The Flower of Hades - A remarkable root parasite

 

Scientific name: Dactylanthus taylorii (Dactylanthus from the Greek meaning ‘finger flower’, referring to the finger like flower stems, and taylorii after R. Taylor, 1805-1873.)

 

Common names: Flower of Hades (Pua o te reinga), Wood Rose

 

Family name: Balanophoraceae (Root parasites)

 

 

Dactylanthus taylorii is a curious plant with an intriguing botanical history. The Maori referred to it as pua o te reinga which is loosely translated to mean flower of the spirit world or as it is more generally known, ‘Flower of Hades’. The Rev. Richard Taylor, after whom the species name is given, came across it in 1845, while on a trek from Taupo to Wanganui. It is currently found in diverse sites from Northland to Wairarapa, with the largest populations recorded in East Cape and the central North Island (volcanic plateau). In the past in Taranaki it was fairly widely distributed but is now mainly known from populations managed by the Department of Conservation in Egmont National Park and the Waitaanga Conservation Area and a few other scattered locations. Within Egmont National Park the plant is concentrated within the upper montane forest zone between 900 to 1200 m above sea level, in damp but well drained sites with fairly open ground cover, near the limits of shrubby vegetation. However, they have also been found in some areas of dense ground cover; it is possible they maybe more common in these sites but are harder to detect.

 

Dactylanthus is New Zealand’s only completely parasitic flowering plant and is the sole southern representative of the Balanophoraceae family in the world. It has no roots or leaves while the main body of the plant is a tuber that can be seen just above the layer of leaf litter. It is sometimes partially moss covered and resembles an irregular woody bulbous hump of up to 30 cm diameter that is covered in wart like nodules. The nodules are in fact that the remnant bases of old flower stems. The Dactylanthus produces flower clusters just above ground level that protrude on tubular stems which are a dull purplish to grey brown, strongly scented, and are the only other visible part of the plant. The flower stems are covered in dull-brown overlapping fleshy scales which resemble leaves but lack stomata (breathing holes) and are non-photosynthetic (lacking the usual green plant ability to produce starch) floral bracts. Flowering occurs from late summer to late autumn while the small nut like fruit containing a single seed takes at least six months to mature. The seed dispersal occurs close (20-80 cm) to parent plants and has a long dormancy period before germination and attachment to a host.

 

This parasitic plant is regarded as a possible ancient connection to the Gondwanaland flora and is believed to have evolved over millions of years of isolation in New Zealand forests to become dependent on the lesser short tailed-bats (Mystacina tuberculata) as its chief pollinator. Male and female flowers are found on separate plants, not necessarily growing close together, so pollen must somehow be carried from the male flower to the female flower. Research involving video surveillance has captured the nectar feeding bats fulfilling this role. Research has also shown that there is a 5:1 male to female flowering imbalance and that the flowers contain a comparatively large quantity of nectar, particularly the male. Ironically it has also been shown that browsing rats sometimes assist in the pollination, but on some occasions they inhibit the process by damaging the flowers.

 

Dactylanthus lives by parasitising the nutrients and water of about 30 different host species of native trees such as mahoe, lancewood, kohuhu, karamu, putaputaweta and wineberry, mainly shorter-lived or early successional forest components. Although Dactylanthus is relatively numerous in some sites the plant and flowers are often overlooked as they are well camouflaged amongst the leaf litter of the forest floor.

Also although sometimes found growing close to the base of a particular tree they may actually be attached to the roots of another individual some metres away. In Egmont National Park the tree hosts are partly a reflection of what is available within the vegetation zone in which the Dactylanthus occur and include toro (Myrsine salicina), broadleaf (Griselinia littoralis), mountain horopito (Pseudowintera colorata), kamahi (Weinmannia racemosa) and others.

 

In Taranaki, as in other parts of the country, Dactylanthus have come under threat through general habitat deterioration and forest clearance, as well as the effects of introduced browsing animals such as possums and rats that destroy the flowers and prevent seed from developing. Possums are even known to dig for the newly emerging flower shoots, consistently browse in a very destructive manner, and represent the most serious threat to the long term conservation of the species.

 

The former, now prohibited, practise of people collecting the “woodrose” as ornaments has also taken a toll. Where the plant attaches to the roots of its host the host root enlarges and forms a ‘placenta-like’ attachment area which is lobed and fluted, this being the portion that resembles a wooden rose. There are also earlier records of the collection and use of the Dactylanthus tuber by Maori for its medicinal properties.

 

Dactylanthus taylorii is currently rated as nationally vulnerable on the official threatened New Zealand Plants list (2008). The Stratford Area Office of the Department of Conservation had records in 2005 for 164 Dactylanthus within Egmont National Park, and 1 record outside the park. Of these plants 130 are caged to prevent browsing damage, and along with uncaged plants they are visited routinely to record and evaluate flowering and seeding and in particular germination success. Work like this and at other sites around the country will hopefully ensure the survival of this special member of the New Zealand flora.

 

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Photos

1
Dactylanthus taylorii tuber on the forest floor

 

2

The woodrose which connects the parasite to the host plant was once harvested to produce ornaments like this (image from parasiticplants.siu.edu)

 

 

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