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New Zealand Native Plants for Use in Aquariums and Ponds

Dr John Clayton <clayton-at-hamilton.niwa.cri.nz>
National Institute of Water & Atmospheric Research (NIWA), and New Zealand Aquarium Enterprises (NZAE)

Abstract

The international search for potential new aquarium plants and the geographical isolation of New Zealand has generated overseas interest in our indigenous aquatic plant species. At the same time, a national desire to minimise use of potentially invasive exotic species in the New Zealand aquarium trade, prompted a research screening programme to identify which if any of our native species may be suitable for aquarium and pond use. This illustrated paper discusses a range of different plants, looks at their growth habit in the natural environment and considers their potential use in aquariums and ponds.

The native aquatic plants of New Zealand can be grouped in to six different life forms. The mosses and liverworts found in New Zealand are mostly cosmopolitan and are best suited to specialist tanks. Charophytes (macroalgae of the genera Chara and Nitella) are also cosmopolitan. A number of charophytes are desirable in that they provide refuge for juvenile fish, they help condition the water and can be very attractive with their distinctive growth forms and appearance. Delicate compact charophyte species can make an attractive foreground in an aquarium. Of the tall growing submersed species, New Zealand has few endemic milfoils and pondweeds and those with greatest potential are illustrated and discussed. The most interesting and diverse group of water plants are those that form turfs. New Zealand has a wide diversity of turf species with different leaf shapes and growth habits. Spread is usually by rhizomes and given good light conditions they can form a vigorous compact carpet across the base of an aquarium or pond. One internationally well known, but incorrectly named example is Lilaeopsis novae-zelandiae. The New Zealand native Isoetes can provide an ideal foreground plant in aquariums.

New Zealand has no native water lilies, while the only free-floating species are universally common. A wide variety of small to large native emergent species are found around the margin of waterbodies. Some are grown for ornamental ponds while others are used in wetlands designed to treat or purify waste water.

Issues relating to the collection, culture and marketing of aquatic plants have particular relevance to their suitability in the aquarium trade. The question of what makes a good aquarium plant is considered, including why exotic plant species are so successful and still provide the bulk of the aquarium and pond market both in New Zealand and internationally. More screening, culture trials and market evaluation is required on selected species.


A tank of native New Zealand plants, including Chara globularis, Myriophyllum propinquum, Triglochin striatum, Isoetes kirkii, Glossostigma elatinoides, Ranunculus amphitrichus, and Lilaeopsis ruthiana

Introduction

New Zealand is located over 1,600km (3 hours flying) south east of Australia. It is has a warm temperate climate, a moderate rainfall and a wealth of lakes and rivers. The most characteristic feature of New Zealand vegetation is the large proportion of endemic species (i.e. species found only in a given country). This affords a striking contrast to the flora of some continental land masses including the UK, which have few endemic species [1].

New Zealand was predominantly forested until the 1800s and of the different kinds of flowering vegetation and ferns belonging to the pre-European vegetation, around three-quarters are endemic. These include many that are prized as garden shrubs and for alpine or herbaceous gardens (e.g. evergreen veronicas - Hebe, Nikau palms - Rhopalostylis, New Zealand flax - Phormium, tussock grasses, daisy bushes - Oleraia).

With the advent of European colonisation in the late 1800s and the subsequent extensive agricultural development, large areas of land were cleared of native vegetation and over 90% of the original wetlands are now drained for farming. Associated outcomes of agricultural development include erosion due to deforestation, which combined with increased run-off of nutrients, has led to nutrient enrichment and siltation of many smaller waterbodies in particular.

Another post-European impact has been the extensive introduction of adventive plants and animals. New Zealand had no native mammals (with the exception of two flying bats) and now in addition to numerous farmed animals there are also many wild possums, rabbits, deer, goats and pigs which continue to damage and even destroy native vegetation throughout the country. By 1940 about 500 alien plant species had become established and these too have had a marked impact on the native vegetation. Apart from exotic forestry, invasive spread of uncontrolled alien species has become a major management issue. Within natural waterbodies, the influence of land management practices within catchments along with the effect of invasive exotic species has resulted in few waterbodies retaining the natural or original indigenous aquatic vegetation, apart from those still isolated from human influence.

The international search for potential new aquarium plants and the geographical isolation of New Zealand has generated overseas interest in our indigenous aquatic plant species. Fortunately, isolated and protected areas still remain, so that it has still been possible to identify and retrieve most of our original aquatic plant species. Many large clear-water lakes have been protected by their vast size, under-developed catchments and reserve status (e.g. National Parks), while small isolated lakes with limited or no public access often still retain the original aquatic vegetation.

Interest in our indigenous aquatic species and a national desire to minimise use of potentially invasive exotic species in the New Zealand aquarium trade, prompted a research screening programme to identify which if any of our native species may be suitable for aquarium and pond use. This illustrated paper discusses a range of different plants, looks at their growth habit in the natural environment and considers their potential use in aquaria and ponds.

Aquarium trials using native plants

Plants are used in aquaria to provide: A good aquarium plant should have the following attributes: Unfortunately many of the above attributes that describe a good aquarium plant can make them undesirable escapees. Some of the most serious weed problems in countries around the world can be traced back to deliberate or accidental release of aquarium plants into natural waterbodies.

Research to identify the potential suitability of New Zealand native aquatic plants for use in aquaria began with the view of providing safe alternatives to a range of species regarded as undesirable or of significant weed potential. Legislation in New Zealand prohibits the sale and distribution of a certain aquarium and pond plant species (e.g. elodea densa [i.e. Egeria densa], elodea crispa [Lagarosiphon major], hornwort [Ceratophyllum demersum], water hyacinth and salvinia). Furthermore, there are restrictions on the importation of a range of aquarium and pond plants, while others that are not specified as approved or prohibited species can only be imported after a permit has been granted, followed by certification verifying disease and pest free growth while under quarantine, plus an acceptable "risk assessment" evaluation carried out at the importer's expense.


Lagarosiphon major and Egeria densa - not New Zealand natives, but they grow with such robust growth forms they are exported.

Approach

Thirty native species were initially screened. Emphasis was given to choosing submersed plants or semi-aquatic turf forming species that would be compatible for use in aquaria. Plants were grown in 80 litre aquaria within a climate control room under a range of temperatures, lighting and sediment types. Sediment trials used river sand, fine volcanic gravel and 'fruit salad' aquarium gravel. Light experiments used Gro-lux, cool white and True-lite fluorescent tubes as well as incandescent bulbs. A 14 hour photoperiod was selected and light levels were adjusted to give similar intensity. Temperatures examined included 15, 20, 24, and 28C (59, 68, 75 & 82F). The growth and appearance of the plants was closely monitored over the period of the trials with particular note taken of their establishment success, growth habit and aesthetic appeal.

Results

No significant differences could be attributed to the sediment types that were tested. Aquatic plants are opportunistic with respect to nutrient uptake and they are able to extract their nutrient requirements from either sediments or water, depending on which source is most readily available. Similarly, no significant differences in plant performance were found which were attributable to lighting differences. Sufficient light was available for healthy plant growth from all four light sources. Temperature proved to be an important factor for plant performance. Only a limited number of the species tested were able to tolerate temperatures as high as 28C (82F), while many of the species tested were able to tolerate 24C (75F) and lower. This is an important consideration, since some tropical tanks, particularly those with spawning tropical fish, are raised to temperatures around 28C.

Native aquatic plants

Rather than discuss in isolation each of the species that were tested, the following grouping of native plants, within life forms, will help provide an overall perception of what type of plants they are. Not all of the life forms discussed include endemic species (i.e. specific to country in question), since some are native with representatives found in Australia or elsewhere; alternatively they may be cosmopolitan with an international distribution.

Bryophytes

The mosses and liverworts found in New Zealand are mostly cosmopolitan [2]. Mosses and liverworts are typically found in damp shaded places such as beneath forests, along rocky river and lake margins and they can dominate forested waterbodies. A recent discovery in the South Island of New Zealand was the presence of mixed mosses and liverworts within clear water glacial lakes growing down to the remarkable depth of 70 metres. Although difficult to identify, cultures grown in humid atmospheric conditions suggests these deep water life forms are simply modified growth forms of terrestrial species. Bryophytes grow very slowly, tolerate low light conditions and are best suited to specialist low light tanks where they are allowed to dominate without disturbance. Mosses in particular are very fragile and are only suitable for small fish. Bryophytes tend to be collected from wild sources, since although they can adjust to tank environments, they tend to grow best and are often only available in any quantity when found in flowing water. Unfortunately, many collectors have been known to supply mosses (under the common name of Java Moss) which are not truly aquatic, with the inevitable result that little or no growth is possible within aquariums [3].

Of the few native moss species tested, only Hypnodendron marginatum grew well under all test conditions. Many other mosses occur in New Zealand and one endangered species (Fissidens berteroi) is undergoing further study with a view to identifying its ecological requirements to ensure future protection or culture. There are many moss genera around the world and the genus Fissidens alone has over 900 species alone, but like many other genera, only a few species are truly aquatic. Aquatic moss species are often poorly documented and further study will be required on this diverse group of plants. There is little advantage in considering any of the New Zealand species further at this stage when there are already well established tropical mosses (e.g. Java Moss or Vesicularia dubyana which prefers temperatures exceeding 23C or 73F) and cold water mosses (e.g. Fontinalis antipyretica up to 20C or 68F maximum) available for aquarists. Furthermore there are many other cosmopolitan mosses (eg. species of Drepanocladus, Amblystegium and Fontinalis as well as other genera) which have aquatic forms and can be grown successfully in aquaria.

Compared to the mosses there are very few truly aquatic liverworts. Of the deep water New Zealand specimens, none are likely to be suitable on account of their very slow growth rate. There are only two well known and cosmopolitan liverworts grown as free floating tank covers. Riccia fluitans (commonly called Crystalwort) is a popular aquarium plant, while the other liverwort Ricciocarpus natans is seldom used. Both species are native to New Zealand.

Charophytes

Charophytes are macroalgae of the genera Chara and Nitella. They are commonly referred to as Stoneworts and are often associated with hard or alkaline waters where deposits of calcium on to the plant surfaces has resulted in their common name. Most New Zealand waters are slightly acid to neutral (pH 6-7) so calcium deposits are rarely seen on charophytes in this country. In their natural environment charophytes form meadows across the bed of lakes down to 40 metres in clear water. Charophytes are desirable in both natural waterbodies and in ponds or aquaria in that they provide refuge for juvenile fish, harbour an abundant assortment of small fauna and they help condition the water.

Many books on aquarium plants fail to even mention this attractive group of plants, while those that do often include only one or two species of Nitella. Undoubtedly one of the reasons is that some species are too delicate for general purpose use in tanks while others may be readily eaten or disturbed by a variety fish. Nevertheless, some species can form excellent robust growths and Nitella flexilis, which can tolerate temperatures up to 28C is most commonly sited [4]. Species with an open branching growth habit can be suitable for juvenile fish, while delicate compact species can make an attractive foreground in a tank.

Nearly all species in New Zealand are cosmopolitan. Four species of Chara and six species of Nitella are commonly found natives in New Zealand, although only Nitella hookerii is endemic. N. hookerii is a fast growing, fine, highly branched plant which is easy to propagate. It may occasionally require control in some waterbodies, including in aquaria and tanks. These properties can make this plant ideal for spawning fish and as a refuge for small fish. Perhaps the most attractive of the native Nitella species investigated, include N. leptostachys, N. pseudoflabellata and N. hyalina. These are slower growing and more compact in growth habit. Three Chara species which are particularly attractive are Chara fibrosa, C. corallina and C. globularis. The first two species are unreliable and too difficult to grow in aquaria, but they can be grown in outdoor ponds successfully. C. globularis on the other hand is relatively hardy, can tolerate higher temperatures (up to 24C) than the other charophytes and with its attractive emerald green colour, it makes an attractive backdrop to an aquarium. The growth of charophytes in warm water aquariums generally deteriorated when temperatures exceeded 20C. Most of the charophytes can be propagated from vegetative material, however, the potential to grow Chara vulgaris (a species that is widespread in many countries but is not present in New Zealand) and Nitella pseudoflabellata (a New Zealand native) from seed (oospores) requires further investigation as this may well overcome some of the difficulties in collecting, transporting and establishing easily damaged specimens. Unfortunately most of these species appear to be better suited to cold water aquariums and outdoor ponds, provided they are not exposed to feeding pressure or damage by larger fish such as goldfish.


Charophyte meadow comprised of mixed species of Chara and Nitella.

Chara corallina, showing orange reproductive organs.

Tall-growing submersed vascular species

Pondweeds and milfoils are the main plants in this group. There are around 100 species of pondweed worldwide [5], but their suitability for use in aquariums requires further research. Potamogeton species from the temperate zone are claimed to be unsuitable for use in aquaria [6] since they are prone to dropping their leaves. Meanwhile, Potamogeton gayi (a fine leaved, South American species) has proven suitable for use in tropical aquaria, while a number of other species (e.g. P. perfoliatus, a broad-leaved species) appear better suited to cold water aquaria or to outdoor ponds. Unfortunately New Zealand has few endemic species [7]. Pondweeds and milfoils are widespread around New Zealand and they grow in clear or turbid water, often reaching to the water surface from depths down to 3 metres. Potamogeton ochreatus (blunt pondweed), P. pectinatus (fennel-leaved pondweed), P. cheesemanii (red pondweed), P. suboblongus (mud pondweed) and P. crispus (curly pondweed) are the only pondweeds growing naturally in New Zealand. P. crispus is a naturalised pondweed which is already an established plant in the aquarium trade. All of the other pondweeds are native (with most also found in Australia), while P. suboblongus is the only one that is endemic. P. suboblongus has surface floating leaves but its distribution amongst alpine bogs would indicate this species is only likely to grow in cool water outdoor ponds. Its similarity in appearance to P. natans, a more hardy species already established within the aquarium trade, would suggest no further study is warranted on this species. P. pectinatus and P. cheesemanii may be useful in outdoor ponds, but they are not suited to aquaria as they appear intolerant of warm water. Potamogeton ochreatus (blunt pondweed) clearly has the greatest potential as an aquarium plant as it has entirely submerged leaves and it appears to tolerate water temperatures up to 24C. This species has long (6-10cm), parallel sided (3-5mm wide) pale green leaves (bronze in high light) and the plant is readily propagated from stem or rhizome cuttings. In appearance it is similar to P. gayi which is a popular and well established aquarium species.

Milfoils are mostly cosmopolitan, with around 40 species. Many of the milfoils originate from temperate climates in the Southern Hemisphere and USA and their low tolerance to warm water aquaria can result in poor growth and loss of submerged leaves. Some of these species may well be suitable for aquaria and ponds, but interest in obtaining new milfoil species has been reported as somewhat limited since most species tend to look alike [8]. Milfoils that have become established in the aquarium trade include Myriophyllum hippuroides and M. verticillatum, both of which tolerate water temperatures up to 23C, while outdoor ponds are generally considered a more suitable option for milfoils such as M. aquaticum (i.e. parrot's feather which may still be referred to by its old name M. brasiliense) that tend to quickly form emergent foliage under cultivation.

Of the New Zealand native milfoils , only two are endemic (M. robustum and M. triphyllum). M. robustum is an uncommon species and is classified as vulnerable in terms of its future survival [7]. It is bronze coloured and can be cultivated to produce large submersed and robust emergent leaves. Unfortunately it is rather similar to M. aquaticum (parrot's feather) in appearance and its preference for acid or peat bog habitats is likely to limit its usefulness for future commercial cultivation and also exclude its use in alkaline water or concrete lined pools. M. triphyllum (previously thought to be the same as M. elatinoides) is too difficult to cultivate and performs poorly in aquaria. M. propinquum, a native species which is also found in Australia, may be suitable for tropical aquaria (upper temperature tolerance appears to be around 23C and it is already a popular plant for use in ornamental outdoor ponds in New Zealand. This plant can be grown hydroponically since it is heterophyllous and the small aerial leaves quickly revert to an underwater growth form on submergence in ponds or aquaria. Alternatively the plants can continue to grow as prostrate mats on damp pool margins.

Other plants that belong to this life form include species of Ruppia (horse's mane weed), Zannichellia and Lepilaena. These genera are found around the world, but all have fine hair-like leaves and none have become recognised as worthwhile aquarium specimens [8]. Species of these genera that are endemic to New Zealand have no distinguishing characteristics that would recommend them for further investigation.


Myriophyllum triphyllum (left), and M. propinquum (right) with heterophyllous leaf forms (smaller emergent leaves at tips, and larger feathery submersed leaves).

Myriophyllum triphyllum in the foreground - the taller background plant is Potamogeton cheesmanii.

Low-growing, turf species

This is a most interesting and diverse group of water plants. New Zealand has a wide diversity of native and endemic turf forming species which have different leaf shapes and growth habits. Spread is usually by rhizomes and given good light conditions they can form a vigorous compact carpet across the base of an aquarium or pond. This group of plants can be divided into those with filamentous or grass-like leaves and those with broad leaves:

Grass-like species

Lilaeopsis novae-zelandiae, a reasonably well known example of this group, has the unfortunate distinction of being wrongly named (probably L. brasiliensis) and incorrectly identified as of New Zealand origin (probably South American). In fact this rather pretty and readily cultivated plant is not even present in New Zealand. The 'true' Lilaeopsis novae-zelandiae is a New Zealand coastal plant associated with brackish habitats [9]. Although specimens of this plant have not been specifically tested for suitability in aquaria, it is almost indistinguishable from inland populations of Lilaeopsis ruthiana and taxonomical distinction between these two species may not be justified. Lilaeopsis ruthiana tends to have more cylindrical tapering leaves and has been cultivated successfully during the experimental screening trials in water temperatures up to 28C. Another plant with good aquarium potential is the native Triglochin striatum (arrow-grass). This attractive bright green reed like plant was cultured successfully in all growth trials and it also tolerated temperatures up to 28C.

The largest and most distinguished member of this group is Isoetes (Quillwort), which can form a compact turf to 6 metres in clear water lakes in New Zealand. This is an ideal midground plant in aquariums, but no runners are produced so plants must be individually planted. Isoetes lacustris and the larger I. malinverniana are often noted in aquarium literature, but there often appears to be a shortage of supply on account of the continuing decline in their natural occurrence, and from difficulties experienced with the culture of these plants. Although propagation by spores has been suggested [8], it has also been recommended "that one should be satisfied with collecting these plants under natural conditions and letting them stand without multiplying in aquaria" [10]. The Isoetes species noted in the aquarium literature are reported to have a limited temperature tolerance with culture recommended to be between 18-22C. Trials with the New Zealand Isoetes suggest a greater temperature tolerance with successful culture in cold water (10C) and warm water up to 24C. There appears to be three varieties of one genus (I. kirkii) in New Zealand [2] and further study of their taxonomy and potential use in aquaria is recommended. One growth form collected from a southern lake grows very tall blades up to 0.5-1m long (similar in appearance to I. malinverniana). This growth habit continues even in aquaria, with the result that leaves grow across the surface. The more common shorter variety (10-30cm) can be collected from the many abundant natural sources and grown under appropriate culture conditions so as to produce robust specimens with up to 40 leaves, before being transplanted into aquaria. There is considerable potential for large scale culture of this species to form large many-leaved plants, either from spore material or by using the typically small statured plants from natural field populations.


Isoetes kirkii, cultured.

Isoetes kirkii, wave-washed, shallow water wild plant.


Isoetes kirkii in its natural habitat forming compact, low-growing turfs.

Lilaeopsis ruthiana, a New Zealand native which forms a compact turf.

Broad-leaved species

This diverse group of plants requires further study, but initial investigations indicate that a number of potentially useful species exist. There are two prostrate, creeping, mat forming Glossostigma species, which is one genus rarely mentioned in aquarium texts. G. diandrum was the easiest of the two species to establish, forming bright green foliage and a compact mat across the base of tanks in either cool water or in warm temperatures up to 24C. G. elatinoides has broader leaves, but is less tolerant of warm water. Both species require good light for effective growth. A similar plant is Elatine, a cosmopolitan genus, with only one New Zealand species (Elatine gratioloides or waterwort), but this appears to have no advantage over E. macropoda, a European/African species already established in the aquarium trade. One well known aquarium plant allegedly of New Zealand origin is Crassula helmsii. This plant has become naturalised in other countries and can even be problematic in outdoor ponds in the UK, where its growth greatly exceeds the vigour ever experienced in the limited number of coastal sites of the South Island of New Zealand. This could yet be another example of incorrect identification (as for Lilaeopsis novae-zealaniae) as there are around 1500 species of Crassula, many of which are cosmoplitan. Further study is recommended of the many other endemic species in this genus.

A particularly interesting native buttercup (also found in Australia) is the non-weedy Ranunculus amphitrichus (waoriki). This plant has palmate, non-hairy leaves, can be readily grown as an emergent plant but will adapt to submergence within an aquarium even in warm water up to 24C. Worldwide there are approximately 35 species of Ranunculus that are aquatic and other potentially useful aquarium species are likely to exist, but of the New Zealand species R. amphitrichus appears to have the greatest potential and the most suitable growth characteristics.

There are many other New Zealand species of this low growing turf forming nature, but unfortunately there is often little if any notable difference in appearance to their counterparts from other countries and their use as aquarium plants is probably not worth investigating further. For example, Eleocharis pusilla looks like E. acicularis (hair grass), but it is less robust and is unable to grow in warm water conditions. Pilularia novae-zelandiae (Pillwort) is an uncommon and unusual fern with distinctive concentric coiling of its terminal, hair-like fronds, but it is largely indistinguishable form the popular and readily cultivated P. glogulifera. There are also a number of endemic and native Hydrocotyle species (Pennyworts) in New Zealand that have never been tested for their suitability in aquaria, however the presence of the well established, cold and warm water tolerant H. vulgaris (Pennywort or Umbrella plant) within the aquarium trade, reduces the value in exploring this group any further.

Free-floating and rooted floating-leaved plants

New Zealand has no native water lilies. The only native rooted submersed plant with floating leaves (Potamogeton cheesemanii) has already been discussed above, while the only free-floating species are cosmopolitan and include Ricciocarpus, Lemna and Spirodela (duckweed), Azolla (water fern) and Wollfia (water meal).


Azolla rubra, a dark red New Zealand native water fern. Forms a floating mat.

Emergent marginal species

The emphasis of this paper has been on aquarium plants, with a note made of those that are also suitable for outdoor ponds. Pond plants that are only suitable for marginal areas of outdoor ponds and have no potential for use in aquaria, will not be discussed in this paper in any detail.

A wide variety of small to large native and endemic emergent species are found around the margin of waterbodies or grow within the waters edge. Species of Schoenoplectus, Eleocharis, Baumea, Cyperus, Typha and Juncus are common. Many of the genera in this group are cosmopolitan and are well known by pond plant growers and nursery suppliers. Some species are cultivated specifically for ornamental ponds while others have been used in wetlands designed to treat or purify waste water.

Plant culture and supply

Following the native plant screening trials a number of the most promising native species were evaluated for their market potential. Information was sought on their suitability for collection from natural sources, their ease of propagation, their durability with respect to handling, packaging, transport and replanting, and the degree of public interest when stocked in shops. Display tanks were exhibited at various functions and conferences at different locations and pamphlets were made available with information on "New Zealand Native Species - Description of alternative species" [11].

A number of issues were identified during the study of potential native aquarium species for the New Zealand market:

Legislation
New Zealand has legislation that protects many waterbodies (e.g. Reserves, Conservation Orders and National Parks) and this limits the areas that can be harvested. Furthermore, the collection of any native species, if not prevented by the Plants Act (i.e. species nominated for protection), would require a permit or consent which would only be granted following an appropriate environmental assessment that demonstrated native plant removal could be carried on a sustainable basis with minimal detrimental impact on the environment.
Collection
The quality of native plants collected from natural sources may be inadequate, of inconsistent quality or too seasonal for this option to be feasible. Competition from other plants, pest damage and climatic stresses can limit their suitability for reliable supply. Many New Zealand waterbodies have been severely impacted by invasive species from other countries and this has limited native plant resources through competitive displacement, particularly over the last 50 years.
Handling
Many aquatic plants, particularly those grown in aquaria, are rather delicate. Removal from one environment and transplanting to another can prove detrimental to plant health and appearance. Removal of damaged leaves and pruning of shoot tips may be necessary to enable specimens to recover and adjust their growth to any new environment.
Economics
Growers and sellers have little interest in culturing or stocking new plants if the public are not aware and interested enough to create sufficient demand for the product. Demand arising from public interest must inevitably be a function of population and in this respect New Zealand with only 3.5M people represents a small market. There is also a matter of economy of scale where collection of limited quantities of diverse species from different locations is not profitable, compared to larger scale collection of a limited variety of plants (e.g. Oxygen weed) often from a single source. Interest in aquarium plants, particularly unusual or uncommon varieties, also appears to be a cultural matter, where some countries are renown for their greater interest in tropical fish rather than plants, while for others the balance may even reverse.
In order to resolve some of the obstacles noted above it may be beneficial to consider the potential of New Zealand native plants to supply a substantially larger international market. The first consideration is whether any of these species can be effectively and economically cultured hydroponically within any of the existing large scale commercial culture facilities. The advantage of this option is that only a limited initial supply of stock plant material is required, so that continuing freight costs are avoided and plant quality can be controlled. The economics of this option may also be preferable when natural resources can be limited, demand is irregular and too limited to cover collection costs, or when quality from wild sources is unreliable. Collection of native species from natural resources should only be considered as an option when there is a temporary shortage of supply from cultured sources to meet market demand and provided there is an acceptable minimum impact which ensures the sustainability of the resource is not threatened.

Commercial culture within New Zealand may also be an option, particularly if the additional international demand is sufficient to justify their culture so that promotion of these species on to the local market becomes economical. New Zealand culture also has the advantage that all of the native species discussed are temperate plants which are well suited to New Zealand climatic conditions, as well as the renowned favourable growing conditions in this country which are conducive to excellent plant growth. Interest from European countries in potential culture of aquarium plants in New Zealand for international supply has arisen, since significant savings in plant culture may be achieved through savings in the reduced need for supplementary heating and lighting.

Alternative approaches should also be considered. For example, the potential large scale culture of Isoetes from spores should be investigated further, while the option of nuturing wild sourced plants by providing specialised culture conditions prior to marketing, may well be economically preferable. Species that can be grown hydroponically out of water probably provide the best potential for commercial culture, while true aquatics that can only be grown under water are often slower to grow and more demanding of space. Such plants may well be better sourced from natural populations, provided there are adequate and sustainable sources.

Finally, one interesting question still to consider is why exotic plant species are so successful and still provide the bulk of the aquarium and pond market both in New Zealand and internationally. Inevitably, the bulk of the aquarium trade is based primarily on tropical and sub-tropical fish species which are well renowned for their diversity of size, colour and form. This has a direct bearing on the type of plants which are best suited to growth in these conditions. Aquatic plants of tropical origin are naturally suited to tropical aquaria, while the range of temperate aquatic species able to tolerate tropical aquaria is somewhat restricted. Insufficient research or knowledge on potential alternative plants, popular aquarium books based largely on tropical species and the proven ease of culture and performance of the existing range of commercially available species, have all contributed to the market domination by existing species.

Cold water aquaria and outdoor ponds tend to be based on different fish and often include alternative plant species. In this regard it is interesting to note that some sub-tropical water plant species have been highly successful in their global distribution and vigorous growth even in temperate climates. For example, various species of Oxygen Weed (such as elodea densa [Egeria densa] and hornwort [Ceratophyllum demersum])) have recently come to dominate many New Zealand waterways. Their abundant and healthy growth have proven ideal for use in cold water aquaria and outdoor ponds both in New Zealand and in other countries. In fact it was from initially imported plants used within this sector of the trade that led to many of the current populations which have developed from escaped or deliberately released plants entering in to natural waterbodies. Their hardy nature, resistance to fish browsing, ease of propagation and adaptability to indoor aquaria or outdoor ponds have been largely responsible for their adoption by commercial plant suppliers for cold water aquaria and the pond plant trade. Ironically, New Zealand has now become a significant supplier of these same exotic species on to the international market. Their abundance and exceptional quality from natural populations avoids costs associated with their culture and at the same time New Zealand can meet any shortage of supply within the Northern Hemisphere when their spring demand escalates.

More screening, culture trials and market evaluation is recommended on those New Zealand native species discussed in this paper. The challenge beyond this is to identify those species that have qualities comparable to or even better than those species already established within the aquarium trade and then to develop their market potential accordingly.


Scuba diver collecting oxygen weed for NZ market and export.

The author making a hole in the ice of a South Island alpine lake so he can go for a dive.
 
Pupu Springs (shown in two separate photos, 1 and 2) claimed to have the "clearest water in the world" (they've even done studies). A variety of plants, including milfoils, watercress.

References

  1. Enclycopaedia Britannica. William Benton Publisher, 1965, Volume 16.
  2. Coffey, B.T., and Clayton, J.S. New Zealand Waterplants. Ruakura Agricultural Centre, Hamilton. 1988, pp 63.
  3. James, B. A fishkeeper's guide to Aquarium Plants. Salamander Books Ltd, London. 1986, pp 117.
  4. Stodola, J., Holga Windelov's Tropica Color Catalogue on Aquarium Plants: A Complete Introduction. T.F.H. Publications 1987, pp 128.
  5. Cooke, C.D.K. Water plants of the World. Dr W. Junk b.v., The Hague. 1974, pp 561.
  6. Rataj, K., and Horeman, T.J., Aquarium Plants: their identification, cultivation and ecology. T.F.H. Publications 1977, pp 448.
  7. Johnson, P., and Brooke, P. Wetland Plants in New Zealand. DSIR Publishing, Wellington, 1989, pp 319.
  8. Muhlberg, H. The Complete Guide to Water Plants. EP Publishing Ltd, German Democratic Republic 1982, pp 391.
  9. Affolter, J.M. ``A Monograph of the Genus Lilaeopsis (Umbelliferae)''. Systematic Botany Monographs 1985, 6: 103-118.
  10. Roe, C., A Manual of Aquarium Plants. Shirley Aquatics Ltd, Shirley, UK, 1967, pp 111.
  11. Clayton, J.S. ``Culture Water Plants: New Zealand Native Species - Description of Alternative Plants''. Aglink HPP 186, Media Services MAF, Wellington, 1982. pp 4.
importation and original HTML translation c/o Len Trigg
Up to Plants! <- Plants <- The Krib This page was last updated 29 October 1998