Effects of Rootstock on Tree Mortality Rate and Growth in Young Japanese Pepper (Zanthoxylum piperitum (L.) DC.)

Abstract

Effects of rootstocks on tree mortality rate and canopy volume expansion in young Zanthoxylum piperitum (L.) DC. f. inerme Makino (Budousanshou) Japanese pepper tree were compared among Z. schinifolium Sieb. et Zucc. (Inuzanshou), Z. alatum Roxb. var. planispinum Rehd. et Wils. (Fuyuzanshou) and Fagara ailanthoides Engl. (Karasuzanshou) rootstocks for high viability after grafting and an early canopy establishment.
The tree mortality rate was significantly higher on the Inuzanshou rootstock than on Fuyuzanshou or Karasuzanshou rootstock. All trees on the Inuzanshou rootstock died within 3 years after planting. The volume of tree canopy 5 years after planting was significantly larger on the Karasuzanshou rootstock than on the Fuyuzanshou rootstock. The canopy volume on the Karasuzanshou rootstock was twice as large as that of Fuyuzanshou rootstock. Overgrowth of rootstock was observed on the Karasuzanshou rootstock during the 5- year experiment, but there was no imbalance in the growth rate between rootstock and scion diameter. Numbers of flower clusters produced on 5-year old trees were significantly larger on the Fuyuzanshou than on the Karasuzanshou rootstock.