EFFECTS OF VARIOUS ROOTS ON 'CHANDLER' WALNUT CATKIN AND PISTILLATE BLOOM, TREE GROWTH, YIELD, AND NUT QUALITY

‘Chandler’ is the leading English walnut cultivar currently being planted in California. Rootstock selection can have significant effects on the performance of the scion in terms of catkin abundance, tree growth, yield efficiency, and the nut quality attributes of percent edible kernel and kernel color. This rootstock trial was planted in March 1999 in a randomized complete block design with six replicates of two trees per treatment at the California State University Farm in Chico. Six treatments are evaluated; three on English walnut roots and three on paradox walnut roots. Rootstock treatments include: own rooted ‘Chandler’, grafted and not grafted, English ‘Waterloo’, common paradox, ‘Trinta’ paradox, and ‘Px1’ clonal paradox. Own rooted trees have lower catkin abundance and yield efficiency but good nut quality and value. English walnut rootstocks are performing similarly to one another. ‘Px1’ paradox is similar to common paradox in nearly all respects and both stocks produce larger tree size than the ‘Trinta’ paradox rootstock. Own rooted ‘Chandler’ trees could provide an advantage in areas with a high incidence of blackline caused by cherry leaf roll virus since without a Northern California black or paradox rootstock English walnut trees can tolerate the disease.