Re: Lifespans
Richard and Bracey Tiede wrote:
>
> I am searching for information on the 'average' lifespans of trees and
> shrubs and perennials that are typically planted in mediterannean climate
> gardens. For instance, I had heard 'somewhere' that ceanothus typically
> live for 10-12 years. Any assistance would be appreciated. My searching
> has turned up bits, but nothing for more than a single species.
>
Bracey
As you will have gathered from several replies your question is a bit
like the classic "how long is a piece of string".
A few pointers though. There are at least two distinct classes of woody
plants, those which rocket up and like a rocket fall to earth just about
as quickly (say after between 10 and 20 years) and those which plod
along but keep on going almost indefinitely (from a hundred years to
even a couple of millenia). So basically one can generalize the slower
it grows the longer it is likely to last.
In the "rocket" group (Most of which would not normally last more than
10-20 years at the outside) I would place a number of leguminous trees
and shrubs, such things as Acacias, Virgilia, and most types of broom,
also the Ceanothus you have already mentioned together with Cistus and
other rockroses, Hebes and many lavenders. Commercially, at least in NZ,
peaches and nectarines would fall in this category and even in gardens
they don't really produce successfully that much longer unless very
cunningly pruned.
The length of life in this group is also very much influenced by growing
conditions and, unlike what many people would presume, those which have
the hardest life are often likely to last the best. Rich soils and
excessive moisture (particularly during summer) distinctly shorten their
useful existence mainly by encouraging unnnaturally lush sappy growth.
However, with such things a lavenders, Ceanothus, Cistus and Hebes
judicious pruning after flowering NOT accompanied by feeding will often
prolong life by encouraging new vigorous and healthy shoots and
minimising the proportion of old wood. However some at least of these
plants can be easily renewed by cuttings or layers and this is often
more profitable than struggling to keep the original plant going past
its best.
Many people also find members of the Proteaacea only last a few years in
their gardens, but I have a Protea cynaroides which has flourished on a
sun-facing bank in my garden for close on 45 years and is so vigorous I
had to give it a good cutback recently (not its first) as it was
overwhelming its neighbours. It annual crop of 40-50 huge heads is quite
spectacular.
And what is the recipe for its success? Very simply almost total
neglect; apart from deadheading and those occasional trims it is
entirely left alone. It is planted in a stony bank, and when itwas young
large boulders were placed around the root, and that is precisely all
(no feeding and no watering apart from what nature provides).
Turning to the other group, which one might call the "survivors"
although even they vary in length of life quite considerably, from your
point of view almost all of them could be expected to outlive you, so
their actual lifespan is pretty academic.
This group includes the vast majority of temperate deciduous trees and
some of their evergreen relatives (oaks, for instance). Unlike the first
group many can take plenty of moisture and quite rich living, though one
should not overdo this and it certainly will not suit some species from
the Californinan and European Med areas (Live and cork oaks for
instance), which have a distinctly specialized lifestyle. If correctly
treated most will usually live several hundred years..
Comparatively short lived trees I can think of in this group include
ornamental cherries and Japanese plums (30-40 years on average), but
pears and apples will usually outlive their first owner. I am not sure
how being on dwarfing stocks might influence lifespan, but I have
healthy dwarf pear and apple varieties which are over 40 years old and
still producing mightily.
If the evergreens in this group, Camellias can live several hundred
years (if they don't succumb to poor drainage) and you may reasonably
presume they will at least last you out. Many Rhododendrons are also
very long-lived. Pieris, I am not sure, but probably the same.
I was interested in Alessandra's information that stone pines typically
live about a hundred years. I wonder if this is characteristic of the
genus, as Pinus radiata (the main commercial timber tree in NZ) if not
cut in its prime seems to have a natural lifespan of between 100 and 120
years while other conifers, such as the redwoods and the NZ Kauri think
nothing of a thousand or even two thousand years. I do find though, that
several conifer cultivars, mostly species of chamaecypais I think, do
not last well in our local climate (modified Med - more summer rain).
After fifteen years or so they become increasingly loose and untidy and
often suffer from stem cankers, leading to nasty brown dead patches in
the foliage. I don't think cypresses either are as long-lived here as
they evidently are in Italy.
I am afraid it is not possible to be more definite. I think one gsts a
feel after a while for what is likely to last and what is more likely to
be merely a "rocket". I don't think anyway one should go entirely for
survivors. A garden without change can be rather unattractively static
and a few passing "rockets" are good to liven things up.
As to perennials, with many of these treatment also has a lot to do with
survival and a number of particularly the mat-forming kinds can best be
kept healthy by regular (say evey second year) lifting, the application
of compost to the site and the replanting of only the most vigorous
pieces from the ourside of the clump. Those which do not spread in this
way can also profitably be renewed from cuttings or layers. There are
few perennials I think which are likely to flourish on total neglect,
however I cannot speak for all kinds.
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata (near Wellington, capital city of New Zealand)
