Introduction to the Phenological Stages of Citrus

Fournier, in 1978, defined phenology as the study of biological phenomena adapted to a certain periodic rhythm such as budding, fruit ripening and others. These phenomena are related to the climate of the locality in which they occur; and vice versa, from phenology one can obtain sequences relating to the climate and especially to the microclimate when neither one nor the other is properly known.

The events commonly observed in agricultural and horticultural crops are: sowing, germination, emergence (start), flowering (first, full and last) and harvest. Additional events observed in certain specific crops include: presence of buds, leaf appearance, fruit ripening and leaf fall for various fruit trees.

The period between two distinct phases is called a Phenological Stage. The designation of different significant phenological stages varies with the type of plant under observation.

DOMINANT STAGES - CITRUS

• Bud in dormancy
• Swollen bud
• Appearance of buttons
• Corolla visible
• Stamens visible
• Open flower
• Petal fall
• Fruit set
• Calyx closure
• Fruit at 40% development
• Veraison (colour change)