Urtica ferox – Stinging nettle

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    Ongaonga Urtica ferox or Native Stinging Nettle

    Family: Urticaceae – Nettles

    The family Urticaceae contains many plants with stinging hairs; species of Urtica, stinging nettles, are well known in NZ… and causes very persistent stings. There are four native species of Urtica and three naturalised species here. All have stinging hairs of different sizes, or distributed over the plants in different ways, or in different quantities. The most important species is U. ferox, the tree nettle or ongaonga.

    ’?Ferox’ means fierce, referring to the stinging hairs.


    Ongaonga is found throughout the North Island and west of the Southern Alps, up to a height of 600 metres above sea level. It is found in scrubland and along forest margins, where it often forms thickets. The tree’s pale green leaves are thin and membranous, ovate-triangular in shape with a truncate or semicordate base; they are pointed at the tips, with serrate margins, and rows of stinging hairs. The marginal teeth are up to 1cm long.

    Maori healing and herbal:

    Ongaonga was one of the first coverings of Papatuanuku (Earth Mother) who was separated by Tane and his brothers from Rangi, the Sky Father. It was also one of several plants that hindered the progress of Kupe and his companion Ngahue when they explored the hills and dales of NZ for the first time.

    The name ‘ongaonga’ is also given to the sandfly, to the houhere tree because its jagged-edge leaves resemble those of the nettle, to a dog’s tooth pattern in wood carving, and to a seaweed, a sea nettle, which like Medusa, stings if touched.

    The Maori treat stings by bruising and applying the leaves of either the kawakawa tree or the common dock (paewhenua, Rumex obtusifolius etc).


    The Tree nettle or Ongaonga is a small tree, soft-wooded, or shrub, growing up to three metres high, with a trunk about 12cm diameter. It has many branches – with the branches tending to be intertwined.

    Leaves are 8-12cm long, by 3-5cm wide. The leaves, branches and branchlets all have stout stinging hairs which are silicified – the head breaks off on contact, and the poison is injected into the puncture.


    These arise from the leaf axils, on spikes up to 8cm long, the sexes appearing on separate trees. There are male and female flowers. Like other parts of the tree, the flower spikes bear stinging hairs.

    Flowering is from late spring to early autumn.

    Ongaonga’s seed is ovoid, about 1.5mm long and brown-coloured.


    Tree Nettle is dangerous to livestock and man. The brittle-pointed stinging hairs cause intense pain and both man and animals may even die. Horses and dogs are the only known affected animals, and horses have been known to die quite soon after blundering into tree nettles (Aston 1909, 1934). Some losses in both horses and dogs still occur.

    Fatal poisoning in man was first recorded in 1961 when a young man died from the effect of tree nettle stinging. The facts are important enough to warrant a detailed account. Two lightly-clad men, 18 and 21 years old, went shooting in hill country of the Ruahine Ranges in the late afternoon of 26 December. On their return in the early evening they hurried through what one described as "a lot of stinging nettle and it felt like a series of needle pricks".

    Not long after, perhaps less than an hour, one of them complained of stomach ache and appeared to be exhausted. Partial paralysis set in when he lay down to rest; he had difficulty in breathing and a short time later he could not see. He was rescued, but died five hours later after being admitted to hospital. His companion suffered similarly, though not to the same extent, and did not die.?

    Three Home Guard horses died from stings in the Hutt Valley in 1944.

    Of the remaining species occurring in NZ none is held responsible for any serious damage to man or livestock. True, the naturalised U. urens, nettle and U. dioica, perennial nettle, cause short-lived irritation, intense at times, to those who come in contact with them, as does the native U. aspera, which is densely clothed with stinging hairs.

    Clinical Signs: Animals – intense pain followed by convulsions and death in severe cases. In the dog a loss of ability to scent has been reported. People – irritation an burning sensation, numbness, and in some cases some muscular incoordination. In severe cases, exhaustion, difficulty in breathing, numbness of limbs, paralysis and even death.

    Connor’s book also lists the toxins found in nettles.

    The dwarf bush nettle, U. incise, is a small herb, about 45cm high, found in lowland and montane forests, along forest margins and in shaded open places throughout the country. Leaves, up to 4cm long, are on petioles up to 7cm long, and bear occasional stinging hairs. Flowers occur from September to February.

    My main sources were ‘?The Poisonous Plants in NZ’ by H E Connor; illustrated by Nancy M Adams, Government Printer, 1977 and ‘?Maori Healing and Herbal’ by Murdoch Riley, Viking Sevenseas, 1994 – ISBN 0 854 67095 5

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    Thanks Anna.
    I will let you know if they are reds laying on the ferox;-)
    We did have a Red Admiral in the garden this morning feeding on swan plant flowers and Buddleia.




    flutterbys…lets hope you get lots of Reds! I have found its quite easy now to disquinguish Red Admiral eggs to the Yellow ones after watching them lay. To me, the Yellow Admirals eggs look delicate, and the Red Admiral ones are more sturdy looking, and seem to appear a darker green colour.
    The yellow ones glisten more in the sun too…very unscientific I know, but I find it interesting:)


    Hi, Ongaonga is not to be eaten or used in medicine, the toxins are not able to be classified as safe.

    Urtica Incisa can be eaten of our native nettles.




    We have 2 lovely specimens of U. ferox growing in our gardens.
    Either the Red Admiral or the Yellow Admiral seem to be laying on them;-)




    I found a really big healthy one in Karamea near a walking track that was just starting to ripen the seed.



    I had never found any tree nettles in bush near Thames for 11 past years.




    Hello Edward

    Feel free to phone me on 09 551 3383 at the weekend, or if you’re out of Auckland, email me jacqui@monarch.org.nz with your phone number and I’ll ring you.





    Hello Jacui,

    I am new to this forum. i noticed that there are plants for the “Stinging” nettles available, how do I order some and how do i pay for it. I am very interested to have some of them, use to cook them in Ireland to make health tea.

    Kind regards

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