Re: P. radiata disease and other matters

Bracey Tiede wrote:
> I have learned in my Master Gardener classes that the initial factor
> in Pinus radiata decline is Pine Pitch Canker which arrived in
> California recently (1986 in Santa Cruz).  This fungal disease
> weakens the tree and the borers move in for the kill.  There is a
> task force dealing with it at http://frap.cdf.ca.gov/pitch_canker.
> You can see the spread of the disease on the site.

I am sure our NZ Forest Service is well aware of the havoc these
problems would cause in one of our major export industries and are working strenuously to keep them out. They have done well so far and we certainly hope they can continue to keep our trees healthy.

> Tree topping will definitely weaken a tree as well and P. radiata is
> also a very fast grower resulting in weak limbs that split and fall.

P radiata is rarely planted here as an ornamental these days. In
suburban situations at least its rapid growth can make it quite
overwhelming and incur the wrath of neighbours when it steals their sun
or falls on their roof in a gale. One problem is that seed can spread
around and wilding pines do from time to time appear in gardens and in
regenerating native forest or in wild grassland in the High Country,
where they are less than welcome. In  gardens especially, owners with
little horticultural knowledge or interest often  leave them be until
they suddenly realize they have a serious problem, by which time
removing them is both very difficult and highly expensive.

One place where however the species is cherished is in The Wellington
Botanic garden, which is the curator of the original strains imported
in the 19th century as a seed source for the proposed industry. These
strains are still preserved as far as possible as they could still form a useful gene pool should any severe problems arise in the forests, but
reproducing them is now matter of urgency, as most are approaching the
end of their useful life and though some specimens have already lived to
nearly 120 years they are definitely becoming senescent and harder to
reproduce.

This comparatively short lifespan is I guess typical of a conifer (or
any other species) which is naturally fast growing. Most of our native
Gymnosperms here are quite slow in comparison, but likely to live on average five or six times as long, while the king of our forests, the noble Kauri, can last more than a millennium (as I believe is also true of North American Redwoods).

As a nation, Kiwis are real bad, where trees are concerned, at planting
species too big for the property and then not even merely topping them to fit, but mutilating them further by wholesale cutting back of large
limbs, with no attempt to leave a side branch at the tip -just a hideous
stump-. This often seems to he done without rhyme or reason almost as though they either hate or fear the tree and all too often leads to the entry of diseases. In the course of pruning professionally I have several times been approached to perform such drastic surgery, but when questioned, the owners almost always admitted the tree was not actually causing any problem of shading or suchlike. The owner of one garden said vaguely she thought all trees needed to be cut from time to time! (the victim I saved in this case was a handsome and not overwhelming Liquidamber well away from the house and the neighbours. Fifteen years later I am pleased to note it is still standing unharmed..

I will say the majority of these sad trees have been mistreated strictly by their owners. Although there are still a few "tree fellers" around, (with no more clue than their customers) who would do the same, the major professional operators are all properly trained arborists, with skills like thinning and crown raising, which will deal with most problems and prevent the formation of what one South Island professional liked to refer to as "Arbor decapitata". He had, I remember a horrific collection of images of these unfortunates and a passionate lecturing style!

Moira
--
Tony & Moira Ryan,
Wainuiomata, North Island, NZ.     Pictures of our garden at:-
http://mywebpages.comcast.net/cherie1/Garden/TonyandMoira/index.htm
NEW PICTURES ADDED 4/Feb/2004

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