''Urtica ferox'', commonly known as tree nettle and in
Māori
Māori or Maori can refer to:
Relating to the Māori people
* Māori people of New Zealand, or members of that group
* Māori language, the language of the Māori people of New Zealand
* Māori culture
* Cook Islanders, the Māori people of the C ...
: ongaonga, taraonga, taraongaonga, оr okaoka, is a species of nettle
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to New Zealand. Unlike the other species in the genus ''
Urtica
''Urtica'' is a genus of flowering plants in the family Urticaceae. Many species have stinging hairs and may be called nettles or stinging nettles, although the latter name applies particularly to ''Urtica dioica''.
''Urtica'' species are food f ...
'' found in New Zealand, all of which are herbaceous, ongaonga is a large woody shrub that can grow to a height of , with the base of the stem reaching in thickness. It has large spines that can result in a painful sting that lasts several days.
Ongaonga is the main source of food for larvae of the
New Zealand red admiral
The New Zealand red admiral (''Vanessa gonerilla'') is a butterfly endemic to New Zealand. Its Māori name is ''kahukura,'' which means "red cloak". The red admiral is a member of the family Nymphalidae, the subfamily Nymphalinae and the tribe ...
butterfly or kahukura, ''Vanessa gonerilla''.
Description
''U. ferox'' can grow to a height of 3 m (9.8 ft) with the base of the stem reaching 12 cm (4.7 in) in thickness. The pale green leaves are very thin like a membrane and the surface of the leaf, stems and stalks are covered in stiff stinging hairs that can grow up to long. These spines are prominent along the salient mid-vein and leaf margin. The leaves range from in width and in length, these are oppositely arranged and there are two stipules per node. The leaf shape is ovulate-triangulate with a serrated leaf margin each bearing a spine of up to . The spines covering the leaf surface, stem and stalk are generally no larger than in length, the spines on the older darker bark are smaller and softer - these don't cause a sting. This nettle is winter deciduous in cold climates, evergreen in mild climates and can lose its leaves in drought conditions if it is growing in shallow soils.
Flowering occurs from November to March and because ''U. ferox'' is a
dioecious
Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...
shrub it will
cross pollinate
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...
, with transferral between the flowers enabled by the wind. Pollen grains are collected by the densely packed
stigmas on the flowers and seed dispersal is carried out by rolling, wind, and by birds. The fruit, which are
achene
An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...
s, mature in January, each containing one 1.5 mm long, brown coloured, ovoid-shaped seed which takes one month to germinate. In his study on the germination behaviour of 5 different vascular seeding species, C. J. Burrows found that ''U. ferox'' had the lowest germination rate of 59% compared to >85% for the other similar species. He surmised that it is capable of building up a large
seed bank
A seed bank (also seed banks or seeds bank) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease res ...
in the soil which may survive for several years, citing that European species in the genus
Urtica
''Urtica'' is a genus of flowering plants in the family Urticaceae. Many species have stinging hairs and may be called nettles or stinging nettles, although the latter name applies particularly to ''Urtica dioica''.
''Urtica'' species are food f ...
produce seed banks.
Toxin
The toxin present in the spines is
triffydin (or tryfydin). This toxin contains
histamine
Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discovered in ...
,
serotonin
Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...
and
acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
, the latter causing powerful stimulation of the parasympathetic nerve system. Multiple stingings can have a very painful reaction which causes inflammation, a rash, and itching. In high concentrations it can also cause: loss of motor movement, paralysis, drop in blood pressure, convulsions, blurred vision, confusion and in extreme cases, death.
Acute
polyneuropathy can occur due to ''U. ferox'' stings; and there has been one recorded human death from contact—a lightly clad hunter who died five hours after walking through a dense patch.
[''Poisonous native plants''](_blank)
Te Ara: The Encyclopedia of New Zealand There is also one other likely death, with the mystery of the death only being solved by the pathologist years afterwards.
Distribution and habitat
''U. ferox'' is endemic to
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
and inhabits coastal and lowland forests and shrublands in the North, South, and Stewart Islands.
It is commonly found in clearings or forest margins, often forming large patches, from 0–600 m above sea level.
It has also been recorded on the
Hen and Chicken Islands
The Hen and Chicken Islands (usually known collectively as the ''Hen and Chickens'') lie to the east of the North Auckland Peninsula off the coast of northern New Zealand. They lie east of Bream Head and south-east of Whangarei with a total ...
along stream-beds.
Ecology
Although ''U. ferox'' is a toxic shrub, it also plays a significant part in the
phenology
Phenology is the study of periodic events in biological life cycles and how these are influenced by seasonality, seasonal and interannual variations in climate, as well as environmental factor, habitat factors (such as elevation).
Examples includ ...
of a native butterfly, namely the
red admiral (''Vanessa gonerilla''). The leaves of the tree nettle is the preferred food and provide protection for the butterfly larvae. When the larvae arrives in the leaves, it will curve the tip of nettle leaf, use the silken threads to make the leaves stick together, and construct a secure place where it can eat the food.
[Barron, M.C.,Wratten, S.D. & Barlow, N.D.(2004) "Phenology and parasitism of the red admiral butterfly Brassaris gonerilla (Lepidoptera: Nymphalidae)." ''New Zealand Journal of Ecology, 28/(1), 105-111''] Due to the caterpillar's activities, the leaves of shrub can fall off. The eggs of butterflies, also including the
yellow admiral
The yellow admiral or Australian admiral (''Vanessa itea'') is a butterfly native to Australia, New Zealand, Lord Howe Island, and Norfolk Islands. The Māori name is , which means "yellow cloak". The yellow admiral is a member of the fami ...
(''Vanessa itea''), are laid on the leaves of nettle during the spring and summer. It takes eight to ten days for the eggs to incubate. Beside these butterflies, some mammalian pests also eat the leaves of tree nettle, like the
Common brushtail possum
The common brushtail possum (''Trichosurus vulpecula'', from the Greek for "furry tailed" and the Latin for "little fox", previously in the genus ''Phalangista'') is a nocturnal, semiarboreal marsupial of the family Phalangeridae, native to Austr ...
, goats and deer. However, because no non-flying, non-marine mammals existed in New Zealand prior to human arrival in the last one thousand years, it is unadapted for them.
''U. ferox'' requires high nutrient levels found in cycling forest systems such as those found in native New Zealand forest. In these environments an “A type”
soil horizon
A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...
of rich leaf litter and humus between 10 – 80 cm is common. This is significant as the species doesn't directly compete with other flora, this is achieved through inhabiting the boundary zones between strata, therefore the high soil fertility.
Like other species in the nettle family it grows well in soils with high nutrient levels; especially in high quantities of nitrogen. Access to open sunlight and rainwater results in a rapidly growing plant able to take advantage of natural tree fall and other natural events such as land slides and flooding which clear dominating old growth species.
Cultural uses
In
Māori
Māori or Maori can refer to:
Relating to the Māori people
* Māori people of New Zealand, or members of that group
* Māori language, the language of the Māori people of New Zealand
* Māori culture
* Cook Islanders, the Māori people of the C ...
folklore
Folklore is shared by a particular group of people; it encompasses the traditions common to that culture, subculture or group. This includes oral traditions such as tales, legends, proverbs and jokes. They include material culture, ranging ...
,
Kupe
Kupe ( ~1180-1320) was a legendary Polynesian explorer, navigator and great rangatira of Hawaiki, who is said to have been the first human to discover New Zealand. Whether Kupe existed historically is likely but difficult to confirm. He is g ...
was said to have placed several obstacles to hinder pursuers whose wives he had stolen, one of which was the ongaonga.
Tree nettle has been eaten, and used medicinally. Māori used the bark of tree nettle and the leaves of
kawakawa, boiled together, to make a liquid that can be used internally and externally for eczema and venereal disease.
Also, the leaves of tree nettle play a significant part in the treating of pains. The decoction of leaves and young twigs dipped in boiled water is said to have been used for stomach ache and as treatment for gonorrhea. ''Urtica ferox'' was also a food source for Māori. The inner stems were sometimes consumed after the leaves and outer bark had been removed, the thin film that makes up the inner bark was also eaten raw and is said to have a sweet taste, it is also documented that stems were cooked after having the leaves removed.
[Best, E. (1903). "''Food products of Tuhoeland: being notes on the food-supplies of a non-agricultural tribe of the natives of New Zealand; together with some account of various customs, superstitions etc. pertaining to foods''." Wellington, New Zealand: Transactions of the New Zealand Institute.]
See also
*
List of poisonous plants
Plants that produce toxins are referred to as poisonous plants. Plants that cause irritation on contact are also described as "poisonous".
The toxins in poisonous plants affect herbivores, and deter them from consuming the plants. Plants cannot ...
References
Further reading
*
*
*
{{Taxonbar, from=Q2024246
Trees of New Zealand
ferox
Endemic flora of New Zealand
Dioecious plants