Farm Forestry New Zealand

NZFFA Guide Sheet No. 4: The Cypresses

NZFFA, July 2007.

Introduction

The cypresses are amongst the most favoured ‘alternative” timber species in farm forestry circles. They are moderate to lower density softoods (360-380 kg/m3) with light brown to yellowish heartwood and a fine even texture. The heartwoods are notably durable out of the ground. They show excellent stability and have similar properties to Kauri, but with more pronounced growth rings and better durability. Uses include furniture, joinery, panelling, weatherboards and boat building as well as structural and “on farm” uses. In recent years, high prices have been paid for top veneer grade, pruned cypress logs.

The cypresses are amongst the easiest timbers to saw though there can be some difficulties in drying. The logs can be sawn with any radiata pine equipment. There is a good existing market for cypresses, but since most material come from shelter-belts, logs tend to be under-valued. Sawn, clear heartwood is selling at prices up to $2000/m3 for top grade, kiln dried timber. Some markets require heartwood, others will accept sapwood. Japan and other east Asian countries could be very lucrative, future markets for the cypresses which are highly regarded in these countries.

There are 7 or 8 species and a couple of hybrid cypresses that growers might consider, namely Cupressus macrocarpa, C lusitanica, the hybrid Leyland and Oven’s cypresses, C. torulosa, C. arizonica, C. sempervirens, Chamaecyparis lawsoniana, C. nootkatensis and Ch. obtusa.

Cupressus macrocarpa is the best known cypress and has been grown in New Zealand, mainly in shelter-belts, for almost 150 years. In the open it tends to have poor form with heavy branching and multiple leaders. Today it suffers badly from the fungal disease, cypress canker and this is the major limitation throughout the North Island and northern South Island. Canker is especially bad on warmer, exposed and stressed sites. However, on cooler, southern slopes and in the southern South Island it can still be a preferred species. It is a shade tolerant species and when grown under some shade or at high stocking rates form and health are markedly improved. It requires more fertile sites than radiata pine and shows more marked variations in productivity in response to fertility and other site characteristics. It performs well on coastal sites due to its tolerance of salt winds and even salt spray.

On the negative side, fluting of the trunk can be a problem and it is susceptible to 2 tooth borer.

Improved/selected seedlots and clones are available but should be sourced through a reputable nursery.

Cupressus lusitanica (Mexican cypress) is closely related to C. macrocarpa but has better form and is much more canker resistant making it the preferred species on warmer sites (most of the North Island and northern South Island). On the downside, heartwood yields can be low, the species does not handle wind and especially saline winds, well and there is a risk of possum damage. It is genetically more diverse than C. macrocarpa and the Forest Research Institute breeding programme should ensure significant improvement. There are some good C. lusitanica x macrocarpa hybrids.

Hybrid Cypresses already include a number of well proven clones and it is very likely that more will be developed in coming years. Leyland cypresses are hybrids of C. macrocarpa x Ch. nootkatensis with several clones being available. Leighton’s Green is the most common, often used for shelter, but others are preferred in different localities. Check local experience.

They offer some advantages over C. macrocarpa, with somewhat improved canker resistance and better tolerance of wet and wet/dry sites. The timber is of good quality, though has not been widely sawn and used in N.Z.

Oven’s cypress, a single clone of a C. lusitanica x Ch. nootkatensis hybrid, is an exciting prospect though there are not yet any mature trees in N.Z.. It has excellent form, good canker resistance and good timber properties including good yields of heartwood. However, it needs protection from persistent wind and especially saline wind.

Amongst the other species, C. torulosa tolerates very dry sites with good form, health and timber, but is slower growing. C. arizonica is very site tolerant and is an effective shelter species, less favoured for timber. Ch. lawsoniana was once widely grown as a shelter species but is now restricted to higher altitude, cooler, fertile sites by cypress canker. It produces an excellent timber. Ch. obtusa, the revered Hinoki of Japan, is fairly rare in N.Z. but some seedlots have been introduced and it may have possibilities for the Japanese market.

Ch. nootkatensis (Alaskan yellow cedar) is another notable timber species well suited to colder, wet sites but not swamps.

Establishment

Cypresses can be established with either cheaper seedling or more expensive cutting grown stock. Bare rooted stock is generally preferred to container grown material, though on dryer, harsher sites container of plug grown material generally performs better. Planting should be from late autumn to late winter but can be extended into spring with container grown material.

It is important that young seedlings are not smothered by competing vegetation, so releasing is normally done by chemical spraying. Terbuthylazine (Gardaprim) has been the chemical of choice, but on sites dominated by grasses and especially tropical C4 grasses such as kikuyu, paspalum, etc. and also cocksfoot, Gallant should be added. If thistles and other broadleaf weeds are an especial problem Versatil can be used, but at exactly the recommended rates.

These recommendations are: 1.5 ml. Terbuthylazine }
0.3 ml. Gallant } per 1.5m. diameter spot
0.3 ird. Versatil }

It is better not to spray over the top of flushing trees and there have been reports of damage to C. lusitanica from Gallant in such cases.
Repeat spraying in year two may be necessary with severe competition. Generally, cypresses establish as fast, or faster, than radiata pine.

Silviculture

Recommendations for cypress silviculture and regimes vary quite widely. They are a shade tolerant group and form and health tend to be better in a sheltered, shaded or light-well situation. Alternatively, on more open sites they perform better interplanted with pines or planted at high stocking rates (perhaps 1500 sph plus). If interplanting with pines, it will probably be necessary to do some pine pruning and do not allow them to smother the cypresses.

Traditionally it has been recommended that cypresses be pruned little and often, with the larger branches in the crown also being removed. Recent work suggests that C.macrocarpa can stand very hard pruning down to a trunk diameter of less than 5 cm., without seriously affecting growth. Such pruning would allow removal of all large branches.

Other recent work by Pascal Berrill at Forest Research suggests that up to 15 to 20 years, the top 400 trees per hectare will grow at much the same rate regardless of the stocking rate. The conclusion is don’t thin too early. Loss of live foliage on the lower branches of the green crown is considered a better guide for thinning. Try to avoid too many dead branches with their associated dead, encased knots and associated timber down grade.

Cypresses have very even wood properties from pith to bark without the unstable, juvenile core characteristic of radiata pine. Thus, young cypresses generally mill well (even down to 12 -15 years of age), though yield limited amounts of heartwood. Short rotations at High stocking rates (600 trees per hectare plus), or production thinning, are realistic options. However, if the target is clear, knot free heart wood, especially in larger dimensions, then you need lower final stocking rates, perhaps 200 -300 trees per hectare and longer rotations. Cypresses, especially C. macrocarpa, can grow to large diameters, hold high basal areas and standing volumes and show impressive increments on appropriately fertile sites even at low stocking rates.

For heart clearwood regimes aim for a rotation of 35 -40 years.

The N.Z. Farm Forestry Assn. has an active Cypress Development Group with regular field days and newsletters. We would urge current or prospective cypress growers to join up and share their experiences.

Publications that may help prospective growers are:

The Cypress handbook, available on the Farm Forestry website here.
The Cypress Growers Handbook by Stephen Brailsford, Brailsford Management Ltd, Old Tai Tapu Road, RD 2, Christchurch.
Forest Research Bulletin No 124, Part 9 “The Cypresses”, N.Z. Forest Research, Private Bag 3020, Rotorua.