Propagation of 285-year-old alley linden (Tilia x vulgaris) trees via long cuttings

摘要

The historical linden (Tilia x vulgaris) alley of the Berggarten Hannover was planted in 1726/1727 and is a famous element of this botanical garden. However, due to reduced viability and reasons of public safety, several trees or the whole alley need to be chopped down in the near future. This study aimed to preserve these historical trees on their own roots by long cutting propagation. Long cuttings were sampled at two positions (base and crown) from 153 trees in July 2012, treated with rooting powder containing 0.5% indole butyric acid and set for rooting under high-pressure fog conditions. Despite the old age of the mother trees, an unexpectedly high percentage (83%) of the 1,194 cuttings formed adventitious roots that did not depend on the vitality of the mother trees or the cutting position. However, basal cuttings were superior in the survival of the first season in the field, with 55% compared to only 36% of cuttings taken from the crown. The plants, representing 140 mother trees, were observed in more detail, and the majority showed vigorous growth, reaching a height of 1.5 m in 2014 and 3.3 m in 2016. Significant differences in height growth and diameter at breast height were recorded for cuttings from the base compared to those from the crown, with better growth of the basal cuttings. After 7 years, in 2019, genotypes of 140 trees were successfully preserved using autovegetative propagation from long cuttings.