The commercial use of conifer rooted cuttings in forestry: a world overview

Abstract

Conifer reforestation programs have traditionally been carried out using natural seeding, direct seeding or, more recently, planting with nursery-grown stock. Only within the past decade have rooted cuttings found use in large scale commercial operations. To assess the current status of this technology questionnaires were developed and mailed to 50 individuals and organizations around the world. The questionnaires were designed to collect information on: (1) annual production by region and species, (2) objectives of rooted cutting programs, (3) production procedures, (4) field performance of cuttings as compared to seedlings, and other topics.

According to the 36 responses received more than 65 million conifer rooted cuttings are being produced around the world annually, with this number growing rapidly. Fully half the production is in Japan where valuable sugi (Cryptomeria japonica D. Don) cultivars have been vegetatively propagated for at least five centuries. Another 10 million or more cuttings of radiata pine (Pinus radiata D. Don) are being grown in Australia and New Zealand annually. Canada, Scandinavia, and the British Isles together produce about 21 million Norway Spruce (Picea abies [L.] Karst), Sitka spruce (P. sitchensis [Bong.] Carr) black spruce (P. mariana [Mill.] B.S.P.) and other species annually. Programs of one million or less exist in France, West Germany, Belgium, Eastern Europe, the United States and the USSR.

Aside from the Japanese program and some European and Scandinavian programs, where cloning valuable genotypes is the main aim of vegetative propagation, the primary use of rooted cutting technology is for bulk production of genetically improved half or full-sib families. Other uses include production of air pollution-resistant clones in eastern Europe, and production of species which have high commercial value but are difficult to propagate from seed.

Propagation methods have changed little during the past 15 years. Most cuttings are produced from hedges, stock plants, nursery seedlings or field grown trees, and rooted under mist in glass or plastic covered houses. Rooting hormones are often, but not always, used. Roughly half are grown in containers and half bareroot, generally reflecting the preferred method of seedling production in a given region. Although relatively few detailed studies have been reported, field performance of rooted cuttings appears similar to that of seedlings provided donor plants are juvenile. Key research needs are juvenility maintenance, stock plant culture, root system improvement, mechanization, and field testing.