Re: Wind
Larry Harris wrote:
>
> There is another factor to be considered in the case of wind. The direction of the wind as it comes on to the land.
Well, I guess my part of New Zealand is at least Mediterranean in its
latitude (Wellington, only a few miles away, being the antipodes of
Madrid), and also in its basic climate, with most of the rain in winter
and reasonably hot summers. However, the climate is modified to some
extent by our close proximity to the ocean (not merely a land locked
sea, such as southern Spain) and by the exposure to the Roaring Forties,
the strong westerly winds which blow almost without any check round and
around the southern ocean. We are particularly aware of them locally,
because the adjacent Cook strait (separating our two main islands)
funnels the blast so "Windy Wellington" is not just a joke. Around the
equinoxes (and especially in spring) we normally get winds which other
parts of the world would classify as severe gales, but both we, our
buildings and our vegetation are so used to them that it is only when
they actually reach storm force and start blowing roofs off that they
may merit a comment on the news. We also from time to time get a fairly
strong cold wind from the south, but this is more prevalent in winter
and is also commonly rain-bearing, so its effects are usually less
drastic.
One thing which makes the westerly winds easier to cope with is that
they tend to blow straight and relatively steady and we are fortunately
outside the latitudes where twisters and cyclones normally occur.
Gardeners here, unless in very sheltered positions, do have to take the
yearly "windfest" into account in their designs and there are a nunber
of approaches. The obvious one is to provide shelter, by such things as
creating strategic banks and making thick plantings of wind-resistant
protective shrubs or trees. In an adjacent farming district almost every
large paddock is separated from its neighbour by a shelter belt of
large trees such as pines or cypresses. In recent years there has been a
noticeable trend where such belts have needed renewal towards much more
mixed plantings, which are better at filtering out such things as ground
draughts.
Another approach with exposed garden sites is to use the native species
which are naturally adapted to wind (there are many here, as can be
imagined) and such plantings can also include wind-tolerent species from
other parts of the world (many of the South Africa Proteaceae for
instance perform exceptionally well, provided one can give some
protection from wind-rock by the judicious placement of
rocks).
In really exposed positions, such as the western seacoast, the taller
elements of even the natural vegetation (leathery-leaved evergreens)
suffer a yearly wind pruning on their exposed sides and develop with
time a lean away from the west which often resembles a careful piece
topiary.
In gardens the abilty to successfully survive and withstand the full
force of the wind is undoubtedly always linked with the evergreen habit
and with a tough resistant cuticle. Even Camellias, for instance, can
sometimes be surprisingly successful in coastal gardens provided they
have a cool, well-protected, mulched root run, as they tend to do most
of their flowering at time when the winds are relatively moderate. Even
quite finely-divided leaves can cope if they are also tough rather than
soft and that includes a munber of pines and other conifers and also
Casurinas and many wattles.
Of native NZ plants several species of Coprosma, most of which grow
naturally in exposed coastal positions, and the broadleaf (Griselinia)
come easily to mind as among the most wind tolerent. Many Hebes come in
this group (H speciosa for instance is originally a seacliff plant). In
mostly frost-free areas the spectacular Pohutukawea tree (Meterosideros)
with its brilliant scarlet myrtle blooms is totally resistant to coastal
storms, often growing wild on the most exposed seacliffs. And one must
not, of course forget the NZ flax, one of whose species (Phormium
cookianum) grows naturally on cliffs around Wellington harbour.
In my career as a horticulturist I once had a garden to deal with which
surely must have been the windiest in all windy Wellington, lying on a
hill top at the head of a valley running up with little obstruction
straight from the west coast. On bad days it was not difficult to be
blown off one's feet if coming sudddenly into an exposed area. Because
of its situation and the lie of the ground it was only possible to find
tiny patches of shelter, which allowed the growing of a few non-coastal
perennials, but otherwise experience showed just about everything needed
to be totally windproof. I very soon learned to eliminate any dreams of
growing any sort of deciduous shrub or tree and even among the
eveergreens careful choice had to be made.
To start with I tried for instance to establish a deciduous speciment
reee (a small copper beech which the owners had brought from a previous
garden). There was one lawn which looked promising, with a building to
the west, which I hoped might give a sufficient wind shadow. As it
transpired the wind blew both over the building and round it to the
north, and after entirely losing two suits of leaves to windburn in its
first season the unfortunate little tree gave up the struggle and was
later replaced by Cedrus atlantica which did manage to survive
reasonably well.
One of the problems of providing shelter on that site was that it would
have necessitated finding some way of erecting a filtering barrier of
considerable height both on the west and on the north. Being right on a
hilltop, to do this effectively for more than a tiny area would have
needed shelter at least 3 or 4 metres tall, which could not be achieved
quickly nor without considerable expense. There was the added
complication that in the southern hemisphere north and west are the two
principal directions from which a garden receives its sun, so the deep
shading which would result would in turn limit what could be grown.
Well, by trial and error over several years I did eventually find plants
which could not only survive but look good. Aloes (typical Med plants?)
were a considerable success, a large clump florishing on a bank at the
extreme NW corner below a Coast Banksia (B integrifolia) which seemed
quite unperturbed by the constant blast.
One interesting site was a flowerbox running the full width of the
building across its front between basement rooms and the main house.
This was facing due west and even keeping soil in it proved to be a
struggle until I introduced a mulch of quite sizeable pebbles to keep it
down. I filled the box with a whole selection of succulents, such as
Echeveras, Cotyledon, Sedum and many others, interspersed with clumps of
scarlet Nerine fothergilli. The succulents were in every colour I could
find including green, gold, lilac, blue, scarlet and orange and really
looked quite beautiful together when they had spread and mingled. They
suffer the wind at all times and never get watered, except by rain, but
even after more than ten years of such total neglect they were still
looking good when I visited last year.
My own garden lies in an approximately E-W valley, but is partially
protected by a fairly distant hill to the NW and also a high ridge
immediately to the south. When we first lived here 45 years ago the
valley floor with the new sub-division had been farm paddocks and was
distinctly short on trees. There were also no other buildings west of
us. (we were in effect pioneers)
Now the valley upwind is filled with houses and their attached gardens
are full of quite large trees. This combination of randomly-placed
buildings and trees of all sorts of sizes has led to an astonishing
diminution in the degree to which wind affects us. Even our most exposed
bed, a North-facing terrace on the hill behind us is really not that
much affected any more, though it is still planted in wind-resistant
plants including proteas, lavender, cistus Ipomaea mauritanica and bush
marguerites interspersed with some Mediterranean Narcissus species and
other tough bulbs like grape hyacinths.. It will also happily grow such
South African species as miniature Agapanthus, Babianas, Ixias and
Sparaxis, though to my surprise I have had little success with Nerines,
which keep on dying out on me.
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand. (on the "Ring of Fire" in the SW Pacific).
Lat. 41:16S Long. 174:58E. Climate: Mediterranean/Temperate
