Coriaria arborea

Coriaria arborea is a highly poisonous and common native shrub or small tree of New Zealand. The common name for the plant is tree tutu, and it is one of the New Zealand species of Coriaria known by the name tutu.^[1][2]

Coriaria arborea
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Cucurbitales
Family:	Coriariaceae
Genus:	Coriaria
Species:	C. arborea
Binomial name
Coriaria arborea Linds.

Coriaria arborea is found in scrub and open areas from the coast to the hills across the country. A straggling plant, it can grow to 20 feet (6.1 m) high. The leaves grow opposite on slender stems while flowers are arranged in drooping racemes.^[3] C. arborea is capable of nitrogen fixation.^[4]

Description

Coriaria arborea has pairs of leaves and long flower spikes

Coriaria arborea is a large shrub that grows pairs of long, glossy leaves on branches, which measure between 50–80 mm (2.0–3.1 in) long. It has flowers that droop from spikes of up to 300 mm (12 in) in length, with black-coloured fruits.^[5] The flower petals are wine-coloured.^[6]

Taxonomy

The species was first described by William Lauder Lindsay in 1868.^[7] Coriaria arborea has two recognised subspecies, Coriaria arborea var. arborea,^[5] and Coriaria arborea var. kermadecensis, the latter found on the Kermadec Islands.^[8]

Ecology

C. arborea plays host to several species of New Zealand endemic moth including Izatha austera, I. churtoni, I. mesoschista and I. peroneanella.^[9]

Distribution and habitat

Coriaria arborea is endemic to New Zealand.^[5] It is the most common species of Coriaria in New Zealand,^[2] and tends to establish itself in disturbed land.^[5]

Uses

In spite of its toxicity, Tutu was consumed by Māori, specifically the extracted juice from the fleshy flower petals. The gathered berries were placed in specially woven baskets (called pū tutu)^[1] lined with the flower heads of Toetoe, acting as a sieve to separate the poisonous seeds from the squeezed juice. The extracted juice is used as a sweetener to foods such as fernroot or was boiled together with seaweed and left to set as a black jelly called Rehia.^[10][1]

Toxicity

The toxin tutin is found in all parts of the plant apart from the fleshy flower petals. Tutu has been responsible for the most cases of livestock poisoning by any New Zealand plant. Dogs and even two circus elephants have been poisoned by the plant.^[11] On occasion human poisoning has occurred through consuming honey where bees had interacted with the plant.^[12]

In 2014, a hiker in Auckland, New Zealand looking to taste supplejack, mistakenly chewed the asparagus-looking young shoot of a tutu. He said he did not actually eat any of the plant because of the revolting taste, but within hours he had multiple tonic-clonic seizures (one of which dislocated his arm) along with labored breathing. Academic experts concluded he was lucky to survive the poisoning. A year later he had recovered fully apart from having some trouble with his memory.^[13]

Honey becomes contaminated when bees collect honeydew secreted by the passionvine hopper insect that feeds off the tutu plant.^[14] People have occasionally been hospitalised or even killed by honey contaminated with tutin. 1974 was the last case of commercial honey poisoning where 13 people were poisoned. Since 1974 there have been nine other cases of honey poisoning, with the most recent occurring in 1991 in the Bay of Plenty and 2008 in the Coromandel.^[15] Periods of drought increase the risk of poisoning.

Gallery

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  Coriaria arborea with developing berries
• 
  Botanical illustration of Coriaria arborea
• 
  Herbarium specimen
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  Tutu fruit
• 
  Tutu leaves