‘Hass’ Avocado tree growth on four rootstocks in California. I. Yield and flowering

Two experiments were conducted to assess the relationship between alternate bearing, flowering, fruit set, and fruit growth in mature ‘Hass’ avocado (Persea americana Mill.) in Irvine, California. In the first experiment, trees were grown on four clonal rootstocks (‘Thomas’, ‘Topa Topa’, ‘Duke 7’, or ‘D9’), and data collected on yield, number of fruit per tree, average fruit weight, and the timing and duration of flowering over five seasons. In the second experiment, ‘Hass’ trees were grown on ‘Duke 7’ rootstock and data collected on the rate of fruit retention and fruit volume growth over three years. In Experiment 1, the trees exhibited “on” and “off” years in most cropping cycles. Heavy yields were associated with a higher number of fruit per tree, lower average fruit weight, and early and longer periods of flowering. Although yield varied among rootstocks, especially in heavy crop load years, trees growing on different rootstocks had similar cropping patterns. In Experiment 2, fruit abscission varied over years, but rates of volume increase were similar over years. Low yields in ‘Hass’ avocado trees appear to be related to later and shorter flowering periods and fewer and larger fruit at harvest.

► We measured the yield and flowering patterns of ‘Hass’ avocado on four rootstocks.
► There were no consistent effects of rootstock on flowering, yield, fruit size, or alternate bearing.
► Earlier and longer flowering periods preceded heavy cropping years.
► Heavy yields were associated with high fruit numbers of low weight.