Maturation, topophysis and other factors in relation to rooting in Larix.

Abstract

We examined effects of mist quantity, topophysis (origin of cutting in the crown of 6-year-old trees), maturation state of the donor stock, and time of sticking on rooting and root system quality of cuttings representing five full-sib hybrid larch families obtained with Larix decidua Mill., L. laricina (du Roi) K. Koch, and L. kaempferi (Lamb.) Sarg. (Sieb. and Zucc.) Gord., as parents. Mist frequency, supplemental watering and family all had highly significant effects on percentage of cuttings rooting and root system quality. The high-frequency misting regime yielded both higher rooting percentages and higher quality root systems than the low-frequency regime without supplemental watering. Supplemental watering of the rooting medium in the low-frequency misting regime increased both percent rooting and root system quality to values comparable with those obtained by cuttings in the high-frequency misting regime. Rooting of cuttings from the top, middle and bottom whorls of 5-year-old plantation grown trees tended to decline with increasing height for three of the five families. Overall, height of cutting origin did not significantly affect rooting, but when analyzed separately, two families exhibited a significant decline in rooting toward the top of the trees. Age of donor ortet (ranging from 1 to 7 years) significantly affected both percent rooting and root system quality. Rooting percentages declined linearly with age, and root system quality declined more sharply than percent rooting. The relatively poor root system quality of cuttings from ortets older than 1 year was closely associated with plagiotropic growth. Softwood cuttings (stuck in mid-July) rooted better than hardwood cuttings (stuck in early September) across all families.