1990 Volume 59 Issue 3 Pages 487-501
1. In order to determine avocado tree (Persea americana Mill.) bearing behavior in Japan, the cultivars ‘Zutano’, ‘Bacon’ and ‘Fuerte’ were studied in Yamada Orchard, Numazu, Shizuoka, during 1980-′88.
2. Fruits had a sigmoid growth curve, growing rapidly after late June and then slowly after mid August. Growth of seeds was steady June to October and slow thereafter.
3. Flower (fruit) drop had two peaks, first mostly flowers from early May to mid June, and a second peak of mostly small fruits from late May to late June. Flower drop was more severe than fruit drop.
4. Primary branches (bearing shoots) and secondary branches (lateral shoots) elongated rapidly after mid May, then very slowly after late June.
5. Leaf drop had two peaks, the first from mid May to mid June and a second for ‘Bacon’ and ‘Zutano’ from August to late September.
6. Inflorescences were of two types: Indeterminate (with growing tip) and determinate (no growing tip). ‘Zutano’ had more indeterminates; ‘Bacon’ and ‘Fuerte’ inflorescence type tended to alternate from year to year.
7. There were eight types of fruiting branchlets, based on different combinations of vegetative and bearing shoots. Successful fruiting percentage was higher for summer than for spring shoots, for first than for later branches, and for terminal buds than for secondary nodes of flowering branchlets.
8. Fruit set per flower ranged up to 0.038%, with ‘Fuerte’ highest and ‘Bacon’ lowest. Yield alternated from year to year. Both fruit size and number were smaller in years with lower temperatures.
9. Flower bud mortality increased with both time and lower temperature minimum in the -2.5° to -3.5°C range.
10. The major impediment to avocado growing in Japan is low temperature, both winter freezes and flowering period chilling. It is therefore important to select the warmest locations, and also to breed cultivars with greater cold resistance.