Fruit colour and size

January 2009 | Prepared by Marcel Veens, horticultural adviser | Future Orchards® notes and presentation

Marcel Veens explains the physiological and orchard-management factors that determine apple colour and fruit size. For red-skinned apples, anthocyanin development is genetically determined but strongly affected by environment and management, particularly light, temperature and the supply of sugars to the fruit.

The notes describe how chlorophyll, carotenoids and anthocyanins contribute to skin colour, and why sunny days combined with cool nights can favour red colour development. Light exposure is especially important for anthocyanin synthesis, while excessive nitrogen can work against colour development. Adequate leaf area per fruit is also important because carbohydrate supply underpins both colour and overall fruit quality.

From a practical orchard perspective, the resource reinforces the need to manage canopy density, crop load and nutrition so fruit receives enough light and assimilate supply. These factors interact with seasonal temperature and variety genetics, which is why colour performance can vary considerably between blocks and seasons.

The accompanying presentation and notes provide useful background for growers making pruning, thinning, nutrition and pre-harvest decisions aimed at producing fruit that meets market colour and size specifications.