Doc #24 — NZ Flora Reference

COMPUTED DATA: FLORA REFERENCE AND DISTRIBUTION

View the Flora Reference Tables → — 60+ key NZ plants with uses, harvest seasons, nuclear winter resilience; fiber plants; timber properties; and a distribution map.

View the generation script → — Python source code and data sources (DOC, Landcare Research).

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1. FOOD PLANTS

1.1 Kumara (Ipomoea batatas)

Identification: Trailing vine with heart-shaped to lobed leaves. Tuberous roots with purple, orange, or cream skin depending on cultivar. Not native to NZ — brought by Polynesian settlers circa 1250–1300 CE.³

Habitat and distribution: Cultivated in gardens, primarily in the North Island (Northland, Bay of Plenty, Waikato, Gisborne). Requires frost-free growing season of at least 4–5 months and warm soil (above 15 degrees C for planting).

Harvest season: March–May (autumn).

Preparation and uses: Roast, boil, steam, or bake. Stores well in cool, dry, dark conditions (traditional rua kumara — underground storage pits). High in carbohydrates, beta-carotene (orange varieties), and vitamins A and C.

Nuclear winter impact: Severe. Kumara is a warm-season crop and will not tolerate the projected 5 degrees C cooling in most areas. Cultivation may be limited to Northland and sheltered Bay of Plenty sites, or to greenhouse production (Doc #79). Yield reductions of 50–80% are plausible. This is one of the most climate-vulnerable traditional food crops.

Cautions: None. Non-toxic.

1.2 Taro (Colocasia esculenta)

Identification: Large, arrow-shaped leaves on long stalks, growing from a starchy corm. Grows 0.5–1.5 m tall.

Habitat and distribution: Cultivated in warm, moist areas. In NZ, grown primarily in Northland and Bay of Plenty. Requires consistently warm, wet conditions — more cold-sensitive than kumara.

Harvest season: Autumn (March–May), approximately 8–12 months after planting.

Preparation and uses: Corms must be thoroughly cooked to destroy calcium oxalate crystals, which cause severe throat irritation if eaten raw. Boil, roast, or steam. Leaves also edible when thoroughly cooked. Starchy staple with moderate protein content.

Nuclear winter impact: Very severe. Taro is tropical in origin and highly cold-sensitive. Likely restricted to greenhouse cultivation or sheltered Northland locations under nuclear winter conditions.

Cautions: Raw taro is toxic — calcium oxalate crystals cause burning and swelling of the mouth and throat. Always cook thoroughly.

1.3 Puha / Sow Thistle (Sonchus oleraceus and S. asper)

Identification: Soft-stemmed annual or short-lived perennial, 30–100 cm tall, with toothed leaves and milky sap. Yellow dandelion-like flowers. Grows as a common weed throughout NZ in gardens, waste ground, roadsides, and field margins.

Habitat and distribution: Ubiquitous. Found nationwide from sea level to moderate altitude. One of NZ’s most widespread edible plants.

Harvest season: Year-round; best quality leaves in spring and autumn. Plants bolt to seed in summer.

Preparation and uses: Young leaves eaten raw in salads or cooked (boil or steam). Traditionally an important Maori food — often boiled with pork or mutton. Rich in vitamins A, C, and K, iron, and calcium.⁴ Bitter flavour that mellows with cooking.

Nuclear winter impact: Minimal. Puha is a resilient weed that tolerates cold, poor soil, and disturbance. Growth rate will slow but plants will persist. One of the most reliable wild food plants under adverse conditions.

Cautions: None. Easily identified. Avoid harvesting from roadsides that may have been sprayed with herbicides.

1.4 Watercress (Nasturtium officinale)

Identification: Low-growing aquatic or semi-aquatic plant with compound leaves of 3–9 round leaflets. White flowers in spring–summer. Found in clean, slow-moving or still freshwater.

Habitat and distribution: Abundant in streams, springs, ditches, and wetland margins throughout NZ. Naturalised introduction, now extremely widespread.

Harvest season: Year-round; best in cooler months (growth slows in summer heat).

Preparation and uses: Eaten raw in salads or cooked as a green. Exceptionally high in vitamins C and K, calcium, and iron. One of the most nutritionally dense wild plants available in NZ.⁵

Nuclear winter impact: Minimal. Watercress thrives in cool conditions. Spring-fed populations maintain relatively stable water temperature year-round. Growth may actually improve in slightly cooler summers. Highly reliable food source.

Cautions: Harvest only from clean water. Watercress from streams in pastoral areas can carry liver fluke (Fasciola hepatica) — cooking eliminates this risk. Do not confuse with poisonous water plants.

1.5 Pikopiko (Fern Shoots)

Identification: Young, unfurling fronds (fiddleheads) of several native fern species, primarily Asplenium bulbiferum (hen and chickens fern) and Cyathea species (tree ferns). The tightly coiled emerging frond is the edible part.

Habitat and distribution: Native bush throughout NZ; most common in moist, shaded bush, gullies, and forest margins.

Harvest season: Spring (August–November), when new fronds emerge.

Preparation and uses: Boil or steam until tender. Traditional Maori delicacy. Mild flavour, similar to asparagus. Pick when tightly coiled and hairy/scaly. Nutritional value moderate — provides vitamins and dietary variety rather than significant calories.⁶

Nuclear winter impact: Moderate. Fern growth is temperature-dependent but native ferns are adapted to NZ’s cool, moist bush environments. Frond emergence may be delayed and reduced, but established ferns will persist.

Cautions: Harvest only the young, coiled fiddleheads. Do not overharvest from any single plant — leave most fronds to grow. Some overseas bracken fern species contain carcinogens; NZ species eaten as pikopiko are not bracken and are considered safe when cooked.⁷

1.6 Karaka Berries (Corynocarpus laevigatus)

Identification: Large native tree (up to 15 m tall) with broad, glossy, dark green leaves. Produces clusters of bright orange berries (drupes) in autumn–winter.

Habitat and distribution: Common in coastal and lowland forest in the North Island, northern South Island, and Chatham Islands. Frequently planted around pa sites and marae — Maori deliberately spread this species as a food source.⁸

Harvest season: March–June (autumn–early winter).

Preparation and uses: The outer flesh is edible raw (sweet, mucilaginous). The kernel is the primary food source but is highly toxic raw — it contains karakin, a nitro compound that causes violent convulsions. Traditional Maori processing involves: (1) steaming the berries in a hangi or umu for 12–24 hours, (2) soaking the steamed kernels in running water for several weeks (traditionally in flax baskets placed in streams), and (3) drying for storage. Properly processed kernels are a starchy, nutritious food.⁹

Nuclear winter impact: Moderate. Karaka is an evergreen tree with established root systems. Mature trees will survive nuclear winter conditions. Fruiting may be reduced in colder years.

Cautions: TOXIC RAW — SEVERE. Raw or inadequately processed karaka kernels cause violent seizures, brain damage, and death. This species must not be harvested by anyone unfamiliar with the processing technique. Processing knowledge is held by Maori communities, particularly those in areas where karaka trees are culturally associated with former pa sites. Do not attempt to improvise the processing method.

1.7 Ti Kouka / Cabbage Tree (Cordyline australis)

Identification: Distinctive palm-like tree with a narrow trunk and dense clusters of long, narrow leaves at branch tips. White fragrant flowers in spring–summer. Up to 20 m tall.

Habitat and distribution: Widespread throughout NZ in open country, forest margins, wetlands, and riverbanks. One of NZ’s most recognisable trees.

Harvest season: Year-round for stem and root; berries in autumn.

Preparation and uses: Multiple uses — one of NZ’s most versatile native plants. The inner stem (kauru) and root contain starch that is converted to fructose by prolonged slow cooking (24–48 hours in a hangi or earth oven). The resulting food is sweet and energy-dense — historically a significant carbohydrate source for Maori in the South Island, where kumara could not grow.¹⁰ Young leaf shoots are edible. Outer leaves produce usable fiber (see Section 2). The berries are small and mildly sweet, edible but not substantial.

Nuclear winter impact: Low. Ti kouka is exceptionally hardy, tolerating frost, drought, wind, and poor soil. One of the most resilient native food plants.

Cautions: Harvesting the inner stem kills the tree. This is a destructive harvest — only appropriate when the tree can be replanted from seedlings or root divisions. Sustainable use means planting more than you harvest.

1.8 Supplejack Shoots (Ripogonum scandens)

Identification: Native climbing plant (liana) with wiry, intertwined stems. Glossy oval leaves, small white-pink flowers, and red berries in autumn.

Habitat and distribution: Common in lowland and montane forest throughout NZ. Forms dense tangles in bush understorey.

Harvest season: Spring for young shoots; autumn for berries.

Preparation and uses: Young growing tips are edible — cooked like asparagus. Traditional Maori food. Berries are edible but small and not very palatable raw. A supplementary food, not a staple.

Nuclear winter impact: Low. Supplejack is a forest species adapted to cool, shaded conditions.

Cautions: None.

1.8b Other Edible Introduced Plants

Several common introduced plants provide nutritional supplementation:¹¹

• Blackberry (Rubus fruticosus): Abundant pest plant. Fruit (January–March) rich in vitamin C and fibre. Can be dried or preserved.
• Dandelion (Taraxacum officinale): Young leaves edible raw or cooked. Roots can be roasted as a coffee substitute. Widespread.
• Fat hen (Chenopodium album): Common weed. Leaves cooked like spinach; high in protein for a leafy green (approximately 4–5 g protein per 100 g cooked leaf). Seeds can be ground into flour.
• Wild fennel (Foeniculum vulgare): Naturalised in coastal areas. Edible leaves, seeds, and bulb. Flavouring agent. Caution: Do not confuse with hemlock (see section 6.3).

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2. FIBER PLANTS

2.1 Harakeke / NZ Flax (Phormium tenax)

Harakeke is NZ’s single most important domestic fiber resource. See Doc #100 for the full treatment of cultivation, processing, products, and scaling.

Key facts for this reference: Widespread throughout NZ. Leaves up to 3 m long yield muka fiber with tensile strength comparable to manila hemp (440–990 MPa).¹² Traditional Maori processing (haro — scraping with a mussel shell) produces the highest-quality fiber. Industrial-scale mechanical stripping was practised in NZ from the 1860s to the 1970s, with peak production of 20,000–30,000 tonnes per year.¹³ Mechanical stripping requires a drum-and-blade machine driven by water power, steam, or electric motor; the machines are no longer manufactured but can be fabricated from steel plate and bearings by a competent workshop (see Doc #100 for specifications). The plant, the knowledge, and the historical precedent all exist.

Uses: Rope, cordage, twine, sacking, nets, baskets (kete), cloaks (kakahu), sailcloth, paper, caulking, insulation.

Tikanga: Never cut the rito (central shoot) or the two awhi rito (flanking leaves). Harvest only the outer mature leaves. This protocol ensures the plant’s growing point is protected and regrowth continues.

Nuclear winter impact: Moderate growth reduction (estimated 30–60%) but the plant is perennial, hardy, and will persist. Early plantation establishment compensates for reduced per-plant yield.

2.2 Ti Kouka / Cabbage Tree Leaves (Cordyline australis)

The tough, fibrous outer leaves of ti kouka produce a coarser fiber than harakeke, traditionally used for rough cordage, rain capes, and sandals (paraerae). The fiber is weaker than muka but serviceable for non-critical applications.¹⁴

2.3 Pingao (Ficinia spiralis)

A native coastal sedge with golden-orange leaves, used in Maori weaving for decorative elements (tukutuku panels, kete ornamentation). Not a bulk fiber source but culturally and aesthetically important. Grows on sand dunes; currently declining due to habitat loss.¹⁵

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3. TIMBER SPECIES

NZ has both native and introduced timber species of recovery value. Native species are generally slower-growing but more durable; introduced species grow faster and are available in plantation quantities.

3.1 Introduced Plantation Species

Species	Estimated standing stock	Key properties	Primary uses
Radiata pine (Pinus radiata)	1.5–1.8 billion m^3 across approximately 1.7 million hectares16	Fast-growing, versatile, moderate strength. Treated pine resists rot.	Construction framing, fencing, plywood, furniture, firewood, resin extraction
Douglas fir (Pseudotsuga menziesii)	100,000–120,000 hectares17	Strong, straight-grained, good structural timber	Heavy construction, masts, spars, beams
Macrocarpa (Cupressus macrocarpa)	Widespread shelterbelts, estimated 30,000–60,000 hectares (no precise survey; figure based on shelterbelt planting records)	Naturally durable heartwood, rot-resistant	Outdoor construction, fencing, boatbuilding
Eucalyptus (various)	25,000–35,000 hectares18	Dense, hard, strong. Some species very durable.	Firewood (high calorific value), tool handles, construction, fencing

Radiata pine dominates NZ’s plantation forest estate and is the most important single timber resource for recovery. At approximately 1.7 million hectares, the standing stock represents decades of construction timber at recovery-era consumption rates. Pine plantations are concentrated in the Central North Island (Kaingaroa Forest), Bay of Plenty, Nelson, and Otago/Southland.¹⁹

Nuclear winter impact on plantations: Mature plantation trees will survive moderate cooling. Growth rates will slow (estimated 20–40% reduction in volume increment based on temperature-growth relationships for radiata pine).²⁰ Seedling establishment and young tree survival will be more affected. The standing stock is what matters in the near term — it is already grown.

3.2 Native Timber Species

Native species are slower-growing but provide specialised properties not available from plantation species. All native timber is subject to DOC and resource consent requirements under normal law; these requirements may be modified under emergency governance (Doc #144) but sustainable harvest principles remain important.

Species	Properties	Traditional and recovery uses
Totara (Podocarpus totara)	Extremely durable, rot-resistant, fine-grained, easily worked	Carving (whakairo), fencing posts, piles, boatbuilding, water-contact applications
Rimu (Dacrydium cupressinum)	Attractive grain, moderate durability, medium hardness	Furniture, interior joinery, flooring, general construction
Kahikatea (Dacrycarpus dacrydioides)	Odourless, tasteless, lightweight	Food containers, butter boxes (historical), light construction
Kauri (Agathis australis)	Strong, straight-grained, large dimensions, very durable	Boatbuilding, masts, spars, structural beams, furniture
Beech (red, silver, hard — Fuscospora and Lophozonia spp.)	Hard, strong, available in quantity in South Island	Construction, firewood (dense, high calorific value), charcoal production (Doc #102)

Totara deserves particular note: its natural rot resistance makes it irreplaceable for applications requiring wood-to-ground or wood-to-water contact (fence posts, wharves, boat keels). Maori used totara extensively for waka (canoe) construction. Under recovery conditions, totara is the first-choice timber for any application where decay resistance matters and treated pine is unavailable.²¹

Kauri is restricted to the upper North Island (north of approximately 38 degrees S). Existing kauri forests are small remnants of pre-European extent and are currently under threat from kauri dieback disease (Phytophthora agathidicola). Harvesting mature kauri is a last resort — the trees take 600–1,000+ years to reach large dimensions. Salvage timber from already-fallen trees, and buried swamp kauri, are alternative sources.²²

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4. MEDICINAL PLANTS (RONGOA MAORI)

Rongoa Maori — traditional Maori medicine — encompasses a sophisticated pharmacopoeia developed over centuries. The species listed below have well-documented traditional uses and, in several cases, pharmacological research confirming active compounds.²³ Under trade isolation, when imported pharmaceuticals are rationed and eventually exhausted (Doc #116), these plants provide locally available therapeutic options for common conditions.

4.1 Kawakawa (Piper excelsum)

Identification: Small tree or shrub (2–6 m) with large, heart-shaped leaves, often with characteristic holes (from looper moth caterpillars). Black, spike-like fruit clusters. Aromatic leaves.

Habitat: Coastal and lowland bush, North Island and northern South Island. Frost-sensitive.

Uses: Leaves chewed or made into tea for toothache, digestive complaints, and pain relief. Poultice of bruised leaves applied to cuts, skin conditions, and bruises. Contains myristicin and dihydrokawain, which have demonstrated analgesic and anti-inflammatory properties — effective for mild to moderate pain, though substantially weaker than pharmaceutical analgesics (paracetamol, ibuprofen) for acute or severe pain.²⁴ The most widely used rongoa plant.

Preparation: Fresh leaves can be chewed directly for toothache. For a poultice, bruise leaves and apply to the affected area. For tea, steep fresh leaves in hot water (not boiling — excessive heat degrades active compounds).

Cautions: Generally safe in moderate use. Excessive internal consumption is not recommended. Not a substitute for surgical or antibiotic treatment of serious conditions.

4.2 Manuka (Leptospermum scoparium)

Identification: Shrub or small tree (2–8 m) with small, prickly, aromatic leaves and white (sometimes pink) five-petalled flowers. Bark is papery and peeling.

Habitat: Ubiquitous throughout NZ from coast to approximately 1,400 m altitude. Colonises disturbed ground, clay banks, and poor soil. One of NZ’s most abundant native plants.

Uses: Multiple recovery-relevant applications:

• Honey: Manuka honey has clinically demonstrated antibacterial properties due to methylglyoxal (MGO) content. Active against a range of bacteria including Staphylococcus aureus and Streptococcus. Used for wound dressing and burn treatment.²⁵ NZ’s existing beekeeping industry and manuka honey production continue under recovery conditions, though nuclear winter may reduce flowering and honey yield.
• Essential oil: Steam-distilled from leaves and branches using a copper or stainless steel still (requires a sealed vessel, condenser coil, and heat source — see Doc #102 for distillation apparatus construction). Antiseptic and antifungal properties. Usable as a topical disinfectant when medical-grade antiseptics are unavailable, though less effective than chlorhexidine or povidone-iodine for surgical-site preparation.²⁶
• Smoke and steam: Manuka leaves burned or steamed for inhalation to treat colds and respiratory congestion. Traditional use.

Cautions: Manuka honey is not safe for infants under 12 months (botulism risk, as with all honey). Topical use of honey and oil is generally safe.

4.3 Kanuka (Kunzea ericoides)

Often confused with manuka. Kanuka is a closely related species — taller (up to 15 m), with softer, smaller leaves. Similar antiseptic properties in essential oil form but less pharmacological research than manuka. Excellent firewood and tool-handle timber (see Section 5).²⁷

4.4 Koromiko (Veronica salicifolia, formerly Hebe salicifolia)

Identification: Shrub (1–3 m) with long, narrow leaves and spikes of white or pale purple flowers.

Habitat: Widespread in bush margins, river banks, and disturbed ground throughout NZ.

Uses: Leaf infusion (tea) traditionally used for diarrhoea, dysentery, and stomach complaints. One of the most commonly cited rongoa plants for gastrointestinal conditions.²⁸ Contains tannins with astringent properties. Also used externally as a wash for skin infections and ulcers.

Preparation: Steep fresh or dried leaves in hot water. Drink as tea for digestive complaints. Apply cooled tea externally for skin conditions.

Cautions: Safe in moderate use. Not a substitute for oral rehydration therapy in severe diarrhoea or dysentery.

4.5 Horopito / Pepper Tree (Pseudowintera colorata)

Identification: Shrub or small tree (1–3 m, occasionally larger) with distinctive red-blotched, oval leaves. Peppery taste when chewed.

Habitat: Lowland to montane forest throughout NZ, more common in the South Island. Shade-tolerant understorey species.

Uses: Contains polygodial, a sesquiterpene dialdehyde with demonstrated antifungal activity — particularly effective against Candida albicans.²⁹ Traditional use for skin infections, toothache, stomach complaints, and as a spice. Under recovery conditions, horopito is the most important locally available treatment for fungal skin infections and oral thrush when pharmaceutical antifungals are exhausted. Polygodial is effective against superficial Candida infections but is not a substitute for systemic antifungals (fluconazole, amphotericin B) required for invasive fungal disease.

Preparation: Leaves chewed for toothache. Crushed leaf poultice applied to fungal skin infections. Dried and powdered leaves used as a spice (hot, peppery flavour — a substitute for imported pepper).

Cautions: The peppery compounds can irritate mucous membranes. Use externally with care on broken skin.

4.6 Kowhai (Sophora spp.)

Identification: Small to medium native tree with graceful, drooping clusters of bright yellow flowers in spring. Compound leaves with small, round leaflets.

Habitat: Widespread in forest margins, riverbanks, and open country throughout NZ. Several species, all with similar properties.

Uses: Bark and leaves have traditional use for pain, bruising, and wound treatment. Contains cytisine and other alkaloids with pharmacological activity.³⁰

Cautions: TOXIC — use with extreme care. All parts of kowhai are poisonous if ingested in quantity. The seeds are particularly toxic. Children have been poisoned by eating seeds. Traditional Maori medicinal use involved carefully controlled external application and very small internal doses administered by experienced tohunga (specialists). This is emphatically not a plant for self-medication. Include in this reference for completeness, but its use requires expert guidance.

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5. FIREWOOD, TOOL TIMBER, AND UTILITY PLANTS

5.1 Manuka and Kanuka (Firewood and Tool Handles)

Manuka and kanuka are NZ’s best general-purpose utility timbers at small diameter. Dense, hard, and slow-burning, they produce excellent firewood with high calorific value. Straight kanuka stems are suitable for tool handles, fence battens, stakes, and light construction. Manuka is slightly harder and more twisted, better for firewood than structural use. Both species are abundant, regenerate rapidly after cutting, and grow on marginal land.³¹

Nuclear winter impact: Growth slows but both species are very hardy and will persist. Coppicing (cutting to ground level and allowing regrowth) produces a renewable firewood supply on a 5–10 year rotation.

5.2 Introduced Utility Species

• Willow (Salix spp.): Common along waterways. Straight, flexible shoots used for basketry, wicker work, and erosion control. Willow bark contains salicin (aspirin precursor) — chew or brew as tea for mild headache and pain relief, though salicin is slower-acting and less potent than manufactured aspirin (requires metabolic conversion to salicylic acid, with variable dosing from bark).³² Fast-growing; propagates readily from cuttings pushed into moist ground.
• Gorse (Ulex europaeus): Despised as a weed but useful under recovery conditions. Fixes atmospheric nitrogen (improves soil fertility); provides hot-burning fuel; can serve as a nurse crop for native bush regeneration; and its spiny thickets provide livestock-proof fencing. Seeds remain viable in soil for decades.³³
• Pine (various): Beyond timber, pine resin can be distilled into turpentine and rosin (Doc #102). Pine tar from destructive distillation of pine wood is used for waterproofing rope and timber (Doc #102).

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6. TOXIC PLANTS — CRITICAL WARNINGS

Knowledge of NZ’s toxic plants is as important as knowledge of useful ones. Under conditions where inexperienced people forage for food, poisoning risk increases sharply.

6.1 Tutu (Coriaria arborea and related species)

The most dangerous native plant in NZ. A shrub or small tree, widespread in bush margins, roadsides, and disturbed ground throughout the country. All parts except the fleshy fruit pulp contain tutin, a neurotoxin that causes violent convulsions and death.³⁴

• The berries look superficially edible — the juice was traditionally used by Maori (carefully strained through harakeke to exclude seeds), but any ingestion of crushed seeds is dangerous.
• Tutu honey is a risk — bees feeding on tutu-contaminated honeydew can produce toxic honey.
• Action: Public education must include tutu identification. Illustrated guides should be distributed. Children are at particular risk.

6.2 Karaka (see Section 1.6)

Toxic raw. Requires traditional processing. Do not attempt without training from experienced practitioners.

6.3 Hemlock (Conium maculatum)

Introduced species, widespread. Can be confused with wild fennel or carrot. All parts are lethally toxic. Identified by purple-blotched stems, unpleasant musty smell (unlike fennel’s anise scent), and finely divided leaves. Found in waste ground, road margins, and damp areas.³⁵

6.4 Foxglove (Digitalis purpurea)

Common in bush margins and disturbed ground. Contains cardiac glycosides (digitoxin, digoxin) — all parts are toxic and potentially lethal.³⁶ The tall spike of purple bell-shaped flowers is distinctive. Leaves can be confused with comfrey by inexperienced foragers — foxglove leaves are soft and downy on the underside with a wrinkled surface, while comfrey leaves are coarser, bristly, and have prominent veining.

6.5 Ngaio (Myoporum laetum)

Native coastal tree with fleshy, dotted leaves. Contains ngaione, a liver toxin. Occasionally mistaken for a food plant by the uninformed. Primarily a livestock poisoning risk.³⁷

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7. SEASONAL AVAILABILITY AND REGIONAL DISTRIBUTION

7.1 Seasonal Calendar

Season	Available food plants	Available medicinal plants	Notes
Spring (Sep–Nov)	Pikopiko, puha, watercress, supplejack shoots, dandelion	Kawakawa (year-round), koromiko, manuka (flowering begins)	Peak wild greens season
Summer (Dec–Feb)	Puha, watercress, blackberry, wild fennel, fat hen	All medicinal species available	Kumara planting season
Autumn (Mar–May)	Karaka berries, kumara harvest, taro harvest, blackberry (late), puha	Horopito, kawakawa	Bulk harvest and preservation season
Winter (Jun–Aug)	Puha, watercress (both year-round), ti kouka (year-round)	Kawakawa, manuka honey available	Lean season — rely on preserved foods

7.2 Regional Distribution Summary

North Island — northern (Northland, Auckland, Bay of Plenty): Richest plant diversity. Karaka, kawakawa, kauri, nikau palm. Warmest growing conditions — best area for kumara and taro under nuclear winter. Subtropical species persist here longest.

North Island — central and southern (Waikato, Manawatu, Wellington): Good diversity. Harakeke abundant. Most food and medicinal plants available. Kumara marginal under nuclear winter.

South Island — northern (Nelson, Marlborough, Canterbury): Reduced native diversity but abundant introduced species. Strong beech forest (firewood, charcoal). Watercress and puha reliable. Ti kouka common and historically important as a food source in areas too cold for kumara.³⁸

South Island — southern (Otago, Southland): Most limited plant food resources. Cold-hardy species only: puha, watercress, beech (firewood), horopito. Ti kouka was the primary traditional carbohydrate source. Under nuclear winter, this region is the most food-stressed for wild plant resources.

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8. NUCLEAR WINTER IMPACTS ON PLANT AVAILABILITY

The baseline scenario projects 5–8 degrees C average cooling, 10–30% reduced sunlight, and altered precipitation for a period of 5–10 years.³⁹ Effects on NZ flora:

Severe impact (50–80% yield reduction or crop failure):

• Kumara and taro — tropical/subtropical origin, frost-intolerant
• Fruit trees (citrus, avocado, feijoa) — reduced or no fruiting
• Annual food crops dependent on warm growing season

Moderate impact (20–50% yield reduction):

• Harakeke — growth slows, fiber yield per hectare declines, but plant persists
• Manuka/kanuka — growth slows, flowering reduced (affecting honey production)
• Ti kouka — hardy, but growth rate declines
• Native bush fern species (pikopiko) — delayed and reduced emergence
• Karaka — reduced fruiting

Minimal impact:

• Puha, watercress, dandelion — cold-hardy weeds, year-round availability
• Mature timber trees (radiata pine, native species) — standing stock unaffected in short term; growth increment reduced
• Gorse — extremely hardy, nitrogen-fixing, persistent
• Willow — deciduous, cold-adapted, minimal impact

Positive effect (unlikely but possible):

• Watercress may benefit from slightly cooler water temperatures in summer
• Some native bush species may experience reduced insect pest pressure under colder conditions

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9. CROSS-REFERENCES

Document	Relevance
Doc #74 — Pastoral Farming Under Nuclear Winter	Primary food production system; wild plants supplement pastoral output
Doc #82 — Hunting and Wild Harvest	Companion document covering wild animal food sources and edible plant context
Doc #99 — Greenhouse Construction	Protected cultivation for cold-sensitive food crops (kumara, taro)
Doc #99 — Timber Processing	Milling, seasoning, and treating timber species listed here
Doc #100 — Harakeke Fiber Processing	Full treatment of NZ’s primary fiber plant
Doc #102 — Charcoal Production	Charcoal from manuka, kanuka, and beech timber
Doc #116 — Pharmaceutical Rationing	Context for medicinal plant use as pharmaceutical stocks deplete
Doc #119 — Local Pharmaceutical Production	Integration of rongoa Maori plants into local medicine production
Doc #77 — Seed Preservation	Preservation of food plant cultivars and seeds

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FOOTNOTES

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1. Native vascular plant species count from: de Lange, P.J. et al., “Checklist of Indigenous Vascular Plants of New Zealand,” NZ Journal of Botany, 2006. Updated figures from the NZ Plant Conservation Network. Naturalised species from: Howell, C.J. and Sawyer, J.W.D., “New Zealand Naturalised Vascular Plant Checklist,” DOC, 2006.↩︎

2. Riley, M., “Maori Healing and Herbal,” Viking Sevenseas, Paraparaumu, 1994. Also: Brooker, S.G., Cambie, R.C., and Cooper, R.C., “New Zealand Medicinal Plants,” Heinemann, Auckland, 1987. Traditional Maori plant knowledge represents one of the most complete indigenous pharmacopoeias in the Pacific and has been documented in ethnographic literature since the 19th century.↩︎

3. Kumara introduction to NZ: Barber, I.G., “Crops on the border: the growth of archaeological knowledge of Polynesian cultivation in New Zealand,” in Bentley, R.A. et al. (eds.), “Shifting Cultivation and Environmental Change,” Routledge, 2015. Radiocarbon dating places earliest kumara cultivation in NZ at approximately 1250–1300 CE.↩︎

4. Puha nutritional data: Leach, H., “Wild plant use in traditional Maori food,” Food, Culture & Society, 2010. Also: Crowe, A., “A Field Guide to the Native Edible Plants of New Zealand,” Penguin, 2004.↩︎

5. Watercress nutritional profile: USDA FoodData Central. Watercress is exceptionally high in vitamin K (250% DV per 100g), vitamin C (72% DV), and calcium. Also: Crowe, A., 2004 (see [^4]).↩︎

6. Pikopiko traditional use: Best, E., “Forest Lore of the Maori,” Government Printer, Wellington, 1942. Also: Crowe, A., 2004 (see [^4]).↩︎

7. Bracken fern carcinogenicity relates primarily to ptaquiloside in Pteridium species. The native fern species used as pikopiko (Asplenium bulbiferum, Cyathea spp.) are not bracken and are not known to contain ptaquiloside. However, specific carcinogenicity testing of NZ pikopiko species is limited. Traditional consumption at moderate levels is considered safe. See: Fletcher, M.T. et al., “Chemistry and bio-activity of pterosins and pterosides,” Nat Prod Rep, 2011.↩︎

8. Karaka berry processing: Best, E., “Forest Lore of the Maori,” 1942. Also: Costall, J.A. et al., “Karaka (Corynocarpus laevigatus) — an important food plant of the Maori,” NZ Journal of Botany, various. Karaka kernels contain the glycoside karakin, which causes convulsions. Traditional processing by prolonged steaming and leaching is well-documented and effective.↩︎

9. Karaka berry processing: Best, E., “Forest Lore of the Maori,” 1942. Also: Costall, J.A. et al., “Karaka (Corynocarpus laevigatus) — an important food plant of the Maori,” NZ Journal of Botany, various. Karaka kernels contain the glycoside karakin, which causes convulsions. Traditional processing by prolonged steaming and leaching is well-documented and effective.↩︎

10. Ti kouka as food: Simpson, P., “Dancing Leaves: The Story of New Zealand’s Cabbage Tree,” Canterbury University Press, 2000. The kauru (cooked ti kouka root and stem) was particularly important in the South Island, where kumara cultivation was marginal or impossible. Some South Island iwi maintained extensive groves of ti kouka for food production.↩︎

11. Edible introduced plants: Crowe, A., “A Field Guide to the Native Edible Plants of New Zealand,” Penguin, 2004. Fat hen nutritional data from USDA FoodData Central (Chenopodium album, cooked). Blackberry, dandelion, and fennel uses from standard foraging references and NZ weeds literature.↩︎

12. Harakeke fiber properties: Carr, D.J. et al., “Fibre from Three Cultivars of New Zealand Flax (Phormium tenax),” Textile Research Journal, Vol. 75(2), 2005, pp. 93–98. See Doc #100 for full treatment.↩︎

13. NZ flax industry history: Hector, J., “Phormium tenax as a Fibrous Plant,” NZ Government Printer, 1889. Also: Scheele, S., “Harakeke: The Rene Orchiston Collection and Identification of Maori Flax Cultivars,” Landcare Research, 2008. Peak production figures from NZ Official Yearbook data, various years 1920–1960.↩︎

14. Ti kouka fiber: Pendergrast, M., “Te Aho Tapu: The Sacred Thread,” Reed Books, Auckland, 1987. Ti kouka leaf fiber was used for rough cordage, rain capes, and sandals but is weaker and coarser than harakeke muka.↩︎

15. Pingao ecology and cultural use: de Lange, P.J. et al., “Ficinia spiralis (A.Rich.) Muasya,” NZ Plant Conservation Network. Pingao is classified as “At Risk — Declining” due to coastal habitat loss and competition from introduced marram grass.↩︎

16. NZ plantation forest data from: Ministry for Primary Industries, “National Exotic Forest Description,” various years. https://www.mpi.govt.nz/ Radiata pine accounts for approximately 90% of NZ’s 1.7 million hectares of planted production forest.↩︎

17. NZ plantation forest data from: Ministry for Primary Industries, “National Exotic Forest Description,” various years. https://www.mpi.govt.nz/ Radiata pine accounts for approximately 90% of NZ’s 1.7 million hectares of planted production forest.↩︎

18. NZ plantation forest data from: Ministry for Primary Industries, “National Exotic Forest Description,” various years. https://www.mpi.govt.nz/ Radiata pine accounts for approximately 90% of NZ’s 1.7 million hectares of planted production forest.↩︎

19. NZ plantation forest data from: Ministry for Primary Industries, “National Exotic Forest Description,” various years. https://www.mpi.govt.nz/ Radiata pine accounts for approximately 90% of NZ’s 1.7 million hectares of planted production forest.↩︎

20. Radiata pine temperature-growth relationships: Kirschbaum, M.U.F. and Watt, M.S., “Use of a process-based model to describe spatial variation in Pinus radiata productivity in New Zealand,” Forest Ecology and Management, 2011. Growth is strongly temperature-dependent, with the optimum around 18–20 degrees C.↩︎

21. Totara durability and traditional use: Bergin, D. and Steward, G., “Kauri: Ecology, Maturity, Uses and Conservation,” NZ Indigenous Tree Bulletin No. 2, NZFFA, 2004. Also: Best, E., “The Maori Canoe,” Government Printer, Wellington, 1925. Totara heartwood is one of the most naturally durable timbers in the world, lasting 50–100+ years in ground contact without treatment.↩︎

22. Kauri ecology and dieback: Beever, R.E. et al., “Kauri (Agathis australis) under threat from Phytophthora?” Phytophthoras in Forests and Natural Ecosystems, 2009. Kauri dieback disease is a significant additional threat to this species. Salvaged swamp kauri (buried for 1,000–50,000+ years in Northland bogs) is an alternative timber source that does not require felling living trees.↩︎

23. Rongoa Maori pharmacology: Brooker, S.G., Cambie, R.C., and Cooper, R.C., “New Zealand Medicinal Plants,” Heinemann, Auckland, 1987. Also: Williams, L.R. and Lusunzi, I., “Essential oil from Leptospermum scoparium: chemical composition and antimicrobial activity,” Phytotherapy Research, 2005.↩︎

24. Kawakawa pharmacology: Lal, M. et al., “Kawakawa (Macropiper excelsum): a review of a culturally important plant in New Zealand,” NZ Journal of Botany, 2021. Contains myristicin, dihydrokawain, and other bioactive compounds with analgesic, anti-inflammatory, and antimicrobial properties.↩︎

25. Manuka honey antibacterial properties: Molan, P.C., “The antibacterial activity of honey,” Bee World, 73(1), 1992, pp. 5–28. Also: Adams, C.J. et al., “Isolation by HPLC and characterisation of the bioactive fraction of New Zealand manuka honey,” Carbohydrate Research, 343(4), 2008. Methylglyoxal (MGO) is the primary antibacterial compound in manuka honey.↩︎

26. Manuka essential oil: Porter, N.G. and Wilkins, A.L., “Chemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides,” Phytochemistry, 49(7), 1998. Demonstrated antimicrobial activity against a range of gram-positive and gram-negative bacteria and fungi.↩︎

27. Kanuka properties: Perry, N.B. et al., “Essential oils from New Zealand manuka and kanuka,” Phytochemistry, 44(8), 1997. Kanuka oil is distinct from manuka oil in composition but has similar antiseptic properties.↩︎

28. Koromiko traditional use: Riley, M., “Maori Healing and Herbal,” 1994 (see [^2]). Koromiko is one of the most frequently cited rongoa plants in ethnographic literature. Its use for diarrhoea and dysentery is documented across multiple iwi traditions.↩︎

29. Horopito antifungal properties: McCallion, R.F. et al., “Antibiotic substances from New Zealand plants: polygodial, an anti-Candida agent from Pseudowintera colorata,” Planta Medica, 44(3), 1982. Polygodial is a potent antifungal compound. A standardised horopito extract (Kolorex) has been commercially available in NZ as a natural antifungal product.↩︎

30. Kowhai alkaloids: Bick, I.R.C. and Leow, H.M., “Alkaloids of Sophora microphylla,” Australian Journal of Chemistry, 31(9), 1978. Cytisine is pharmacologically active (nicotinic receptor agonist) and toxic in quantity. Traditional Maori medicinal use was carefully controlled.↩︎

31. Manuka and kanuka as firewood: Marden, M. and Rowan, D., “Protective value of vegetation on tertiary terrain before and during Cyclone Bola,” NZ Journal of Forestry Science, 23(3), 1993. Also: standard NZ firewood references. Manuka and kanuka have calorific values of approximately 19–21 MJ/kg (air-dried), comparable to hardwoods. Both species coppice readily.↩︎

32. Willow bark as analgesic: well-established pharmacology. Willow bark contains salicin, metabolised to salicylic acid (the precursor of aspirin). Chewing bark or making tea provides mild pain relief. See any standard pharmacognosy reference. NZ has abundant crack willow (Salix fragilis) and other willow species along waterways.↩︎

33. Gorse ecology and utility: Hill, R.L. et al., “Gorse — a weed that is also useful,” NZ Journal of Forestry, 1991. Gorse fixes 100–200 kg N/ha/year through rhizobial symbiosis and can improve soil fertility on degraded land. Calorific value is high (gorse burns hot and fast), making it effective kindling and short-burn fuel.↩︎

34. Tutu toxicity: Connor, H.E., “The Poisonous Plants in New Zealand,” DSIR Bulletin 99, 1977. Tutin causes violent convulsions and can be fatal. Multiple human and livestock deaths are documented in NZ history.↩︎

35. Hemlock toxicity: Connor, H.E., 1977 (see [^28]). Hemlock contains coniine and other piperidine alkaloids. All parts are lethal. Death is by respiratory failure. NZ has multiple documented human deaths from hemlock poisoning, usually from misidentification.↩︎

36. Foxglove toxicity: Connor, H.E., “The Poisonous Plants in New Zealand,” DSIR Bulletin 99, 1977. Cardiac glycosides in foxglove (digitoxin, digoxin) affect cardiac rhythm. Multiple documented poisoning cases in NZ, typically from misidentification of leaves as comfrey.↩︎

37. Ngaio toxicity: Connor, H.E., 1977 (see [^28]). Ngaione is hepatotoxic (causes liver damage). Primarily a livestock poisoning risk but children should be warned away from the fleshy fruits.↩︎

38. Ti kouka as food: Simpson, P., “Dancing Leaves: The Story of New Zealand’s Cabbage Tree,” Canterbury University Press, 2000. The kauru (cooked ti kouka root and stem) was particularly important in the South Island, where kumara cultivation was marginal or impossible. Some South Island iwi maintained extensive groves of ti kouka for food production.↩︎

39. Nuclear winter climate estimates: Robock, A. et al., “Nuclear winter revisited with a modern climate model and current nuclear arsenals,” Journal of Geophysical Research, 2007. NZ-specific estimates from the Recoverable Foundation working paper. See also Doc #74 for detailed agricultural impact assessment.↩︎