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Getting redwood right for New Zealand

Wade Cornell, New Zealand Tree Grower November 2010.

A call is going out to those interested in redwood development to see if New Zealand can find and grow the best redwoods on the planet. A new redwood trial is being organised incorporating clones selected in New Zealand from seed collected in 2002 by Professor Bill Libby and Wade Cornell. This trial with controls has the potential to indicate the first clones selected for adaptation to our conditions.

We have seen imported clones such as Kuser and Simpson brought here on the basis that they grew well in California. We have since found that good growth in California conditions does not necessarily equate to their growing well here. Even clones selected must go into further trials, otherwise all that could be said is that they grew well on that one site. We also need to ensure that we are not reacting to the dead cow syndrome − a bigger tree because a cow died there a few years before planting.

Of special note will be the inclusion in the upcoming trial of what could be called the ultimate seed collection from the southern and inland portions of California’s natural redwood stands. The collection was partly funded by the US government over concerns about losing some of the northern natural forests due to climate change, and partly by the NZIF.

Seed collection

Pascal Berrill of Humboldt State University, Professor Bill Libby and myself, with a crew of climbers and ground crew, spent a month on the survey and collection last year. Cones were collected from unrelated trees that were the biggest and best from those forests. Cores were taken to check wood properties and determine growth rates. This collection will probably best match New Zealand’s conditions as these redwoods have shown exceptional adaptation to the hottest, driest areas with little or no fog cover. Temperatures can be over 30oC with rainfall under 1000 mm.

The purpose of these new trials is for New Zealand to find clones that are best suited to our conditions. Then we need to select clones that have excellent wood properties which will ensure high value timber. It is unfortunate that large areas of redwoods, other than trials, have already been planted. Redwood is potentially a very high value timber, but only if the wood has excellent stability and durability with appropriate consistent density.

Some redwood nursery and sellers, while endorsing the need for clones with tested wood properties, have not actually performed those tests or provided results for all the required wood properties. Ask questions and be cautious.

Very variable timber

Redwood is enormously variable with densities that can be as low as balsa wood, or up to 400 kg per cubic metre. Durability can be no better than untreated pine, or up to class 1 durability. Seedlings and untested, or only partially tested, clones that have been planted will probably result in a poor quality resource that will do little for New Zealand’s reputation for a high quality product.

The only market that appears willing to take this type of material is for coffins in Taiwan and Korea. The millions of poor quality variable redwoods already planted are likely to swamp this relatively small low, value market and this is where most of the recently harvested resource has gone.

It will take a dedicated effort for those who eventually grow good clones to try and capture high value markets using quality assurance programmes and certification of stands tested for all wood properties. The other hope for recently planted redwood is to accumulate carbon credits. The viability and longevity of the carbon credit scheme is unpredictable. It should not be the only justification for planting redwoods that do not also have good wood properties and a potential high market value.

Owners of recently planted stands but not trials may wish to consider whether they should spend more time, money, and continue to tie up land in a crop that is may not give a viable return. The good news is that recent planting has demonstrated that redwoods grow well in many of the warm and wet districts of the country.

The trials

Now it is time to get back to basics and plant trials of what will eventually enable us to grow high quality high value wood. Trial participants will need −

  • 2,000 square metres that can be fenced off from stock
  • Commitment to maintaining the trial
  • Willingness to undertake occasional measurements.

Trial participants will have first priority on availability of the clones that this trial generates. For further information and to register to be part of the 2011 trials contact Wade Cornell


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