Eucalyptus Trials for Vineyards

March 2012

Paul Millen is trialling eucalyptus trees to assess their suitability for use as vineyard posts

Paul Millen runs a large tree breeding programme to improve ground durable eucalyptus that are adapted to growing in dryland NZ.

Rural Delivery visited Paul several years ago and looked at posts he had sawn from trees he had obtained, when he was first looking at the potential for having naturally durable timber in vineyards.

At the same time, forestry scientists at the University of Canterbury and other key industry people were becoming really interested in the concept. Paul had identified a group of durable eucalypt species that he had planted in his own research trials and in trials planted by other local landowners who were interested in testing these species.

Within four years of starting that, he was planning a genetic research programme, and that research programme was supported by the Marlborough Research Centre Trust as well as the School of Forestry (University of Canterbury) Proseed NZ Ltd, the Marlborough District Council, Marlborough Lines and the NZ Farm Forestry Association.

In 2008 he got funding from AGMARDT, which launched the NZ Dryland Forests Initiative tree breeding programme, with the first 20,000 trees planted in 2009. In 2010 the NZDFI got Sustainable Farming Fund money.

John and Robyn Cuddon became interested in the idea through having engaged Paul as a consultant to guide the design and landscape planting of their 60ha rural property. As they also owned a vineyard they could see the potential opportunity to grow trees for vineyard posts. As a result over 20 species were planted in trials in 2003 and 2004 with these trees now eight and seven years old respectively.

The research project would not have started with support from people like them and other key landowners.

“I really appreciate that their interest meant that I could include eucalypts in their planting designs and they trusted me in the choice of these species, many untried previously in Marlborough,” Paul says.

This property now demonstrates the potential to grow eucalypt woodlots near to vineyards, which are less than a kilometer away. It also shows that rural residential land, which is easy to access, is an often under utilised and ideal place for growing trees.

“The breeding programme to develop durable eucalyptus species for use in dryland New Zealand is now funded to establish breeding populations for the genetic improvement programme of three main species: Eucalyptus bosistoana, globoidea and quadrangulata.

“The objective is to develop this group of eucalypt varieties that are adapted to being grown in the drier regions of NZ and produce durable timber.

“We started planting breeding populations in 2009 and with Sustainable Farming Fund money we have just completed planting 70,000 trees at 15 sites in NZ, including planting a trial at the Cuddon’s property.  The Cuddons early trials planted in 2004 are now seven year old trees and include 16 different species.

“Every species survived even though some are from places like Queensland, and you would not expect them to survive this far south.  All our best breeding species, E. bosistoana, globoidea, and quadrangulata, are growing well in that early trial.”

“Now we have a new breeding trial of E. quadrangulata. There are 1500 trees in it, and it was planted this last year. It’s about a hectare in that species.

“The Cuddons now have several hectares of eucalypts on their property. This is a pretty typical Marlborough dryland site with rainfall under 700mm per annum. It is dry but fertile, which is why the eucalypts are growing well there.

It can be cold in winter, with moderate frosts.

“What has been key here is being able to plant some of these species in different microclimates, which we have exploited by careful siting. That’s why we were able to find that we can grow a wide range of species.

“We are not looking only for survival, but fast growth rates, good form and high timber durability.   This site was critical for helping us make the decisions about which of the 16 original species to include for in our tree breeding programme.

“It looks as though it takes only five to seven years before these trees produce flowers and seed. So the trials planted seven and eight years ago here are now producing flowers and some have seed.

“Eucalpyts can produce an abundance of seed, but the earliest we may get first generation cross seed is by 2016; that will be a very important milestone.   Certainly by 2017 we can expect to have some improved seed coming on and before 2020 have seed from all our improved species.

“We know the parentage of the mother of every tree we plant in our breeding populations. We sort out the best mothers by looking at all their progeny or children; then look at the best individuals to make our selections of those best individuals with the first selections planned at age 4.5.

“The breeding populations will be thinned at a relatively young age to choose the trees with the best growth and form. Then we want to look at wood quality including early heartwood development and the durability of heartwood.

“The University of Canterbury’s role is significant in this trial. They are currently undertaking a FRST funded research and development programme using special methods and tools to test the wood properties of young pine trees so as to genetically select for improving wood quality. They have developed the science to this and plan to apply this to the eucalypt species. This work is difficult to do on a large scale and with many samples, and at speed. In addition, they are looking at different ways of testing early durability in wood.”

“The traditional way to look at durability of wood is to place wood samples in hotbeds with colonies of fungus or moulds. But keeping colonies of moulds alive is quite challenging, so the University is developing a plan to develop a digester as a faster and more efficient way of evaluating the wood.  This will digest and separate the wood into its chemical constituent parts.

“At the moment no-one understands how the complex hydrocarbon chemicals work which make the wood durable. The chemicals created by the trees are complex but are basically made up of carbon, hydrogen and oxygen.

“If we succeed with developing fast and efficient chemical engineering techniques to evaluate early durability we can then afford to sample from lots and lots of trees, check them and pick the ones with very durable early heartwood.

“We can use dimethyl yellow as an indicator for heartwood, and it changes colour in a very short time if any heartwood is present. I can demonstrate this by showing you these samples.