Dwarf Mistletoe

Botanical name: Korthalsella salicornioides
Synonyms: Viscum salicornioides
Common name(s): Dwarf mistletoe, leafless mistletoe

About:
Korthalsella salicornioides is a tiny, highly specialised endemic New Zealand mistletoe that lives as a hemiparasite on the branches of other woody plants. It is particularly associated with mānuka (Leptospermum scoparium) and kānuka (Kunzea spp.), although several other native shrubs and trees can serve as hosts.
Plants form distinctive dense masses of succulent, cylindrical, bead-like stems, generally only 3–10 cm long. True foliage leaves are absent, with the green stems taking over the role of photosynthesis. Colour varies considerably from green and yellow-green to reddish-green and orange-green.
Although the visible shoots are very small, the mistletoe has an extensive internal connection within its host. Individual aerial shoots generally persist for around 1–4 years before dying away, after which new growth may emerge from the established internal system.

Natural habitat:
Coastal to upper montane and subalpine forest and shrubland, from near sea level to approximately 1,300 m.
It occurs wherever suitable host plants are present but is most strongly associated with mānuka and kānuka shrublands and forests.
Plants develop directly on exposed branches and branchlets of their hosts and can be surprisingly difficult to detect despite occasionally occurring in considerable numbers.

Growing environment:
Host-dependent, Full Sun to Partial Shade, Exposed & Cool conditions tolerant.
The environmental tolerances of Korthalsella salicornioides are closely linked to those of its host. Its occurrence from coastal shrubland to subalpine vegetation demonstrates considerable climatic tolerance.
It cannot grow independently in ordinary soil and must establish a successful connection with the vascular system of a compatible living host.

Endemic distribution:
Endemic to New Zealand.
Found throughout the North Island from Te Paki southward, as well as the South Island and Stewart Island/Rakiura.
Despite this broad geographical range, it is naturally sparse and often occurs as scattered plants or small localised populations. It can occasionally become locally abundant where suitable hosts are plentiful.

Height:
Usually 3–10 cm from the host branch.

Width:
Individual shoots may form dense masses approximately 10–45 cm across, although size varies considerably depending on the number and arrangement of aerial growths.

Flowering:
October–March.
The flowers are extremely small and inconspicuous. Flowering portions are scarcely distinguishable from ordinary vegetative stems and are approximately 3–10 mm long and about 1 mm wide.
The tiny flowers are easily overlooked without close examination.

Fruiting:
October–May.
Fruits are tiny, fleshy, yellowish, ovoid to almost spherical structures approximately 1.5 mm long.
Mature seeds may be forcibly ejected from the fruit under hydraulic pressure. Their sticky coating subsequently helps them adhere to the bark of another branch. Birds may also contribute to dispersal.

Uses:
• Indigenous biodiversity conservation
• Mistletoe conservation programmes
• Ecological and host-parasite research
• Specialist botanical collections
• Educational displays
• Restoration of complete mānuka and kānuka ecosystems
• Conservation of specialised native plant relationships
It is not suitable for conventional landscaping and should never be collected or removed from wild populations.

Appearance:
Growth habit:
A minute, leafless, succulent hemiparasitic shrub growing directly from the branches and branchlets of its host.
Plants are densely and repeatedly branched, with branches characteristically arising at narrow angles. This produces a compact mass of cylindrical, jointed stems with an appearance somewhat reminiscent of miniature coral or Salicornia.
Visible shoots emerge directly through the host’s bark.
Leaves:
True foliage leaves are absent.
Photosynthesis is instead carried out by the green succulent stems. Individual internodes are cylindrical rather than flattened, generally 3–10 mm long and 1–3 mm diameter.
Each segment narrows toward a finely constricted node surrounded by a small truncate collar up to approximately 0.5 mm long.
The cylindrical internodes are one of the easiest ways of distinguishing this species from New Zealand’s other Korthalsella, which have distinctly flattened stem segments.
Flowers:
The minute flowers are produced directly amongst the stem segments and are barely distinguishable from vegetative growth.
They are approximately 2–3 mm across, with three tepals. Male and female flowers occur on the same plant.
Their tiny size means flowering plants can easily appear to have no flowers at all when viewed from a distance.
Fruit:
Fruits are fleshy, ovoid to globular and approximately 1.5 mm long, becoming yellowish as they mature.
The fruit contains a sticky seed specially adapted for establishing on another host branch.
Rather than simply falling beneath the parent plant, mature seeds can be explosively projected away from it. Once they strike suitable vegetation, the adhesive seed can stick firmly to the bark.

Ecology:
Korthalsella salicornioides is a hemiparasite. It contains chlorophyll and carries out photosynthesis but obtains water and dissolved mineral nutrients through a specialised vascular connection with its host.
Its haustorial system develops internally within the host branch and may form dark green tissues encircling the host’s vascular cylinder. This persistent internal system enables fresh aerial shoots to emerge even after older visible growth has died.
Mānuka and kānuka are its principal hosts, making the conservation of healthy Myrtaceae communities particularly important to the mistletoe’s survival. It has also been recorded from other native plants, including Melicope simplex, Myrsine australis and species of Dracophyllum and Gaultheria.
Loss of host vegetation through land clearance, firewood collection, forestry establishment and other habitat modification can consequently eliminate mistletoe populations even when the mistletoe itself is not directly disturbed.

Associated habitats:
Mānuka shrubland, kānuka forest, coastal scrub, lowland shrubland, regenerating forest, montane scrub, upper montane shrubland and subalpine vegetation.
It is especially characteristic of ecosystems dominated by Leptospermum scoparium and Kunzea species but can occur within other native woody vegetation where suitable hosts are present.

How to grow:
Korthalsella salicornioides is exceptionally difficult to cultivate and cannot be grown as a conventional container or garden plant.
Successful cultivation requires establishment directly onto a suitable living host. Healthy mānuka or kānuka provide the most appropriate hosts when conservation propagation is attempted.
Fresh seed must become attached to suitable young bark and subsequently establish a functional haustorial connection with the host’s vascular tissues. Even when germination occurs, successful long-term establishment is not guaranteed.
Wild plants should never be removed in an attempt to transplant them because separation from their host destroys the physiological connection upon which they depend.

Propagation:
Propagation is specialised and difficult.
Fresh mature fruits provide the appropriate propagation material. The sticky seed is removed or allowed to eject naturally and is then placed directly onto a suitable living branch, preferably mimicking the position and host species used by naturally occurring plants.
The seed must remain attached long enough to germinate and establish its haustorium within the host.
Ordinary seed trays, potting mix, cuttings, division and transplantation of aerial shoots will not successfully reproduce the species.
Because populations are naturally sparse and conservation concerns exist, propagation material should not be collected from wild populations without appropriate consideration or authorisation.

Cultural use:
No well-documented traditional Māori material use specifically attributable to Korthalsella salicornioides is widely recorded.
Its contemporary significance lies particularly in its contribution to the distinctive biodiversity of Aotearoa and the specialised ecological relationships within indigenous mānuka, kānuka and shrubland communities.
Its dependence on living native hosts also demonstrates how conservation of an individual plant species can depend upon protection of the wider plant community surrounding it.

Garden value:
Dwarf mistletoe is primarily a conservation species rather than a conventional garden plant.
Where it occurs naturally on established mānuka or kānuka, it is an exceptionally interesting feature worth protecting. Its minute size, succulent bead-like stems and unusual parasitic lifestyle make it unlike almost any conventional garden plant.
For ecological restoration, its presence can be considered an additional measure of habitat complexity: restoring healthy populations of appropriate host plants provides the habitat from which specialised species such as Korthalsella salicornioides may ultimately persist or re-establish.