Conference
1999
New Zealand Plants and their Story
Growing
New Zealand Alpines
Arnold
Dench
27 Lyndfield Lane, Newlands, Wellington
Alpine and rock gardening
in New Zealand seems, to this writer, and other enthusiasts who
have established such gardens, to have received much less attention
in horticultural circles than this particular form of gardening
undoubtedly deserves.
Therefore before moving
to the specifics of the cultivation of our indigenous alpine flora,
it might be helpful for aspiring alpine gardeners if we set out
a number of the advantages of this most satisfying of all garden
pursuits.
The contemporary trends
towards smaller urban properties. For those who wish to utilize
the limited space available to the best advantage, an alpine garden
ensures that "the greatest number of choice and interesting plants
can be grown in a comparatively small space"1.
Many larger properties
with banks or slopes at present covered with ugly and undesirable
weeds, or with a steep lawn difficult to maintain, can be converted
to an attractive rock garden. In this position it is possible to
grow not only some of our choice alpines, but also a range of many
attractive native plants such as flaxes (Phormium
spp.) Astelia spp. and a wide range of small shrubs
like hebes, Leptospermum (manuka) clones, and various unique
New Zealand divaricates.
The hilly or rolling
landscapes of many of our urban areas are ideal for the creation
of truly outstanding alpine gardens.
I can vouch for the fact
that once established, the management and maintenance of an alpine
or rock garden is less laborious and time-consuming than a conventional
garden.
In well-designed and
constructed alpine gardens, plants impossible to grow in ordinary
garden conditions can often be successfully cultivated.
The design, construction
and maintenance of such a garden provides for those seeking some
satisfaction outside the daily routine, "a most beneficial blend
of mental and physical activity"2.
In 1999, the conference
"New Zealand plants and their story" celebrated the contribution
made by Dr Leonard Cockayne to the understanding of our incomparable
indigenous flora. It is therefore appropriate that when considering
what plants to cultivate in our new alpine garden some consideration
should be given to the place of native alpines in the enterprise.
The following words of Cockayne himself may (as in my own situation)
prove decisive in the choice of plants.
"Apart altogether
from that beauty of flower, or of form, which entitles the indigenous
plants to occupy a foremost place in the gardens of this country,
it must ever be remembered that they are peculiarly a New Zealand
production ... they are part of ourselves they are our very
own!" and again "in our gardens, of all the trees or shrubs
or herbs which we cherish, none can ever rank quite as high as those
which slowly took their shape on New Zealand soil in the far distant
past"3.
There have been periods,
when the value of our native plants has been either grossly undervalued
or worthy of serious consideration as desirable garden subjects.
It is also a fact (not alas confined to plants alone!) that our
indigenous flora has been highly valued overseas, but at home almost
totally neglected. This applies particularly to our alpine plants.
Cockayne again "Our flora is famous the world over"4.
Prophetic words indeed, written as they were in 1923! For while
there are many outstanding collections of New Zealand alpines grown
in their country of origin, there is a suspicion that many of the
finest examples of our mountain flora are to be found growing in
northern hemisphere alpine gardens.
Cockaynes' description
of our alpine flora as ... "most precious of all which
dwell near the perpetual snows" has been an inspiration and
a point of origin, not only for many alpine gardeners in this country,
but has been a major influence on the work of many ecologists and
botanists. The late A. P. (Tony) Druce, that incomparable New Zealand
field botanist, freely acknowledged his debt to Cockayne.
For those therefore who
have now decided to become a convert to this branch of gardening,
of which a renowned horticulturist of the past wrote " . there is
no branch more fascinating than the cultivation of alpine plants,
and the management of rock gardens"5, it is important
to realize that certain principles must be applied, and a number
of myths be dispelled if one is to successfully cultivate alpine
plants.
Firstly, let us establish
whether in fact these plants are difficult to grow. I think it can
be agreed that for far too long, gardeners have accepted as a fact
that most of the indigenous flora comes into the "difficult" category.
This is a myth. Cockayne himself wrote, "... it must not be thought
that the majority are not amenable to cultivation. Quite the contrary
is the case by far the greater number yield to the gardeners skill."6.
W. B. Brockie, one time Director of Christchurch Botanic
Gardens and later Curator, Otari Native Plant Museum confirmed this
view "Nearly all of our mountain plants can be successfully
grown in a rock garden ."7. I feel that
some contemporary experts have tended to overuse "easy" in describing
the cultivation of certain indigenous alpines. Perhaps this is merely
a reaction to the long held, contrary viewpoint.
Another myth that needs
to be dispelled is that these plants can be successfully grown by
merely placing some rocks or large stones in a raised bed of standard
garden soil. Much more needs to be done and learned, before one
can claim to have established a viable alpine collection. Brockie
very succinctly summed up what is required in this respect: ".
one of the healthiest of pursuits, and one calling upon the individual
for physical and mental resourcefulness"8.
The first step to successfully
establishing a truly representative New Zealand alpine collection
is to construct ones garden for the benefit of the plants themselves.
It follows from this that some knowledge of the plants'
natural habitats is absolutely essential. It will then soon become
apparent that a diversity of environments or "micro-climates" will
need to be created to satisfy the needs of a variety of plants from
different "alpine" habitats. Rocks strategically placed along with
tussock grasses, sedges, small shrubs, and the application of a
suitable mulch will help greatly the establishment of the new garden.
Secondly, all alpine
plants must have perfect drainage. More failures arc attributable
to poor drainage than to any other factor in the garden environment.
The garden site (which
will be discussed in more detail presently) should be placed where
there is sufficient airflow. Especially in the warmer, low altitude,
humid areas of the country a "cool period" (shady for part of the
day with a good airflow) must be provided, otherwise the plants
ill adapted to such environments will die from heat exhaustion.
The site itself should
if possible be part of the landscape, the more natural the better.
Banks or slopes which are a part of most urban landscapes in New
Zealand, lend themselves particularly well to our purpose. The aspect
should be open and sunny (but see above) and in the warmer areas
a southerly aspect is almost an essential.
The garden should not
be constructed near large trees whose roots will inevitably rob
your alpines of both moisture and nutrients. The overhead drip from
trees during wet weather is a major cause of rot to alpine plants.
Hedges are another menace to the alpine garden as they too rob the
soil of the same essentials.
It will be necessary
to ensure an abundant and constant supply of water. Despite the
remarks above concerning "airflow", care must be taken to provide
shelter (see also above) from the dehydrating effects of strong
prevailing winds, which if salt laden, can cause fatal damage. It
will of course be necessary to eliminate from the site any persistent
or noxious weeds such as onion weed, oxalis, clover, tradescantia
etc.
At this point it is necessary
to state that a flat site can be converted into an attractive and
viable alpine garden. Rock work here is of great importance, but
making such a site part of the landscape is difficult. The bed must
be raised using treated timber or old railway sleepers. Here "perfect
drainage" is much harder to achieve than on a slope or bank.
For those who inevitably
will wish to attempt to grow the "difficult" members of the alpine
flora, and it has to be admitted, a minority of our plants fall
within that category, especially those classified as "choice", it
might be helpful to mention that the construction of a moraine could
give the best, perhaps the only chance of success.
In nature a moraine is
rubble left at the foot of a glacier. It is composed largely of
glacier silt or "rock flour", rocks, shingle and gravel of various
grades. A constant flow of water trickles or sometimes streams through
this material. Such a feature can be constructed in the garden,
either at the foot of the alpine garden, in a gully or as a special
water feature.
It need not be elaborate,
but the supply of water must never dry up. The alpines planted thereon
succeed because their roots are fed by a constant supply of flowing,
not still water. The writer is able to supply detailed information
on request.
It is of the utmost importance
in constructing the alpine garden that the soil or medium in which
the plants are to grow is a mix of those ingredients which will
not only keep the plants alive and growing, but will produce in
due course, the reward of flowers and a supply of seed. Over a long
period I have proved that the following soil "recipe" will guarantee
the desired result.
Brockie called this mixture
his "scree material" and the proportions of ingredients should remain
constant and notwithstanding the size of the garden, the depth of
the mixture in which the plants are to grow should not be less than
30 cm.
"To three barrowloads
of . quarry waste, add three barrowloads of quarter-inch road metal
and two barrowloads of sieved leafmould. If leafmould is not available,
use the same quantity of fibrous loam . These ingredients should
be thoroughly mixed together"9. As fibrous loam
may not readily be available, a satisfactory substitute would be
good quality peaty compost. To this mix may now be added with some
caution, either a proven slow-release fertilizer, boneflour or dolomite
lime in combination or as a single additive.
After construction, the
garden should be given a settling down period of some weeks. This
allows the soil mixture to consolidate, with no damage to plant
root systems when the alpines are set in place, and also allows
quick growing weeds to emerge and be removed before planting begins.
Plant out the alpines
in the period late autumn to early spring when they are just beginning
new growth. Losses will occur if the plants are unable to establish
a vigorous root system before dry and warm weather arrives.
All alpine plants must have
a cool root run to survive, and as not all the plants can be placed
close to a large rock under which their roots will penetrate and find
the required cool dampness they need, another method must be found
to provide a substitute.
By far the best solution
is to cover the entire area of the new garden with a mulch consisting
of small rock fragments and stones of various sizes combined with
a selection of road metal laid to a depth of about 5 cm. I collect
so called "quarry waste" from a local quarry and have found that
this material as well as looking "natural", gives really outstanding
results.
I find maintenance of
the alpine garden far less onerous than is the case with border
or perennial beds. Once the scree has settled, small weeds appear
from time to time, but are easily removed. An annual top dressing
of the alpine garden is absolutely necessary, and is best carried
out in the autumn. I use bone flour mixed with heavy sand, but success
has also resulted from using leaf mould (if you are fortunate to
have it) or a good organic compost in place of the bone flour.
For the more difficult
or choice plants, only sand or gravel mixed with a little good soil
should be used. Do not heavily top dress; a covering annually of
about 1-2 cm is adequate. Do not apply artificial manure of any
kind as this will result in unnatural coarse growth and more likelihood
of disease and insect attack.
I believe it appropriate
to conclude this article by quoting some words of Cockayne himself,
and although these words were penned as long ago as 1923 they are
just as relevant today. All those wishing to establish a garden
for alpine plants should heed them.
"Even in New Zealand
itself, strange as it may appear, there is no place where every
indigenous plant can be cultivated. Certain localities specially
favour alpines in others these grow either not at all, or with the
utmost difficulty"10.
There are of course those
gardeners who will still wish to grow alpines despite the unfavourable
environment in which they are to be grown. These people are the
real enthusiasts of the alpine gardening world, and with the application
of some of the principles outlined in this article, some limited
success may well indeed be achieved, but as Cockayne put it "the
difficult will always remain the business of the enthusiast"11.
In my own case, many
have been the failures and disappointments encountered on the way
to establishing a viable collection of New Zealand alpine plants,
but great indeed is the satisfaction, when one at last achieves
even a modest success. I do not know of any other branch of horticulture
where ones endeavours are better rewarded.
References
1Tannock,
D. 1924: Rock Gardening in New Zealand. Whitcombe and Tombs Limited.
Introduction, p.5.
2Brockie,
W. B. 1945: New Zealand Alpines in Field and Garden. The Caxton
Press. Introduction.
3Cockayne,
L. 1923: The Cultivation of New Zealand Plants. Whitcombe and Tombs
Ltd, p.8.
4Cockayne,
L. 1923: The Cultivation of New Zealand Plants. Whitcombe and Tombs
Ltd, p.8.
5Tannock,
D. 1924: Rock Gardening in New Zealand. Whitcombe and Tombs Limited.
Introduction, p.5.
6Cockayne,
L. 1923: The Cultivation of New Zealand Plants. Whitcombe and Tombs
Ltd, 1923, p7.
7Brockie,
W. B. 1945: New Zealand Alpines in Field and Garden. The Caxton
Press. Introduction.
8Brockie,
W. B. 1945: New Zealand Alpines in Field and Garden. The Caxton
Press. Introduction.
9Brockie,
W. B. 1945: New Zealand Alpines in Field and Garden. The Caxton
Press. Introduction.
10Cockayne,
L. 1923: The Cultivation of New Zealand Plants. Whitcombe and Tombs
Ltd, p 11.
11Cockayne, L. 1923:
The Cultivation of New Zealand Plants. Whitcombe and Tombs Ltd,
p 11.
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