Re: disappearing Angophora costata
- To: m*@ucdavis.edu
- Subject: Re: disappearing Angophora costata
- From: J* A*
- Date: Mon, 07 Aug 2000 13:47:34 +1000
At 20:30 Sunday 6/08/00 +1200, Moira wrote:
Richard Starkeson wrote:
>> Our local paper the Chronicle (derogatively referred to by the natives
>> as the Comical) had a 3 line item in it today about the disease and
>> death of virtually all of this tree in the vicinity of Sydney.
This is a slight exaggeration, to say the least. Not many trees have
actually died, at least not yet. But there's been serious dieback.
>> I have
>> not seen the tree, but it is known for its attractive smooth bark. Does
>> anyone in that part of the world recommend it as especially attractive?
>> Flowering display? Is it really headed down the road to near
>> extinction?
> Agophora costata (Smooth Barked Apple or Sydney Red Gum)
> in my Australian Wildflower Catalogue this relative of the Eucalypts
The genus Angophora has always (well, as far back as I remember) been
separate from the genus Eucalyptus. You may recall that a couple of years
ago, the splitters got busy and chopped Eucalyptus into three or four
different genera. Well, a few months ago the lumpers struck back, so
Eucalyptus now not only contains all it did before, but has also swallowed
Angophora. So I guess it's now Eucalyptus costata, at least for the moment.
> is described as "a beautiful specimen tree for its interesting form, but
> only suitable for the large garden or park".
Well, I've got one in my backyard in inner-city Newtown, which is 3.5
meters across (the block, not the tree). OK, the tree actually covers two
or three of my neighbours' backyards as well. I planted it in 1975. It
has not been all that vigorous a grower after the first ten years (several
big branches died), perhaps because the soil there is too fertile, or
perhaps because of the pollution.
> It has large clusters of snowy white flowers very similar to those of a
> gum tree.
and interesting twisted branches.
> It needs some protection from strong winds because of brittle wood
Around Sydney, it often grows in very exposed coastal positions, often the
only trees that will grow there -- rooting in narrow cracks in the
sandstone rocks and forming beautiful windswept specimens a few meters high
with trunks a meter or more across.
But yes, like many eucalypts, it does tend to drop big branches, especially
(but not only) in unusually high winds.
> and also from frost when young.
Hmm. It certainly grows prolifically in the sandstone parts of the Blue
Mountains west of Sydney, where there are quite heavy frosts for several
months of the year, as well as the odd snowfall. If it's frost-sensitive
while young as you say, I guess it must be one of those eucalypts which
don't germinate till the spring after they flower, so that the seedlings
are well along by the time they encounter their first winter.
> For average gardens there is apparently a smaller species (A hispida)
> known as the
> Dwarf Apple) described as a spreading shrub or small tree with the young
> growths and flower buds covered with velvety red hairs. When the flowers
> open they are white and showy and they are followed by ornamental seed
> capsules.
Of the many (at least 20?) species of Angophora ("apple gums"), all (AFAIK)
have the same interesting twisted form, but almost all have rough bark
rather than the smooth shiny bark of costata, with its beautiful colouring,
especially when the old bark has just been spread. I believe there is one
other smooth-barked species, which grows further out west in NSW. Is this
A hispida?
> The disease which is destroying these trees evidently became apparent
> later than 1987 when this book was published, as there is no mention of
> any problems with growing them. In fact the dwarf species is described
> as "resistant to disease and pests"
Yes, it's a very recent occurance. I've only heard about it on a radio
program a couple of weeks ago (half an hour or so on it, so better than
Richard's three lines :-). It wasn't clear to me from what they said
whether the problem is only hitting trees within the Sydney metropolitan
area, or whether it has also been detected in trees in wilderness areas
well away from urban runoff etc. So far they have no idea what might be
causing it, they're still at the data-collecting stage. If it's restricted
to trees in and near the suburbs and agricultural areas, one obvious
possibility is some fungus etc that maybe was always there, but which does
little damage except when trees are weakened because soil conditions have
changed -- for example due to added nitrogen or phosphate -- the Sydney and
Hawkesbury sandstone country is notoriously low in phosphates. As Moira says:
> Phytophthora species are well-known killers of a number of different
> trees throughout the world, but I think the majority do not usually
> attack fully-healthy trees but rather those weakened by stress,
> including such things as poorly-drained soils.
John.
