so depend on them for survival. Perhaps the mistletoes are trying to avoid some caterpillar-grazing as well, though it seems unlikely as butterflies are more likely to find their hosts by their smell.
Meanwhile, it is possible that birds know to look for the host plants, and only when they have found them do they begin to search for mistletoe fruits. This would explain why mistletoes tend to get spread among the same species of host plant even when they can survive on others.
As you might expect, this plant is usually found on she-oaks, though it does sometimes find its way onto Eucalyptus and Eremophila hosts, exploding the myth that mistletoes are unable to thrive on anything other than their most usual hosts.
Needle-leaf mistletoes are pretty plants. The whole plant is covered with pale grey down, and the plum-red flowers, with their bright yellow stamens, emerge from pale velvety buds, retaining this texture on the outer base of the flower. The little fruits are pinkish red.

Saturday, July 17, 2010

Two Felt Ferns

Pyrrosia rupestris and Pyrrosia confluens
This is the “rock felt fern”, Pyrrosia rupestris.
Despite its name, it is just as happy on trees.
I photographed this beautiful plant at Queen Mary Falls (Killarney) yesterday. You can clearly see that the plant is coming into its fertile period, as it has as many of the long fertile leaves as it has little round infertile ones.

The spore bodies on the backs of fern fronds are usually worth a look. Not only are the part of the beauty of the plant, they also help to identify it. In the first place, if you were in doubt, they tell you that the plant IS a fern. Ferns are a very ancient plant type. They evolved long before seeds were even thought of, and reproduce by amuch older method, using spores. No other kind of plant has these brown spore bodies on the backs of its leaves.
The shape and arrangement of the spore bodies also tell you which kind of fern it is.

The rock felt fern has two disorderly rows of round spore bodies.

The spores of its close relative, the “horseshoe felt fern” Pyrrosia confluens make a rather exaggerated horseshoe shape on the back of the leaf-tip.

In the garden, the horseshoe felt fern proves to be almost as drought hardy as the rock felt fern, though in the wild we most often notice it high on rainforest trees. It goes by the rather charming common name of “Poor Man’s Orchid”, and it might indeed be possible to mistake it for an orchid plant, if you fail to notice the spores.
Like the rock felt fern it has two leaf-sizes, but both the fertile and infertile ones are longer.
This is a very easy fern to grow on slabs of tree-fern, or in pots. It excels in baskets where it can cover the structure to make a green shaggy ball. It can also be established quite easily on trees, provided it starts off in a damp shady situation. It is a desirable plant where the landscaper wants to create a rainforest look.
Both these fern are also called “robber fern”. I don’t know why. They are climbers or epiphytes - not parasitic in any way, and steal nothing from the trees they grow on.
(For more on the rock felt fern, see June 2009.)

Deeringia in Winter

Deeringia amaranthoides
I wrote an article on this pretty little understorey plant when the berries first ripened this year, back in May

It underwent its usual leaf-colour change with the first frost - and here it is, in its winter coat. The berries, as you see, are still hanging on, as prettily pink as they were three months ago.

Friday, July 9, 2010

The Lichen Problem

An acquaintance of my husband’s told him, not so long ago, about the problem he was having with lichen at his place. It was, he said, “growing on all the fauna”.

My husband, (after a moment’s astonishment), translated this to “growing on the flora”, and went on to hear the story about how this man had taken his problem to a local nursery, and had been given “some stuff” to kill it.
We wondered, together, whether this story was true. The idea of lichen on plants as a “problem” was a new one to us. We regard lichen as a beautiful ornament in any garden.

We also value the fact that, like a healthy frog population, it is a pollution indicator. Lichens won’t survive if the air isn’t clean. Lichen, in our book, is a Good Thing. It doesn’t harm healthy plants. That a nursery might sell someone a poison to kill it was a mind-broadening concept.

We delight in lichens in all shapes and forms, those “paint blobs” in delicate shades of white, soft green, yellow and orange, that you see on trees and rocks; the leafy-looking encrustations; the growths that cover the soils in the bush; and the preposterous hairy-looking growths that give rainforest trees that bearded look.

Obviously other people like them too, as there is a market for so-called “mossy rocks” - where most if not all of the “moss” is really lichen

Despite their plant-like appearance, lichens are not really plants at all. In fact they’re not even a single kind of organism. They are “associations” between fungi and algae. Some sorts of lichens have several species of each, a little community of friends all happily coexisting and presenting a united front as a lichen “species”.

The alga’s contribution to this team effort is photosynthesis, which provides the lichen’s food. The fungus half of the partnership contributes the structure of the lichen, defining its shape and protecting the algae. It also catches the water, and provides the minerals for the little community.

So is lichen a problem?

To quote the Yates Australia website, (which can be counted on to recommend a chemical for every garden problem), lichens “do not actually affect the health of the tree as they are non-parasitic organisms”.

The lichen which beautifies the dead tree at right was not responsible for its demise.
A few years ago, I noted that the Yates site said bluntly: “There are no approved chemicals for treating lichens and moss on trees and shrubs.”
Now, however, the site has been altered to recommend a cautious use of lime sulphur to destroy lichen on plants, which suggests to me that there has been a substantial body of customers who just can't be convinced that there's any beauty in a thing which finds its way naturally into their gardens.

Are there really people who dislike lichens so much that they would risk damaging their precious plants, to get rid of it?

What about lichen on other substrates?
It forms on rocks, concrete, timber, clay tiles, plastic shadecloth, and metal. Is it a problem?
Lichens do acidify their surrounds, and the acid certainly does, very slowly, erode rocks. The effect is greater where the substrate is damp, and almost non-existent in dry conditions - but in either case is minuscule in the timescale of a human lifespan.

Lichens have been described as “the termites of the plant world”, by those who see them as significant contributors to the long process of turning rocks into soil. However conservators of old British stone buildings and monuments have noticed that old stonework has actually broken down less where it been covered by a coat of lichen than on sections which are lichen-free and exposed to the weather. So it seems that despite their acid production they are not as effective at “termiting” as are frost, wind, and rain.
The same protective effect has been recorded on wood-shingle roofs, and there appears to be no actual evidence of it actually damaging even metal roofs.
Removing lichen does leave ugly marks behind, though, and these are well-nigh impossible to remove.
In all, those who are worried about lichen on their plants and buildings might simply do best to leave it in place and learn to enjoy its beauty.
Then bring on the lichen!How can we encourage it?
Aren’t we humans an interesting lot? While some of us are worrying about how to remove the lichens, others are going to a lot of trouble to acquire it. They want it on their rocks, terracotta and concrete pots, garden structures of various types, buildings, and even on their plants.
The simplest technique is simply to wait. Given an absence of pollution and the obvious lichen-destroyers (garden chemicals, flood and fire), and the presence of nearby lichens as a source of reproductive materials. The Toowoomba district is wonderful for lichen-growing. Long may these conditions last - mining and urban expansion are likely to have their impact in the future.
Many people paint their rocks etc., with various substances to hurry up lichen growth. Popular items are yoghurt, beer, skim milk, thin porridge, rice flour and manure slurry. Healthy lichen is sometimes broken up and added to the mix (or mixed in with a kitchen blender - perhaps not desirable for the manure option).
Results of these techniques have been mixed. Some people get lichen. Some get mosses, or ugly moulds (attracted by the sugars and starches in the slurry). Some don’t care what they get, so long as they’ve made new garden feature look older.
There are three processes involved, when the potions do work.
One is the addition of nutrients. The observation that some lichens grow best where there are bird-droppings has led to the manure slurry technique. (Urine is another favoured ingredient).
The second is acidification. Yoghurt, buttermilk and sour milk are all acid, as well as weak nutrients. They might be a help - or might be a hindrance. There is great variation in pH preference, between species of lichen. They grow on substrates with pH from 4 (quite acid) to 8 (alkaline). If you’re in the know, you can “read” the pH of rocks and tree bark by identifying the species of lichens which grow on them. For the most part, there doesn’t seem to be much justification in using up good yoghurt in the hope of encouraging lichen. The pH you alter might have been just what a local species of lichen really wanted.
An exception is new concrete, which is very alkaline, (pH about 11), and may need active modification before lichen will interest itself in the site. Left out in the weather, the surface of new concrete can drop to around pH8 in five or more years, but adding some sour dairy produce may speed up the process.

The third requirement is some reproductive material from existing lichens. If not included in the slurry, lichens may still be “seeded” from the air, provided there are lichens growing locally.

My own experience, in this district, is that lichen happens.
It needs no help from me, to get established. I am thankful for it, and hope we can all manage to protect the good, clean air that keeps our lichens, our frogs, and us, healthy.

Are Lichens Really Killing Your Trees?

Before blaming the lichen for a tree’s ill-health or death, it is worth considering whether something else is the real culprit.
Dying trees become unable to fight off an overload of lichens, so it can appear that the lichen is killing the trees. (Mistletoes are blamed for killing trees under the same circumstances.) But it almost certainly wasn’t the lichen’s (or the mistletoe’s) fault in the first place.
We humans hate to admit that something we’ve done might be causing our own problems, but with trees, we sometimes kill them despite ourselves.
Common causes of “tree-slaughter” are:
ROOT DISTURBANCE (digging; building; road-making; ploughing)
SOIL COMPACTION (piling dirt higher over roots;  driving and parking vehicles over their root zones: introducing hoofed animals. Life is very tough for any poor tree that finds itself turned into a cattle camp.)
OVER-FERTILISATION (fertilising trees that were previously happy without it; allowing manure and urine from crowded livestock to over-enrich the soil)
DRYING OF THE SOIL (covering soil with asphalt, concrete, or a building; clearing hillside trees thereby causing the water table to drop; installing a bore which can do the same, altering drainage flows with building works)
MAKING THE SOIL WETTER (installing a dam or pond; mulching previously bare soil; altering drainage flows with building works)
ALTERING SOIL SALINITY OR pH. (or adding inappropriate quantities of trace elements)
USING “GREY WATER” (It may be the "grey" that's the problem - or it may just be the suddenly soggy soil)
In our district, the faster our burgeoning population “develops” the land, the more we can expect to have “mysterious” tree deaths from the above causes.
Factors beyond our control may also cause tree deaths. Once-healthy plants can die suddenly from unusually wet or dry seasons, or from new diseases or pests which move into a district.

Some people seem to forget that rather obvious fact. "The tree's been here since my grandfather's day", they say. "I can't understand why it should fail now, after so many years."

But could lichens be causing a problem, all the same?
It is true that lichens can accelerate the decline of aged or unhealthy trees.
This is how they do it:
All bark is dotted with lenticels. These little “bumps” are really openings filled with corky tissue. Oxygen is absorbed through them, and carbon dioxide released, just as it is through our lung tissues. On some plant species these are large and conspicuous. On others you might have difficulty finding them.
Plants need their lenticels for breathing. They absorb oxygen through the pores on their leaves, and through their roots, but this is not enough. Bark (like our skin) is not permeable to gases, but unlike us, plants have no bloodstream to carry oxygen around their bodies. Bark-covered tissues would die of oxygen starvation, without their lenticels.
But then, why don’t lichens always smother trees?
A growing tree is continually stretching and cracking its bark, and lenticels form in the cracks. The same cracks also disturb lichens. It may not look like much, but it’s enough to allow the trees to go on growing, in excellent health, sometimes for more than 1000 years! Some of these trees seem to be blanketed in lichens for the whole of their long lifespans.
Trees continue to grow bigger all their lives, but when they go into decline, or if they’re just not thriving for some other reason, they stop. The bark finishes expanding and disturbing the lichens. At last, they can cover those pesky little lenticels. Lichens that are saturated from prolonged wet weather, or over-enthusiastic use of sprinklers, have the edge when it comes to blanketing ability. It is questionable, however, whether they cause the tree to die any faster than it would otherwise have done.
A beloved, ancient tree might need protection from lichen if it is to go on living, just as it may need other kinds of mechanical and chemical help to prolong its life beyond what nature would have normally allowed.
So what about lichens on younger plants?
Lichen problems on young plants are rare and may even be mythical. If all other possible causes of death have been examined and rejected, and the problem does really seem to be lichen attack, then it might be time to examine whether the species of plant chosen is something that just can’t cope with the native lichens of a particular place.
Some natural environments don’t support lichens. They don’t for instance, occur in places subject to annual flooding, like the Amazon valley, or the flood plains of northern Australia. It’s not unreasonable to theorise that plants native to those places might have problems when we try to grow them in our lichen-friendly part of the world.
Those gardeners who are sure that they do have lichen problems must decide whether the cost, the work, and possible environmental unfriendliness of using chemicals to make war on them is a game that’s worth the candle.
I’d leave them alone. If the problem is imaginary, they’ll live. If the lichen, or some other cause, is killing them, they’ll die.
Perhaps it’s time to let it happen, and move on to planting something that is happy to live where you do.

Saturday, July 3, 2010

Jointed Mistletoe

Viscum articulatum

This mistletoe at Franke scrub is fruiting heavily at present.
It’s a fascinating plant. While it can grow directly on trees, its favourite hosts are other mistletoes. In this case it is growing on Lucas’s mistletoe Amyema lucasii, (Family: LORANTHACEAE) which is growing on a leopard ash, Flindersia collina.

What you see in this photo are the bright green leaves of the leopard ash in the lower part of the picture, the blue-green-leaves of Lucas’s mistletoe in the central and upper section, and the yellow-green branchlets of three plants of jointed mistletoe surround the much larger Lucas’s mistletoe.

Lucas’s mistletoe is in the Loranthaceae, a family with edible fruits that originated on Gondwana. Its various members are still largely restricted to the continents which resulted from the break-up of that ancient super-continent.
The jointed mistletoe, on the other hand, is in the Viscaceae, a family with worldwide distribution. It is quite unrelated to the Loranthaceae, and evolved the mistletoe growth habit quite independently.
The Viscaceae include the classic British mistletoe, Viscum album, of “kissing under at Christmas-time” fame. Our local species, V. articulatum shows its resemblance to V. album, and the various other Viscum species worldwide, but is unusual in being leafless. The white winter fruits of the traditional Christmas mistletoe are an important part of their value as decorations. Our local also fruits in winter, but of course here in the southern hemisphere that means it does it in mid-year .
Viscum articulatum is also native in Asia, where it known as “crabs legs”, and is dried and used in traditional medicine. It is probably not a very safe one, so shouldn’t be experimented with at home.
The fruits of all Viscum species have a reputation for being poisonous, and Wikipedia, informs us that eating them causes “acute gastrointestinal problems including stomach pain, and diarrhea along with low pulse”. Blurred vision and vomiting are other effects reported elsewhere. One of the English Christmas traditions was that a girl who was kissed under the mistletoe would pick and eat a berry for each kiss. A girl who made a habit of hanging around hopefully under the mistletoe could get to eat a few fruits, presumably with no ill effects, since the custom persisted. I wonder whether the English mistletoe species - England’s only mistletoe Viscum album - has a milder effect than other Viscum species? Whatever, the case, nobody should experiment with eating the fruits of our local species!
We can enjoy it as an interesting plant, however, and it certainly provides ornamental foliage contrast in the canopy of the tree pictured.

Bitterbark at the Bunyas

Alstonia constricta
I found this tree growing on the hill called “Little Mowbullan” in the Bunya Mountains. I didn’t know what it was, at first, because its leaves are unusually large, and the foliage unusually dense, for the species. It is one of a group of particularly attractive little bitterbarks.
As you can see, the weeping wavy-edged foliage is very pretty, and the whole made an attractive little shade tree. This is one of the smaller trees in the group. The oldest had a trunk diameter of about 20 or 25cm, and the canopy was about 4m across.
The grey trunk on the older trees was very attractive, looking rather “corky” - but actually very hard.
Flower buds were forming, but we shouldn’t expect the sweet-smelling flowers until midsummer.
For more on this species see Dec 2009.