Ferns
in the Garden
Ferns
are often undervalued as landscaping plants. They can be ideal
for filling a dark damp south-facing corner that seems to defy
any other type of planting. They can also be useful under decking
or raised porches, so long as adequate irrigation and drainage
are provided. Ferns suitable for garden use cover a wide range
of sizes, from tree-ferns such as Cyathea to the myriad
smaller species, such as Blechnum, Polystichum,
Davillia and Nephrolepis, for underplanting.
Protection
from climatic extremes is the essential ingredient in successful
garden cultivation of ferns. We've all observed their natural
habitat in our forests, clustering together in deeply-shaded gullies,
close to permanent water. Similar conditions should be found or
created in the garden when considering growing ferns.
Protection
from the sun should be provided by planting ferns under the shade
of evergreen trees, taking care to account for the varying angles
of sunlight throughout the seasons. They can tolerate a dappled
light or a period of morning sun, but most species will burn if
exposed to the midday or afternoon sun, especially in warmer parts
of the country. A tree canopy will also protect less hardy ferns
from frost. In cooler areas, some hardy frost-tolerant varieties
can be planted under deciduous trees, allowing exposure to the
weaker winter sun.
Wind
is the other great enemy of the garden fern, causing both physical
damage to the more delicate species and accelerating the drying
out of fronds. A position protected from winds should be found,
or, if necessary, such protection should be provided by surrounding
plantings or structures such as trellises.
An
effective irrigation system and good mulching practices can allow
ferns to cope better with these stresses. A permanent watering
installation is best, rather than relying on the vagaries of hand-watering,
and fine misting will help maintain a suitable level of humidity,
slowing the drying process. This is one situation where a moisture-sensing
controller is most beneficial, automatically varying the watering
rate according to the level of ambient humidity, temperature and
air movement. Like most plants, much more water will be transpired
with hot summer winds blowing, while plants are growing at their
maximum rate and sending out tender new fronds, than during periods
of winter drizzle when they are relatively dormant.
Another
means of raising the humidity is to group ferns around a pond.
Ferns naturally congregate near water, and they help such landscaping
look more natural, while enjoying the benefit of the air moisture
given off by evaporation.
The
ideal soil for ferns would be a slightly acidic loam rich in organic
matter, though most will tolerate heavier soils so long as steps
are taken to improve the drainage, such as the digging in of quantities
well-rotted compost. For most species, soil should be slightly
acidic. If the pH measures on the alkaline side of neutral after
plenty of humus-which should itself be slightly acidic anyway-a
further increase can be achieved by adding sulphur in forms such
as iron sulphate or chelates or aluminium sulphate, normally sold
as a blueing agent for hydrangeas. This preparation should be
undertaken before planting so the ferns may grow undisturbed once
established.
Mulching
is another key to success with ferns, imitating the natural environment
of the forest floor where leaves constantly drop from overhanging
trees, adding to the surface layer of decaying matter. Ferns are
shallow-rooting and a good layer of mulch will help retain moisture
around the roots as well as maintaining a more even temperature.
Mulching will also help suppress weeds, allowing the soil and
the fragile roots to remain undisturbed.
The
natural diet of ferns is provided by this organic matter breaking
down slowly, and this, too, is the best way of feeding garden
ferns. A totally organic mulch is best-garden shreddings, old
leaves, or any organic matter, along with an occasional sprinkling
of blood and bone or well-decayed compost. The fernery is also
a good spot to empty the tea-pot, but make sure the water's cold
before you do so! Avoid any strong chemical fertilisers when feeding-choose
a slow-release pellet variety such as Osmocote® if you must
use a chemical type. Don't apply any fertiliser too close to the
plants to avoid the risk of burning-instead, scatter it onto the
surface of the mulch and allow it to break down and filter into
the soil naturally with watering.
Along
with mulching, consider a suitable ground-cover as a living mulch-the
native violet, Viola hederacea, works well amongst ferns.
Ferns in the home
Ferns have long been a popular choice of house plant and for
just as long have found their way into the dustbin, having died
a few months-or less-after being brought into a totally inappropriate
environment.
Most of the many varieties of Boston fern, Nephrolepis exaltata,
seem to be able to survive just about anything thrown at them,
so these have rightly taken pride of place as the most popular
indoor fern. I have an ancient basket-borne Boston that lives
close to the ceiling in the heady warmth generated by a wood
heater-definitely not ideal conditions-and it thrives with its
healthy fronds over a metre long and requiring division every
year. Other more delicate ferns, such as the beautiful maidenhairs,
Adiantum species, that so many have aspired to grow, will surely
fail in most domestic environments unless specific steps are
taken to improve growing conditions.
Lack of adequate humidity is usually the main problem, caused
by our natural human desire for warmth. Heating systems cause
the air temperatures and humidity to fluctuate unnaturally. Plants
growing in such conditions will be more susceptible to attack
from mites and other pests.
There are several ways that these conditions can be improved.
One is to group plants together, either several in a larger container
or clustered in their individual pots. Place the pots in saucers
or bowls of water with scoria or some other absorbent material
so the plants may benefit from the humidity gained as the water
evaporates.
Take the plants outside occasionally to 'freshen up', particularly
during periods of gentle rain or drizzle, or at least give them
a light hosing to wash off dust. Periodic use of a misting spray
is also beneficial in maintaining humidity.
Feed indoor ferns sparingly-liquid or slow-release fertilisers
are ideal, and there are a number of types specifically marketed
for use on ferns. A smaller quantity more frequently applied
is tolerated better than the doses recommended for normal houseplants.
Feeding should only take place during periods of active growth,
but if the house is well heated during winter, this period may
be continuous, as with the long-suffering Boston fern I mentioned
before. As a rule, feed when you can see new fronds uncurling.
Container-grown ferns will need periodic repotting, and, with
good growth, this should be at least every two years. This provides
an ideal opportunity to tidy up and divide the plant, removing
and replacing excess potting mix.
Commercial general-purpose potting mixes are quite satisfactory,
though some may benefit from additional coarse sand to improve
drainage.
Pests
Ferns are most susceptible to attack from a variety of enemies,
both indoors and in the garden, during active growing periods,
when the tender and tasty young fronds are uncurling. The new
growth is distressingly vulnerable to complete removal by snails,
slugs, caterpillars and beetles, all of which can be controlled,
to a degree, by good management and chemicals, preferably weak
and organic.
Snails and slugs will resist crossing some mulches, such as
sawdust or wood shreddings. Aphis and caterpillars can be hosed
off or sprayed with Pyrethrum. Mealy bugs and scale can also
enjoy sucking on the tender young flesh of ferns, and the most
effective approach to these is a weak solution of malathion and
dilute white oil. Take care, as too heavy a concentration on
particularly tender ferns, such as maidenhairs, can kill the
plant as effectively as the pest.
In an enclosed environment, such as indoors or in a glasshouse,
the dreaded two-spotted mite, also known inaccurately as 'red
spider', can wreak havoc as it can with any house plant, and
this is best controlled by increasing the humidity rather than
any synthetic approach.
These almost invisible predators prefer dry conditions and ferns
generally don't, so, given the right environment, mites should
remain in check.
Species
Winds have carried the fine spore of ferns across the globe
with great efficiency, with the result that members of many genera
can be found on several continents. There are some 10,000 known
species, including over 350 Australian natives, so I'll take
a brief look at a few you may come across, and leave the rest
to the reference library. The suitability of fern species for
garden or house plant use will vary widely according to local
conditions and the origin of the species being considered, so
it's hard to specify lists for particular applications. If growing
native Australian ferns, it's obviously safest to select from
those species originating from your own area. Remember, of course,
that it is illegal to remove ferns, or any other native plants,
from any crown land.
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Dicksonia antarctica |
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Dicksonia antarctica in the Otway
Ranges, Vic. |
Tree ferns
These distinctive ferns assume grand proportions in the wetter
forests of Australia and New Zealand. The best-known and most
commonly grown is Dicksonia antarctica, the soft tree
fern, found in gullies along the eastern seaboard from southern
Queensland to Tasmania.
Like other ferns, they can be propagated from spores, but it
takes, of course, many years for the plant to reach sufficient
size to be useful as a garden plant. Instead, they are normally
harvested from the bush by sawing the trunk at ground level,
with the subsequent forlorn stump being planted to one-third
its length in its new site. They are very tolerant of such abuse
and are often seen thriving even in full sun, although their
new location will surely lack the tranquil serenity and lushness
of the original habitat.Tree ferns have usually taken many years
to reach the height at which they are harvested, and, despite
the fact that there are already strict controls on their harvesting,
one has to question the morality of depleting even our private
bushland of these superb plants. Many are harvested in the wake
of forestry operations, so that even if the site is to be regenerated,
the new environment will be devoid of its original fern population.
There is a strong argument for maintaining corridors along gullies
in areas being logged, so that at least this distinctive and
irreplaceable portion of our native forests has a chance of survival.
There are a number of equally splendid alternatives to Dicksonia,
principally the various Cyathea species found widely both
in Australia and New Zealand. Most commonly grown are C. australis,
the rough tree fern, which has much the same distribution as Dicksonia
antarctica, and C. cooperi, Cooper's or the scaly
tree fern, which prefers a warmer climate, growing from northern
Queensland to southern New South Wales. These species will die
if harvested in the Dicksonia manner, and are more readily
propagated and faster-growing, and, consequently are not under
the same threat of depletion.
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Bird's nest
fern, Asplenium nidum |
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Staghorn fern, Platycerium spp. |
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Variegated Adiantum spp. |
Elkhorns and staghorns
These are epiphytic ferns, members of the genus Platycerium.
They look spectacular attached to a trunk, and create their own
micro-environment, trapping their nutrients within their leaves
from material falling from the forest canopy.
Fishbones and water ferns
The principal fern genera which answer this description is Nephrolepis,
also well-known as the sword or Boston fern, of which there a
seemingly endless number of varieties, some of which I have illustrated
here. They are generally hardy and easily-maintained and useful
both inside and out, with some varieties having very long fronds
making them particularly appropriate to basket or hanging pot
use.
The water ferns come from the genus Blechnum, and superficially
resemble Nephrolepis. These tough ferns invite more popular
use in the home garden. Of the eighteen Australian species, B.
nudum, the fishbone water fern, is the most commonly found
and cultivated. Excellent for planting en masse under larger
ferns or spreading shrubs and trees.
Maidenhair ferns
The genus Adiantum is a vast, containing over 200 species,
and many further varieties derived from them, including ten Australian
species.
Bracken
Pteridium esculentum is the wild card in the fern pack.
It, and its northern hemisphere counterpart, P. aquilinum,
have more written about their removal than their cultivation.
It defies all the normal rules for cultivation, thriving across
the country, encouraged rather than endangered by human activity.
It is toxic to sheep, cattle and horses, is a known cause of
bowel cancer in those foolish enough to eat it, and eagerly infests
neglected land disturbed by man, where it provides highly inflammable
fuel for bush and grass fires. Strong applications of glyphosate
(or more vigorous herbicides) can have some effect, along with
repeated physical removal.
Propagation by spore
Unlike the flowering plants, ferns reproduce from spores which
are carried on the fertile fronds of spore-bearing ferns, which
are known as sporophytes. These fronds are often distinctly different
from non-bearing fronds, and the minute dust-like spore are produced
in structures known as sporangia, which are usually grouped in
clusters or patterns called sori, felt-like brownish markings
on the underside of the frond. I was once asked by someone who
should have known better how to treat the plant for this affliction,
which he thought were some sort of scale insect.
Each spore develops into a structure known as a prothallus,
which bears both male and female organs, which in turn produce
the male and female reproductive cells. When conditions are damp
enough, the sperm swim to the ovum and fertilise, with the resulting
cell growing into a sporophyte, or spore-bearing fern.
The fine dust-like spore are efficiently carried great distances
by wind , which explains the vast distribution of many fern genera.
With care and great attention to maintaining ideal conditions,
it is possible for anyone to grow ferns from spore with basic
facilities and a great deal of patience. The biggest problem
faced is that the conditions ideal for germination and successful
growth are also just dandy for all manner of fungi, which will
rapidly bring the process to a halt.
Space here doesn't permit an adequate description of the technique.
However, if you're interested, you'd best be advised to get hold
of a good book on ferns or join the local branch of a fern society
to seek the advice of those who have already succeeded.
Propagation by division
The easiest way for the home gardener to generate new fern plants
is by simple division. Ferns naturally send out adventitious
shoots which in turn become the rhizomes from which new plants
will grow. When contained in a pot, these rhizomes form a solid
tangle with the roots, sending up a number of new plants, which
can be easily divided when large enough by cutting the mass with
a sharp or serrated knife and potting the newly-separated plants.
This method is appropriate for most ferns normally grown in
containers, including Nephrolepis, Adiantum, and Pteris species.
The process is continuous, and by dividing one's collection every
year or so, a huge number of plants can very easily be achieved
with the minimum of expertise.
Propagation from bulbils
Some ferns, such as Asplenium and Polystichum species,
produce new young ferns, known as bulbils, growing piggy-back
style on mature fronds. Techniques vary, but it is quite easy
to encourage these plants to grow. Containers can be placed alongside
the 'mother' fern, and the mature frond pegged down so the crown
of the new fern is kept in contact with the growing medium, to
be separated when it has taken root.
Alternatively, the entire front can be removed, held in contact
with the growing medium and allowed to die while the new plants
take root. And, most simply, especially with the common and appropriately
named hen-and-chicken fern, Asplenium bulbiferum, the
bulbil can be carefully removed from the 'mother' frond and potted
as it is.
A good starting medium is 50:50 perlite:peatmoss, with a very
small quantity of a slow-release fertiliser included, until the
plant is well established. In all cases, plenty of humidity,
such as under plastic or glass, will ensure a greater chance
of success.
Tissue culture
I observed this technique at the laboratory of Westland Nurseries
in Hobart, and it says something about the technique that they
refer to the operation as a 'laboratory' rather than a nursery.
Less than 1 cm is taken from the tip of an adventitious fern
shoot and placed in a sealed flask on a seaweed-derived agar
solution on which it multiplies many times. These tiny new tips
are skilfully divided and encouraged to take root after further
growth, to be divided yet again, before finally being potted
into trays for wholesale distribution across the country, around
fifteen months after taking cutting the tip from the stock plant.
Hygiene and temperature control are critical and not practical
for the home grower to contemplate. However, the technique does
offer great advantages for the commercial propagator over the
other methods, in terms of reliability, consistency and the vast
numbers of plants that can be generated from such small amounts
of original material.
References
Handbook of Ferns for Australia and New Zealand by
Christopher Goudey. Lothian Publishing, Melbourne, Australia.
Encyclopaedia of Ferns by David Jones. Lothian
Publishing, Melbourne, Australia. The definitive work if you're
really serious about ferns!
Ferns and Allied Plants of Victoria, Tasmania and South
Australia by Betty D. Duncan and Golda Isaac. Melbourne
University Press, 1986. Excellent taxonomical details, useful
for identfiying south eastern Australian native ferns in
the wild.
Ferns in Australia by D. L. Jones and C. J. Goudey.
Reed Books Pty. Ltd., Frenchs Forest, NSW, 1984, revised 1988.
Good for popular species.
Ferns and Fern Allies of New Zealand by Eric Heath
and R.J. Chinnock. A.H. & A.W. Reed, Wellington, NZ, 1974.
Fern Grower's Manual by Barbara Joe Hoshizaki
and Robbin C. Moran. Timber Press, Portland, Oregon, USA, 2001.
Vast!.
Key Guide to Australian Palms, Ferns and Allies by
Leonard Cronin. Reed Books Pty. Ltd., Frenchs Forest, NSW, 1989.
The Plantfinder's Guide to Garden Ferns by Martin
Rickard. Timber Press, Portland, Oregon, USA & David Charles,
Newton Abbot, Devon, UK, 2000. Excellent informed descriptions
of a comprehensive range of popular ferns. Had dinner with the
author once. |
