Clarity about Plant load, Assimilate and Plant balance in ornamental crops

Published on
March 2, 2023

An optimal greenhouse climate enables ornamental growers to get the most out of their crop. They can control properties such as Plant load, Assimilate and Plant balance. In discussions with fellow growers and advisers, it is important that everyone has the same understanding of these terms. In the study 'Measuring and controlling plant load in ornamental horticultural crops', definitions and a plant physiological interpretation of those terms for ornamental horticultural crops have been drawn up.

The Plant load, Assimilate and Plant balance each play their own role in the growth of an ornamental plant. As an illustration: by adjusting the plant load (the total sink/m2 of greenhouse/week) to the expected light sum during the growth of the cut flower or pot plant, more can be grown with natural light. In this way, a grower can save on heat and electricity.

On lighter days, the greenhouse temperature can be increased to make optimal use of the sunlight for the production and processing of assimilates, the products of photosynthesis, such as sugars and starch. The assimilate balance plays a role in this: the relationship between supply and demand of assimilates. The plant balance is the balance in production and growth of harvestable and non-harvestable plant parts, so that the plant can grow and deliver the product quality in the way the grower wants.

As part of Het Nieuwe Telen, the definitions and effects of these terms are often applied in vegetable crops, but much less so in ornamental crops. The terms for ornamental plant crops have now also been described. This has been elaborated in cultivation instructions for four crops: rose, chrysanthemum, freesia and gerbera.

The study 'Measuring and controlling plant load in ornamental plant crops' was financed by the Kas Als Energiebron programme.