At a glance
Common names: Koromiko, kōkōmuka and willow-leaf hebe, depending on the species and region
Botanical name: Veronica salicifolia G.Forst.
Older scientific name: Hebe salicifolia
Plant family: Plantaginaceae
Native status: Indigenous to New Zealand and also native to parts of southern Chile
Natural habitat: Open scrub, forest margins and other habitats, from low elevations towards the treeline
Plant parts discussed in traditional use: Young leaves, growing tips and leaves used in poultices or decoctions
Constituents of interest: Tannins and other phenolic compounds; research has also identified specialised glycosides in the species
Traditional context: Rongoā Māori, with historical accounts describing use for diarrhoea, dysentery and sores
Modern research: Limited chemical and pharmacological studies, including research on related Veronica species
Important distinction: Traditional use and evidence of astringent activity do not establish that koromiko is a clinically proven treatment for gastrointestinal illness.
Getting to know koromiko
Koromiko is the common name many New Zealanders recognise for native shrubs in the genus Veronica, a group of plants historically classified under the genus Hebe.
Your selected species, Veronica salicifolia, is an upright, bushy shrub with long, narrow, pointed leaves and dense spikes of small white or pale-purple flowers. The flowers can give the shrub a soft, bottlebrush-like appearance, especially when it is in bloom.
The name salicifolia refers to the willow-like appearance of the leaves. The foliage is generally narrower than that of many familiar garden hebes, although leaf shape and size vary between plants.
The species typically grows to around two to three metres tall. It flowers over an extended season, commonly from late spring or early summer into autumn, depending on location and conditions.
Veronica salicifolia is widespread through much of the South Island and is also recorded on Stewart Island. Botanical sources also record it in southern Chile and describe it as indigenous but not endemic to New Zealand.
It generally grows in open sites, scrub and forest, from sea level towards the treeline. It is not restricted to wetlands, although it may occur in damp environments.
Koromiko or kōkōmuka?
The naming of these plants deserves particular attention.
The Māori name koromiko is often used broadly, and historical accounts sometimes combine information about Veronica salicifolia, Veronica stricta and similar species.
The ethnobotanical database Ngā Rauropi Whakaoranga records V. stricta as koromiko in the North Island and northern South Island, while V. salicifolia is associated with kōkōmuka in much of the South Island.
Local naming practices can differ, however, and the terms should not be treated as universally exclusive.
This matters when reading traditional medicine literature. If a historical writer recorded a remedy using the name koromiko without a reliably identified specimen, we cannot always be certain which species was used.
For this guide, the botanical focus is Veronica salicifolia, formerly Hebe salicifolia. Historical uses are identified as belonging to the broader koromiko tradition where the exact species is uncertain.
Koromiko in rongoā Māori
Koromiko has a well-documented place in historical accounts of rongoā Māori.
Rongoā is a broad system of healing that includes plant-based remedies, physical therapies and spiritual dimensions of care. Knowledge has traditionally been transmitted through relationships, observation and practice within whānau and hapū, alongside knowledgeable practitioners.
It is not simply a collection of recipes. The significance of plants, how they are gathered and prepared, and the wider circumstances of their use may vary between communities.
Historical ethnobotanical records describe koromiko leaves and young shoots being used for digestive complaints, particularly diarrhoea and dysentery. Some accounts also refer to preparations for sores and ulcerated skin.
These records are notable because they repeatedly identify digestive complaints as an important reason for using the plant. Koromiko was also used during the twentieth century, including accounts of dried leaves being sent to Māori servicemen overseas during the Second World War.
Such records provide an important view of historical practice, but they need to be interpreted carefully. They do not establish a universal preparation method, a reliable dose or the rate at which the remedy worked.
Nor should modern readers assume that a use attributed to koromiko necessarily applies to every plant sold or labelled under that common name.
A respectful approach recognises the importance of Māori knowledge while being clear about the limitations of historical descriptions and the additional evidence required for a modern medicinal recommendation.
Traditional digestive uses
The best-known traditional medicinal use associated with koromiko is for diarrhoea and dysentery.
Historical records describe the young leaves or growing tips being chewed, as well as preparations in which the leaves were boiled or used in a decoction. The resulting preparations were traditionally associated with reducing excessive bowel movements.
The records are particularly interesting because some historical writers distinguished between chewing the fresh leaves and drinking an infusion or decoction. This suggests that the form of preparation was considered important in traditional practice.
However, these accounts are not modern comparative trials. Differences in preparation, plant identification, the original cause of the symptoms and other circumstances make it difficult to determine how consistently the remedies worked.
Why would an astringent plant have been used?
An astringent is a substance that causes tissues or proteins to contract or precipitate. In herbal traditions, astringent plants have often been associated with managing excessive secretions or discharge.
Tannins are one group of plant compounds capable of producing astringent effects. They bind to proteins, which can alter the texture of tissues and contribute to the characteristic dry, puckering sensation experienced when consuming certain tannin-rich plants.
The astringent properties attributed historically to some koromiko species provide a possible explanation for their traditional association with diarrhoea.
That explanation is biologically plausible, but it does not establish that chewing V. salicifolia will safely or effectively treat the underlying causes of diarrhoea in people.
In particular, dysentery can involve serious infection and intestinal inflammation. Reducing bowel movements would not necessarily eliminate the cause, and delaying medical assessment can be dangerous.
Historical use for skin complaints
Ethnobotanical sources also record the bruised leaves of koromiko being applied as poultices to ulcers and sores.
These applications reflect the broader use of native plants in traditional wound and skin care. Nevertheless, the historical record does not show that a homemade koromiko poultice is sterile, prevents infection or promotes healing to a clinically established degree.
Modern wound care must account for the depth of the injury, infection risk and the possibility of complications. Traditional accounts are valuable historical information, not a substitute for evidence-based care of serious wounds.
What does koromiko contain?
The chemistry of Veronica species is varied and complex. Researchers have investigated tannins, specialised glycosides and other naturally occurring compounds in plants historically grouped under the name Hebe.
The composition of one species should not be assumed to apply identically to another, and findings from a concentrated laboratory extract are not equivalent to the effects of consuming the whole leaf.
Tannins
Tannins are a diverse group of polyphenolic compounds found in many plants. They can bind to proteins and contribute to the astringent qualities of certain leaves, bark, fruits and beverages.
Historical chemical records report tannins in koromiko leaves. Their presence provides one possible explanation for why some koromiko species acquired a reputation as astringents.
A 1967 pharmacological study examined four New Zealand Hebe species, including Hebe stricta. Researchers found condensed tannins among the major constituents of the leaves and twigs studied. Their experiments indicated that the constipatory reputation of H. stricta could be explained in part by its tannin content.
An important limitation: that study did not examine Hebe salicifolia among its four test species. Its findings therefore provide related-species evidence, not direct proof of the chemical composition or clinical effects of V. salicifolia.
Mannitol
The same 1967 study identified D-mannitol as a major constituent in the four Hebe species it investigated.
Mannitol is a sugar alcohol found in various plants, fungi and other organisms. It has several uses in food and pharmaceutical manufacturing, but its effects depend on the quantity consumed and the context.
The finding should not be used to assume that all koromiko species contain the same amount of mannitol. Nor does the presence of mannitol establish a therapeutic benefit for a whole-leaf preparation.
Specialised glycosides
A chemotaxonomic study of plants in the tribe Veroniceae examined specialised compounds that help scientists understand relationships among species.
Researchers identified compounds in Veronica salicifolia, including hebeoside and members of a group of iridoid glycosides. These findings contribute to understanding the plant's chemistry and its relationship to other species in the group.
Hebeoside is a specialised natural product with a complex structure. Its identification does not by itself establish that it is responsible for the plant's historical medicinal use.
To demonstrate that a particular compound produces a beneficial effect, researchers would need to study its biological activity, exposure, safety and relevance to the preparation being used.
Why chemical composition varies
A plant's chemical profile can be influenced by species, plant age, growing conditions, the part collected, season and the way the material is dried or extracted.
An aqueous infusion and an alcohol-based extract may contain different proportions of compounds. The concentration in a laboratory sample may also differ considerably from the concentration obtained from an ordinary fresh or dried leaf.
These variations matter whenever laboratory findings are used to discuss a traditional remedy or commercial botanical ingredient.
What does modern research tell us?
The scientific evidence for koromiko is much smaller than the historical literature might suggest. There are useful chemical and pharmacological observations, but the research base does not establish a safe and effective modern treatment for diarrhoea or dysentery.
The pharmacology of tannins in related species
The 1967 study by Grady and colleagues examined dried leaves and twigs from Hebe stricta, H. odora, H. bollonsii and H. corriganii.
The researchers identified D-mannitol and condensed tannins as major constituents, then investigated the pharmacological properties of tannin fractions from H. stricta and H. odora.
Their findings supported the view that the constipatory effect historically attributed to H. stricta was related to its tannin content.
This is an example of traditional observations being investigated through chemical and pharmacological methods.
However, it is not direct clinical evidence for V. salicifolia. Different species can vary in their chemistry, and results from experimental tannin fractions do not establish the safety or effectiveness of a whole plant preparation in people.
Research into the chemistry of Veronica salicifolia
Chemotaxonomic studies have examined the glycosides and other compounds found within Veronica and related genera. In V. salicifolia, researchers identified hebeoside, a specialised glycoside that helped characterise the species chemically.
Such work has value for plant taxonomy, natural-products chemistry and identifying potential directions for further research.
It does not show that hebeoside treats diarrhoea, infection or inflammation. Nor does it establish the dose, bioavailability or safety of using the whole plant medicinally.
Is there good human clinical evidence?
The sources reviewed for this guide do not establish convincing human clinical evidence that V. salicifolia safely and effectively treats diarrhoea, dysentery or skin conditions.
Historical records document traditional use, while chemical studies provide information about the compounds found in selected species. These are important but different kinds of evidence.
Well-designed clinical research would need to examine an accurately identified species, a standardised preparation, appropriate doses and meaningful health outcomes in people. It would also need to assess adverse effects and determine whether the preparation is suitable for the condition being investigated.
The overall picture: Koromiko has a significant traditional medicinal history, and tannins provide a plausible explanation for some historical astringent effects. However, the available research does not justify treating Veronica salicifolia as a proven modern medicine.
Infusions, decoctions and other preparations
Historical koromiko records describe several forms of preparation, including fresh leaves, chewed young shoots, infusions, decoctions and poultices.
These methods can produce different exposures to the plant's constituents, which is one reason they should not be treated as interchangeable.
Fresh leaves and young shoots
Some traditional records describe chewing young leaves or growing tips and swallowing the expressed juice.
Such accounts are important when documenting the history of rongoā, but they are not a contemporary dosing recommendation. The species may not have been identified precisely in every historical report, and reliable modern safety and effectiveness data are limited.
Infusions and decoctions
An infusion generally involves steeping plant material in hot water, while a decoction involves simmering or boiling it. The temperature, time, plant-to-water ratio and plant part can influence what is extracted.
Historical descriptions of koromiko do not establish a standardised medicinal product. A homemade infusion may vary considerably from one preparation to another, so it cannot be assumed to deliver a consistent dose.
Poultices
A poultice is a moist preparation applied externally. Historical sources describe bruised koromiko leaves being used for sores and ulcers.
An unverified plant poultice is not a sterile dressing. It should not be applied to deep, infected or serious wounds, and plant material should not be introduced into the eye or other sensitive tissues.
For modern topical products, appropriate hygiene, product stability, ingredient quality and evidence for the intended use all matter.
Growing koromiko
Veronica salicifolia can be an attractive addition to suitable native gardens. Its narrow foliage and spikes of pale flowers provide a different appearance from many compact ornamental hebes.
The species typically grows as a bushy shrub in open habitats, scrub and forest margins. It is found across much of the South Island and in suitable habitats at a range of elevations.
For a garden planting, choose a position that matches the plant's local growing requirements and provides adequate space for its mature size. A reputable native-plant nursery can help identify a suitable specimen and clarify which Veronica species is being sold.
Koromiko is also relevant to restoration planting, but local provenance and ecological suitability should be considered when selecting plants for a particular site.
Growing a shrub for its flowers and ecological value is different from collecting it for medicinal use. A garden plant is not automatically suitable for ingestion, especially if it has been sprayed or grown in an unsuitable environment.
Harvesting and respecting native plant knowledge
Before harvesting any native plant, establish who owns the land, whether permission is needed and whether local restrictions apply.
Koromiko's common-name ambiguity makes identification particularly important. A label saying “koromiko” alone may not provide enough information to establish that the plant is Veronica salicifolia.
If the aim is to learn about rongoā Māori, knowledge should be approached in its cultural context. Practices can vary between iwi, hapū, whānau and practitioners, and historical accounts do not capture everything involved in a living tradition.
For botanical or research use, record the species, plant part and collection location accurately. This is essential when comparing chemical findings or interpreting research involving more than one related species.
Responsible harvesting also includes avoiding unnecessary damage to the shrub and respecting the wider ecosystem.
Safety considerations
Koromiko's history of use for gastrointestinal complaints makes it especially important to distinguish historical use from modern self-treatment.
Diarrhoea and dysentery: Diarrhoea has many possible causes, including infections that may require specific medical care. Dysentery, bloody diarrhoea, severe abdominal pain, high fever or signs of dehydration warrant prompt assessment. Do not rely on koromiko to treat these conditions or allow it to delay appropriate care.
Constipation: Historical reports associate some koromiko species with a constipatory or astringent effect. This is not a reason to use the plant to regulate bowel movements, and it may be inappropriate for someone who already has constipation.
Children: Children can become dehydrated quickly during diarrhoea. Do not give children homemade koromiko preparations based on historical recipes. Seek appropriate health advice, especially for infants or children with persistent symptoms.
Pregnancy and breastfeeding: Reliable safety information for medicinal preparations of V. salicifolia is insufficient. Avoid medicinal use during pregnancy or breastfeeding without advice from an appropriate health professional.
Medicines and ongoing health conditions: Clinical interaction data are limited. If you take regular medicines or have an ongoing health condition, discuss a specific botanical product with a qualified health professional or pharmacist.
Skin and wound care: Do not apply homemade plant poultices to serious, deep or infected wounds. Seek appropriate medical attention for wounds that are not healing or that show spreading redness, increasing pain, swelling or discharge.
Correct identification and quality: Never rely on common names alone when selecting a plant for medicinal purposes. The identity, preparation, storage and cleanliness of the material all affect its suitability.
These cautions do not negate the importance of traditional knowledge. They recognise that medicinal recommendations for contemporary use require reliable identification, appropriate safety information and evidence relevant to the intended purpose.
Understanding koromiko's place in modern herbal practice
Koromiko illustrates why a good herbal guide must bring several kinds of information together.
Botany helps establish which species is being discussed. Ethnobotany preserves records of how people used the plant. Phytochemistry investigates its natural constituents, while pharmacology explores the biological activity of particular compounds or preparations.
Clinical research is needed to determine whether a preparation provides a meaningful health benefit in people and whether its risks are acceptable.
These forms of evidence can inform one another, but one cannot replace the others.
In koromiko's case, historical sources repeatedly record its use for diarrhoea and dysentery. Tannins provide a plausible basis for astringent activity in some related species, and chemical studies have identified distinctive compounds in V. salicifolia. Yet the evidence does not establish a standardised preparation that can be recommended as a proven treatment.
An informed approach respects the plant's cultural significance and scientific interest without making claims that exceed what the evidence supports.
In summary
Koromiko is a widely recognised name for native Veronica shrubs in Aotearoa New Zealand. The plant specified here, Veronica salicifolia (formerly Hebe salicifolia), has narrow willow-like leaves and pale flower spikes, and is widespread across much of the South Island.
Historical ethnobotanical records describe young koromiko leaves and shoots being used for diarrhoea and dysentery, alongside poultices for sores and ulcers. However, these reports sometimes cover V. stricta and other related species as well, so not every traditional use can be attributed with certainty to V. salicifolia.
Tannins have been identified in related Hebe species and provide a plausible explanation for their astringent properties. Chemical studies have also identified specialised glycosides in V. salicifolia, but these findings do not prove a clinical medicinal effect.
Koromiko is an important part of New Zealand's ethnobotanical heritage. The most responsible way to understand it is through accurate plant identification, respect for rongoā Māori, careful interpretation of research and appropriate medical care when symptoms are serious or persistent.
Sources and further reading
1. New Zealand Plant Conservation Network. Veronica salicifolia — botanical description, current taxonomy, distribution, habitat and flowering. https://www.nzpcn.org.nz/flora/species/veronica-salicifolia/ 2. Ngā Rauropi Whakaoranga – Manaaki Whenua – Landcare Research. Veronica salicifolia, Veronica stricta and similar spp. Koromiko. Kōkōmuka. Historical ethnobotanical records and clarification of names used for related species. https://rauropiwhakaoranga.landcareresearch.co.nz/names/5b284386-e5e5-40d3-b677-5094a18152b6 3. Te Papa Tongarewa. Māori medicine. Historical and cultural overview of plants used in rongoā Māori, including koromiko. https://www.tepapa.govt.nz/digital-museum/explore-digital-museum/maori/maori-medicine 4. Grady, J., Lewis, J. J., Martin-Smith, M., Muir, T. C. and Subramanian, G. (1967). “Chemical and pharmacological observations on some Hebe species.” Journal of Pharmacy and Pharmacology, 19(2), 87–94. https://doi.org/10.1111/j.2042-7158.1967.tb08042.x 5. Chemotaxonomy of Veroniceae and its allies in the Plantaginaceae. A study of glycosides and other natural products in Veronica and related genera, including V. salicifolia. https://pubmed.ncbi.nlm.nih.gov/16386770/ 6. Health New Zealand. Rongoā Māori. An overview of traditional Māori healing and the wider context of rongoā practice. https://www.healthnz.govt.nz/health-topics/tests-and-treatments/rongoa-maori 7. Science Learning Hub. Rongoā Māori. Educational background on traditional plant use and the importance of appropriate knowledge when preparing native plants. https://www.sciencelearn.org.nz/resources/185-rongoa-maori This guide is educational and is not a substitute for individual medical advice or guidance from a qualified rongoā Māori practitioner.