The rootstocks ‘Bitters', ‘Carpenter' and ‘Furr citrandarins were developed at the USDA Date and Citrus Station in Indio, California. Having mandarin genetics with different horticultural properties and being more tolerant of calcareous soils than some other commonly used rootstocks, their effect on ‘Pixie' mandarin is being evaluated. These three are being compared to the mildly dwarfing ‘C-35' rootstock and to the standard sized ‘Citrumelo' to see how their growth might be used to control tree size, also to see how well they do in an alkaline soil. In 2014, five of each of the rootstock/'Pixie' combinations were planted in randomized blocks at two different sites on mildly alkaline soils (pH 7.3 -7.8) in the Ojai, CA area. Trees were monitored for growth on a yearly basis. At both sites ‘Citrumelo' is the largest in height with the greatest shoot length. All three of citrandarins are smaller than ‘C-35” at both sites. Shoot length is the shortest for ‘Bitters', ‘Carpenter' and ‘C-35' at both sites. At the site with the highest soil pH (7.8), two of the five ‘Bitters' show iron and zinc chlorosis. The only trees to do so.  This trial will be monitored for another five years to evaluate their performance. Growth characteristics on other varieties of citrus, such as orange and lemon will probably be the same.

Photo: A young Pixie on Bitters.