VEGETATIVE PROPAGATION OF CONIFERS: XIII. ROOTING OF NORWAY SPRUCE CUTTINGS IN THE GREENHOUSE

Greenhouse propagation of Norway spruce cuttings in various media containing sand and peats resulted in 80% rooting in a peat-humus–sand medium. Canadian peat moss and Swedish peat media were inferior but the weekly addition of potassium acid phosphate and magnesium sulphate solutions to a Swedish peat medium resulted in the rooting of 96% of the cuttings. Beneficial effects of peat humus were related to available nutrient materials. Peat humus extracted with methyl alcohol and acetic acid did not affect rooting, but sodium hydroxide extraction, hot water extraction, and air drying at 110 °C. were harmful. Propagation under suboptimum conditions disclosed markedly beneficial effects from mixtures and mulches of peats, soil, and active silica, the active silica being particularly favourable in the mulched condition.Medium cuttings, 3 to 6 in. long, rooted 96%, and long cuttings, 6 to 10 in., 71%. Uncovered cuttings and those covered with celloglass were superior in their responses to those under either cheesecloth or factory cotton screens.Plant hormone chemicals, when applied in a talc carrier dust, tended to reduce rooting of Norway spruce cuttings; the injurious effects increased progressively with concentration over the range from 500 to 4000 p.p.m. Indolylbutyric acid showed neither damaging nor beneficial effects. Naphthylbutyric acid and potassium naphthylhexoate, while similar in effect, tended to be less injurious than naphthylacetic acid when used over a range of equivalent molecular concentrations. Application of naphthylbutyric acid at the 2000 p.p.m. level in a charcoal carrier resulted in rooting of 98% of the cuttings. Mean root length was increased by the application of 50 p.p.m. each of thiamin and nicotinic acid. While nutrient salts and naphthylbutyric acid, each separately, tended to reduce mean root length, the combination had no injurious effect.