Macrocarpa stories – more needed
Allan Levett, New Zealand Tree Grower November 2009.
The Cypress Development Group decided at its AGM in Gisborne to carry out some joint research with Scion on macrocarpa. Macrocarpa produces a highly regarded timber in New Zealand and those of us who grow the tree successfully love to work with it. We want to discover where in the country we should grow it and where not to, in particular where canker affects it most and where least.
We need many sites up and down the country where we can take accurate measures of all the conditions likely to affect the growth or death of macrocarpa such as age, temperature, humidity, frost, wind, rainfall, drainage, soil composition, pruning, and so on. We would like people to send us their stories about good and bad experiences with macrocarpa.
We formed a small group to get the research going and started by telling each other macrocarpa stories by email. This series of emails in full from several people retain the lively flavour of each contribution and will probably be circulated as a newsletter. It seemed to be a good idea to produce summary of some of them in this article.
Graham Milligan described dying macrocarpa stands in Southland where currently, it seems there is an epidemic of canker. Nevertheless he reports sound stands under various favourable conditions including the application of boron. Ian Brown was gloomy about growing the trees successfully in the warm, wetter areas north of Auckland and around Pirongia.
Ian had been to California and seen macrocarpas clinging to promontories by the sea on the Monterey Peninsula. One much photographed lone macrocarpa tree may be over 300 years old. He says that these trees are seriously tough, the closest thing he has seen to pohutakawa. It is ironic that a tree that can get its nutrients from rocky crevices and tolerate constant battering from salt-laden winds but is unable to handle a miserable little canker fungus.
A few hundred metres inland in the cool zone Ian saw other trees that had germinated naturally after fire, which may have cleaned out fungi. Elsewhere in the US mainland, and in Japan, Hawaii, Australia, Africa from Kenya down to South Africa, England and France, macrocarpa has been devastated by canker. Consistently, temperature seems to be a common factor.
Prefer cooler eras
Denis Hocking hypothesizes that the macrocarpa around Monterey are remnants of an ancestral cypress that was formerly widespread through California and beyond. He says that they do not like present day California and probably belong to a cooler ice-age era. Cypresses prefer cooler conditions with comparable latitude, like New Zealand.
Denis has seen macrocapas showing good health and form in sheltered sites, sometimes provided by nurse trees, on better well-drained soils on the edge of his own sand dune country. Macrocarpa also grow on steep, cool south-facing slopes in the Wairarapa where the humidity is low even in the warm summers and the average rainfall is about 850 to 950 mm.
Don Tantrum. Richard Thompson, Dean Satchell and Paul Millen all see stress as a key factor. They give examples of trees from their areas of different provenances surviving and succumbing to canker, depending on stress levels from too much wind exposure, warmth, moisture, humidity, over-pruning and canker in the district, and too little nutrient, moisture, drainage and light.
Paul and Denis have seen less canker where macrocarpa is exposed to salt winds. Ian Brown thinks it is the lack of fungi in those winds coming from across the ocean that results in reduced canker in coastal trees rather than the presence of salt.
Much has been said about the good features of macrocarpa timber that make it desirable in the market place for many indoor and outdoor uses. Don Tantrum adds another little-known attribute of the species − durability. Macrocarpa can last over 40 years in the ground.
Durability is greatest in larger branches and trunks, then split wood, followed by sawn timber. He has seen a macrocarpa power pole at least 50 years old and still in use. Macrocarpa will rot at ground level or where it touches some other surface first but will last many years providing it can dry out.
We would like accounts of many sites where macrocarpa has done well or poorly. Please send us your own macrocarpa stories to the secretary of the Cypress development group:
PO Box 23
03 248 5147