Green Mistletoe

Botanical name: Ileostylus micranthus
Synonyms: Loranthus micranthus
Common name(s): Green mistletoe, Pirita

About:
A distinctive native mistletoe forming bushy yellow-green growths on the branches of other trees and shrubs. Ileostylus micranthus is a woody hemiparasite, meaning that although its green leaves carry out photosynthesis, it obtains water and mineral nutrients from a host plant through specialised structures called haustoria. It is unusually adaptable for a native mistletoe, having been recorded from nearly 300 indigenous and introduced host species and sometimes occurring successfully in gardens and urban environments.

Natural habitat:
Primarily found in coastal and lowland forest, shrubland, forest margins and secondary vegetation, although it occasionally extends into upper montane forest. It is particularly associated with open shrubland and regenerating vegetation where suitable host trees and shrubs receive good light.

Growing environment:
Sun, Partial Shade, Wind & Coastal tolerant. Requires a suitable living host plant and generally performs best on well-lit branches in open forest, shrubland, gardens and regenerating vegetation.

Endemic distribution:
Indigenous to New Zealand, occurring throughout the North Island, South Island and Stewart Island/Rakiura. It also occurs naturally on Norfolk Island and is therefore not endemic to New Zealand.

Height:
Usually up to approximately 1 m as a bushy mass growing amongst the branches of its host.

Width:
Approximately 0.5–1 m or more on well-established plants, depending on the host and growing conditions.

Flowering:
September – December
Produces clusters of numerous tiny green to yellow-green flowers, generally only 3–4 mm long.

Fruiting:
December – July
Produces conspicuous fleshy berries approximately 5–8 mm long, ripening yellow to orange. Each fruit contains a single sticky seed.

Uses:
• Native biodiversity planting
• Mistletoe conservation
• Bird habitat and food source
• Ecological restoration
• Forest and shrubland enrichment
• Specialist native plant collections
• Educational and botanical interest
• Increasing structural diversity in native plantings

Appearance:
Growth habit:
A woody, much-branched, bushy hemiparasitic shrub growing directly upon the branches of other trees and shrubs. Creeping external roots extend along the host’s branches, sometimes spiralling around them, and produce numerous haustoria at intervals through which the mistletoe connects with the host’s vascular system.

Young stems are characteristically somewhat square in cross-section.

Leaves:
Leaves occur in opposite pairs and are thick, leathery and hairless. They are extremely variable in shape, ranging from broadly elliptic and slightly ovate to obovate or rhomboid.

The leaf blades are generally 30–60 mm long but may reach about 80 mm, with colours ranging from dark green through yellow-green. Petioles are flattened and slightly winged.

Flowers:
The small flowers occur in short axillary clusters, typically arranged in groups of three within branched cymose panicles. Each flower has four free greenish to yellow-green petals and four stamens.

Plants may produce male, female or hermaphroditic flowers. The style has a distinctive bent or contorted appearance, a feature reflected in the genus name Ileostylus.

Fruit:
The berries are approximately 5–8 mm long, globular to ellipsoid and become yellow or bright orange when mature. Each contains a single sticky seed approximately 5 mm long.

The sticky material surrounding the seed is critical to establishment, allowing seeds deposited by birds to adhere firmly to host branches.

Ecology:
Ileostylus micranthus is a hemiparasite rather than a complete parasite. Its green foliage manufactures carbohydrates through photosynthesis, while its haustoria penetrate the host and provide access to water and dissolved nutrients.

Unlike some mistletoes that make a single connection with their host, Ileostylus develops external creeping roots along the host branch and forms multiple haustorial attachments. This produces the characteristic network of runners and swollen attachment points beneath established plants.

It has an exceptionally broad host range, having been recorded from nearly 300 native and exotic species. Some regional host preferences occur, and tōtara and related podocarps can be important hosts in some areas.

The orange and yellow berries are eaten by birds, which provide the principal means of seed dispersal. Seeds are deposited or wiped onto branches, where their sticky coating allows them to remain attached while germination begins.

It can be confused with the native mistletoe Tupeia antarctica. Ileostylus can be distinguished by its external creeping roots and multiple haustoria, squarish young stems, characteristically bent flower styles and yellow to orange fruit. Tupeia has internal rather than external haustorial development and typically white fruit, sometimes marked with purple.

Associated habitats:
Coastal forest, lowland forest, forest margins, secondary forest, regenerating scrub, shrubland, urban vegetation and occasionally montane forest.

How to grow:
Unlike conventional plants, green mistletoe cannot simply be planted into soil. It must establish directly on a compatible living host.

Choose healthy, relatively young host branches in a well-lit position. Fresh ripe fruit provides the best chance of success. Gently squeeze the berry until the sticky seed is exposed, then press the seed firmly onto the surface of a suitable host branch.

Dry weather during application is preferable because heavy rain can dislodge newly placed seeds before they adhere properly. Birds may also remove the fruit, so temporary protective netting can sometimes be useful.

Germination itself is generally easy. The difficult stage is successful penetration and attachment to the host. A seed may germinate readily but die several months later if it fails to develop a functional haustorial connection.

Where possible, placing seed onto the same host species—and potentially the same local host type—from which the parent mistletoe was growing may improve establishment.

Propagation:
Propagated from fresh ripe fruit directly onto a suitable host branch.

Remove or squeeze away enough of the fruit flesh to expose the sticky seed, then firmly attach it to the host. Do not sow the seed into ordinary potting mix, as the developing seedling ultimately requires a host connection to survive.

Germination can occur relatively readily, but establishment is unpredictable and may take several months. Multiple seeds placed across several suitable branches provide a better chance of obtaining a successfully established plant.

Cultural use:
Pirita is a Māori name recorded for Ileostylus micranthus. Specific traditional practical uses are not strongly documented compared with many larger native trees and shrubs, but the species forms part of Aotearoa’s distinctive indigenous mistletoe flora and associated mātauranga relating to native forest ecosystems.

Garden value:
An unusual and ecologically valuable addition to established native gardens. Rather than occupying ground space, green mistletoe grows amongst the branches of existing trees and shrubs, eventually forming an attractive rounded mass of leathery green foliage.

Its yellow-orange berries add seasonal colour and provide food for wildlife, while its remarkable parasitic growth makes it an excellent educational and botanical feature. It is also one of the native mistletoes most capable of establishing in modified and urban environments, making it particularly interesting for biodiversity-focused gardens.