Re: New Zealand Flora

Deborah Lindsay wrote:
> 
> On March 4, '99 Moira wrote:
> 
> "There are two characteristics of the NZ flora which tend to make
> all-native gardens distinctive, one is the paucity of herbaceous plants,
> including bulbs, and the preponderence among them of white flowers, and
> the other is that virtually all trees and shrubs are evergreen."
> 
> Moira (and others),
> 
> I found this an interesting observaton and wonder if anyone knows (or has an
> educated guess) why these characteristics exist in the NZ flora.
> 
Hi Deborah 

The key to NZ's unique flora and fauna can be found in two facts -its
very early separation from Gondwanaland and its subsequent almost total
isolation until the coming of the Maori around a thousand years ago..

As a result of the early isolation its original flora was mainly what
are now considered archaic species (which also occur to some extent in
Tasmania and South America,  Notofagus spp, for instance) and one can
suspect that the largely evergreen habit is related to this. Presumably
at that time Gonwanaland had a sufficiently equable climate that the
deciduous habit was unnecessary and even though these islands
subsequently went through  glaciation there was apparently not a large
enough genetic base for the deciduous habit to generally develop. During
the cold times almost the entire flora which survived  seems to have
done so by retreating to a few refuges, reoccupying its main territory
as warmer conditions returned.

Due to continued isolation as a sea island the indigenous flora we see
today is simply  this original "kitset" and its subsequent modifications
over time.

As to the low proportion of herbs, almost the entire land surface apart
from alpine regions and seacoasts was generally occupied until human
times by a continuous cover of dense temperate  rainforest, and this
leaves little space for anything but trees and lianes and perching
plants with an understory mainly composed of ferns, mosses and their
close relatives (of which there are a great number of species).

There are a lot of herbs in today's flora which  have come to occupy
many niches since a large part of the forests were cleared, but almost
without exception these have their origin in Britain, Australia or other
places from which the European settlers brought their crops, having
hitched a ride with imported plants.

Turning to the preponderence of white flowers. I think this largely
reflects to composition of the original insect population and possibly,
as in the case of the trees, its ancient origins. Anyway, there are lots
of moths, but extremely few butterflies and those are mostly variants on
a couple of types - a blue (which can also be copper) and a small
speckled orange, both of which have divided into numerous species. There
are also a few  small native bees, all solitary, and various flies which
may act as pollinators. As you may know, moths are mostly night fliers
and depend not on colours but on the whiteness of petals showing up in
the dusk or in moonlight. A very few alpine flowers are blue or have
blue markings which may suggest bee-pollination.

We do however, have a few plants which go against this trend very
strikingly. Most notable are a tree, the Kowhai (Koh-fie) - Sophora
tetraptera - and another more variable relative which has several
shrubby forms. All these have large showy clusters of golden peaflowers.
Another is a shrub, the Kaka beak (Clianthus puniceus) which has sprays
of large scarlet peaflowers and a third is the NZ flax, a large clumping
liliaceous plant with sword-like leaves, species of which have tall
stems bearing clusters  of striking red or yellow flowers. Those of you
who are familiar with nectar-feeding birds will recognise what
pollinates this group of plants. We have several of our own unique
species of nectar feeders here which make good use of these plants, but
also now have widened their diet to include suitable introduced species.

Finally we have an example of a unique growth habit in certain
not-necessarily closely related shrubs. These start life in a
divaricating form and build up a bush in which all the shoots divide and
divide, giving them their common name of Chickenwire Plants. Suddenly,
however, when they reach a height of around a couple of metres they
change to a normal adult form. This curious habit has puzzled botanists
a lot and they have come up with one ingenious explanation. Before the
Maori wiped them out the "grazing animal slot" in our bird-dominated
fauna was occupied by several species of Moa (a group of birds related
to the ostrich). It has been suggested that the divaricating habit
allowed the plants to successfully resist moa grazing!!!

I have taken the liberty of cross posting this to Organic Gardening, as
I thought it might interest my friends there also.

Moira
-- 
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, 
New Zealand (astride the "Ring of Fire" in the SW Pacific).
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