English walnut rootstocks help avoid blackline disease, but produce less than ‘Paradox’ hybrid

While ‘Paradox’ hybrid seedlings are often the rootstocks of choice for California walnut orchards, there is a resurgence of interest in using English walnut seedlings because walnut blackline disease, which is endemic in many California walnut production districts, does not affect them. We compared the growth and productivity of walnuts on English rootstocks from a variety of sources to those on Paradox rootstock. The growth and productivity of ‘Chandler’ walnut trees were similar among trees on seedling English rootstocks in one trial, but trees on English rootstocks were smaller and had lower production than Paradox hybrid-rooted trees in the other.