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Small Poranthera

Poranthera microphylla

At Risk - Naturally Uncommon

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Small poranthera (Poranthera microphylla) is a slender, much-branched little herb up to about 25-30 cm tall, slightly woody at the base, with tiny blue-grey leaves 3-6 mm long and small white to greenish flowers. It is widespread in Australia but in New Zealand is known only from the top of the South Island, where the Flora of New Zealand records it from forest margins in the Maitai, Cobb, Pelorus and Tinline valleys. It is ranked At Risk - Naturally Uncommon because of its restricted range. It belongs to the Phyllanthaceae family and is the only Poranthera recorded in New Zealand. Explore more native flowering plants in our native plant guide.

Small Poranthera (Poranthera microphylla) in its natural habitat
Image credit: Small Poranthera (Poranthera microphylla) - photo by Wikipedia contributors, via Wikipedia

Plant Description

Poranthera microphylla is a slender, diffuse herb, slightly woody at the base, with branches up to about 25 cm long and almost thread-like branchlets. Australian descriptions give heights to 30 cm and describe it as decumbent or upright and densely branched.

The leaves are small, about 3-6 mm long and 2-3.5 mm wide, membranous, oval to spoon-shaped and blue-grey, borne in distant pairs or alternately on short stalks. Plants carry separate male and female flowers on the same plant; the flowers are small, with white sepals tinged green and narrow petals, and are clustered at the stem tips. The fruit is a flattened, rounded capsule with three lobes.

It is the only Poranthera recorded in New Zealand, and its combination of tiny blue-grey paired leaves, thread-like stems and clusters of minute white flowers distinguishes it from other small herbs of Nelson forest margins. In New Zealand, fruit is recorded from November to February.

Quick Facts

Poranthera microphylla quick facts
Scientific Name Poranthera microphylla
Height Up to about 25-30 cm
Spread Small, diffuse plants
Water Needs No reliable information for NZ populations
Light Forest margins; likely light shade to sun
Frost Tolerance Grows in inland Nelson and Marlborough valleys
Salt Tolerance No information available
Growth Rate Fast
Lifespan Annual or short-lived perennial

Climate Best Suited to

In New Zealand it grows in the inland valleys of Nelson and Marlborough, which have warm summers and cool winters. In Australia it occupies a wide range of climates, from temperate to montane.

Regional Suitability

City suitability for Poranthera microphylla
City Climate Suitability
Auckland Low
Wellington Low
Christchurch Low
Dunedin Low

Plant Habitat

In New Zealand, Poranthera microphylla is confined to the top of the South Island. The Flora of New Zealand records it from forest margins in the valleys of the Maitai, Cobb, Pelorus and Tinline Rivers, and NZPCN photographs are from Puponga Farm Park in North-west Nelson and Pelorus Bridge in Marlborough.

Overseas it is widespread in eastern and western Australia and Tasmania, growing in dry montane forest, woodland and grassland. Detailed habitat information for New Zealand populations beyond forest margins was not found in the sources consulted.

Growing Requirements

Soil Requirements

No specific soil information for New Zealand populations was found. In Australia it grows in forest, woodland and grassland soils.

  • Forest-margin soils in Nelson and Marlborough
  • Likely to need open, uncompetitive ground for a small herb

Light Requirements

Its recorded New Zealand habitat is forest margins, which offer partial light rather than deep shade.

  • Forest edges
  • Light shade to partial sun

Water Requirements

Water requirements for New Zealand plants are not documented. Australian populations occur in relatively dry forest and woodland.

  • No reliable New Zealand data
  • Australian habitats suggest moderate drought tolerance

Planting and Establishing

Small poranthera is not grown in New Zealand gardens and is not available from nurseries. Its value is as a rare wild plant, and it should not be collected.

Botanists interested in it should look along forest margins in the Nelson and Marlborough valleys where it has been recorded, taking care not to disturb plants.

Ecological Role

Little is known about its ecology in New Zealand. Plants carry separate male and female flowers, and the small flowers are presumably insect pollinated, but no New Zealand pollination studies were found.

As a small, fast-growing herb of forest margins, it likely depends on patches of open ground at the edges of forest where taller plants do not crowd it out.

Uses & Significance

Garden Uses

It has no practical garden use and is of interest mainly to botanists.

  • Not available in cultivation
  • Of botanical interest as New Zealand's only Poranthera

Ecological Value

It adds to the diversity of Nelson and Marlborough forest-margin herbs and is one of the plants New Zealand shares with Australia.

  • Naturally uncommon indigenous herb
  • Shared with Australia, but rare in New Zealand

Landscaping Uses

This tiny, delicate herb has no role in landscaping and would be lost among other garden plants.

Where restoration work takes place near its known sites, keeping forest margins open and free of smothering weeds is more useful than planting.

Seasonal Care Calendar

Spring

Plants grow and begin to flower; in Australia flowering runs mostly from September to April.

  • Search Nelson forest margins for flowering plants
  • Record sightings on iNaturalist NZ

Summer

In New Zealand fruit is recorded from November to February.

  • Look for small three-lobed capsules
  • Avoid trampling forest-margin herbs

Autumn

Fruiting finishes and plants may die back.

  • Seed is shed near the parent plants
  • Note population sizes for monitoring

Winter

Little is known about its winter state in New Zealand.

  • No action required
  • Keep weeds from overgrowing known sites

When to Prune and How Much

No pruning is relevant. It is a tiny, short-lived herb that is not cultivated.

At wild sites, the only management likely to help is controlling taller weeds that could shade it out.

How to Grow Small Poranthera

No propagation information for Poranthera microphylla in New Zealand was found in the sources consulted; NZPCN gives no propagation notes and the species is not grown by native nurseries. As a small herb that sets plenty of capsules, it is most likely to be raised from seed. Because it is At Risk - Naturally Uncommon in New Zealand, wild material should only be collected with permission and for conservation purposes, and the steps below are general guidance for small herbs of this type rather than a proven protocol. Any seedlings raised should be returned to suitable forest-margin habitat close to where the seed was collected.

From Seed

Capsules ripen from November to February in New Zealand. Ripe capsules split to release very small seeds, so they should be collected just as they begin to open.

  1. Collect ripe capsules from a small number of plants with permission
  2. Dry them in a paper bag to release the seed
  3. Sow on the surface of a fine, free-draining seed mix
  4. Keep lightly moist in bright, indirect light
  5. Grow seedlings on in small pots before planting back at a suitable site

From Cuttings

Cuttings are not documented for this species and are unlikely to be practical because the stems are very slender. Seed should be the first choice.

  1. If attempted, take short soft tips in late spring
  2. Insert into a fine, moist propagating mix
  3. Keep humid and shaded until roots form

Pests & Diseases

No pests or diseases of Poranthera microphylla are recorded for New Zealand.

The more likely pressures on such a small herb are smothering by weeds, changes to forest margins and accidental trampling at its few known sites.

Cultural Significance

No Māori name or traditional Māori use is recorded for this plant in the sources consulted.

It was described by the French botanist Adolphe-Théodore Brongniart in 1833. The genus name comes from the Greek poros, an opening, and anthera, an anther, referring to the way the anthers open, and microphylla means small-leaved.

Bonus Tip

If you find a tiny, wiry, blue-grey herb with minute white flowers on a forest edge near Nelson or Pelorus Bridge, photograph the leaves, flowers and three-lobed capsules and upload them to iNaturalist NZ: records help clarify the status of this little-known plant.

Plant Conservation

Poranthera microphylla is ranked At Risk - Naturally Uncommon (2023) with qualifiers RR (range restricted), SO (secure overseas) and Sp (sparse). It has held a Naturally Uncommon or Range Restricted ranking since 2004.

Its New Zealand populations are few and localised. Protecting forest margins in the Nelson and Marlborough valleys where it occurs, controlling weeds and recording new sites are the main ways to secure it.

Frequently Asked Questions

Where does Poranthera microphylla grow in New Zealand?

It is known only from the top of the South Island. The Flora of New Zealand lists forest margins in the Maitai, Cobb, Pelorus and Tinline valleys, and NZPCN images come from Puponga Farm Park and Pelorus Bridge.

Is small poranthera endemic to New Zealand?

No. It is indigenous to New Zealand but is also widespread in Australia, including Tasmania, where it grows in dry montane forest, woodland and grassland.

What does small poranthera look like?

It is a delicate, diffuse herb with thread-like branchlets, tiny oval to spoon-shaped leaves 3-6 mm long and small white or pink-tinged flowers, followed by small, rounded, three-lobed capsules.

Why is Poranthera microphylla classed as Naturally Uncommon?

It has a naturally restricted New Zealand range in the Nelson and Marlborough area, and is secure overseas, which is reflected in its RR, SO and Sp qualifiers.

Sources and Further Reading

The botanical, growing, and conservation details for Small Poranthera (Poranthera microphylla) on this page draw on the New Zealand plant references below. Consult them for full technical records and the latest distribution data.