Sustaining Critical Interactions between Functional Species is an 8-year collaborative research project involving ecologists at the University of Canterbury, Massey University and Landcare Research.
Jenny Ladley from Canterbury University has been researching the reproduction of mistletoes on beech trees near Wakefield in the Nelson region.
Together with Philip Lissaman, QEII Nelson-Tasman Regional Representative, Shannel Courtney from the Department of Conservation, and the Tasman District Council, Jenny has also run community field days in Dovedale and Wakefield to establish mistletoes by hand on host beech trees and to encourage the planting of beech seedlings.
The name mistletoe is given to plants that are stem hemi-parasites. These plants can produce their own food through photosynthesis, but they also use specially adapted roots called haustoria to extract water and nutrients from their host plant.
New Zealand is home to eight endemic mistletoe species. Three species, Peraxilla tetrapetala, Peraxilla colensoi and Alepis flavida are known as beech mistletoes because their primary host trees are southern beech (Nothofagus species).
Peraxilla colensoi (scarlet mistletoe) is the largest mistletoe species in New Zealand, sometimes reaching up to 3m in diameter. It has been recorded growing on 16 different host species, but its most common host is silver beech Nothofagus menziesii.
Above: A scarlet mistletoe Peraxilla colensoi seedling. Photo: Matt Walters
The beech mistletoes have all declined in abundance in recent decades.
Reasons for this include loss of habitat, decline in the number of bird-pollinators such as tui and bellbirds, and the detrimental effect of introduced pests, especially possums.
Mistletoe decline is exacerbated by the serious loss of potential host beech trees in settled areas.
‘There are mature silver beech trees with mistletoes up to one hundred years old in core areas such as Dovedale,’ says Jenny. ‘However, because of stock browsing around the beech trees and/or drought, there are few beech seedlings.
‘Old beech trees are dying and there is a gap before the next ones are ready for mistletoe establishment.
'A beech needs to be a couple of metres high and about seven to ten years old before mistletoes will establish.
'So it’s no use waiting until the old trees die. We need an overlap now of young ones growing with the old.’
Philip Lissaman has been involved with the field days through his association with the Tasman Environmental Trust.
‘My personal driver was a wind storm in 2004,’ Philip says.
‘I had been monitoring scarlet and yellow mistletoes in about twelve beech trees along a Dovedale roadside and in one night half of the trees were toppled in the storm. When we lost those beech trees, we also lost the mistletoes.’
‘Our research on mistletoe-host relations shows that beech mistletoes establish best on the same host species they were collected from, and from the same geographic region,’ Jenny explains.
‘At the field days in Dovedale and Wakefield, we pick fruit from the local mistletoes and then plant the seeds on living, healthy branches of beech tree hosts.
‘A mistletoe has thousands of fruits but only a small percentage fall on to a branch and germinate. However, most of the seeds fail to make a successful connection with the water cells in the host beech and die.
‘Then for those that succeed, there’s a long wait as red and scarlet mistletoes can take about seven years to start flowering.’
Above: A 2-3 year old scarlet mistletoe Peraxilla colensoi seedling on silver beech Nothofagus menziesii. Photo: Jenny Ladley
Over 160 people have attended the field days, at which seeds from up to four species of mistletoes were distributed.
Participants were also given beech seedlings to plant to help overcome the gap left by old beech dying.
Jenny adds that all the different agencies working together is a key to the successful field days.
The input from community members will help to sustain our mistletoes and beech trees.’
Above: Jenny Ladley explains how to collect mistletoe seeds and plant them on host beech trees at a community field day in Wakefield. Photo: Philip Lissaman
Download a mistletoe conservation fact sheet (PDF 431KB) with tips on collecting and planting mistletoe seeds, identifying beech trees, and common host trees for each mistletoe species.
Open SpaceTM Magazine No. 73, July 2008 © QEII National Trust