Growth of orange shoots

Abstract

Growth of orange shoots in the Mildura area occurs in three flushes, initiated in July, December, and February. Most important is the July (spring) flush, which produces many more shoots than the later flushes combined and also sets the orange crop. Spring shoot growth is concluded about the end of September but leaf growth and flower development continue until the end of October. Spring leaves are smaller than those of later flushes. Leaves on flower shoots are smaller than those on vegetative growth. Spring shoots may be divided into five morphological classes, ranging from flowers with no leaves to vegetative shoots (Fig. 1). Leafy inflorescences set more fruit than leafless inflorescences and produce more new shoots. The stalks of leafless inflorescences generally do not persist for more than a few months. Most new shoots arise in near-terminal leaf axils on vegetative growth of the preceding spring or summer. Vegetative shoots tend to produce more flowering shoots than inflorescences do. Proportionately fewer flowering shoots are produced by fruiting shoots than by inflorescences which do not set fruit. The tendency of a shoot to produce new floral or vegetative shoots is apparently modified by the nature of the current shoot population. The ability of a particular shoot to produce a fruitful inflorescence is not affected by the nature of the shoot on which it arises.