Fall 2014: End of season in the greenhouse - what to do?

Lower light levels and shorter days require adjustments to the climate and water strategies used for the last few months of the crop. Most crops are approaching the topping stage - end of September topping for an end November/early December final harvest and cleanup.

The plant's requirement for water and nutrients, in general, decreases with the lower light and shorter days, and no new growth occurs (after topping there is new growth is restricted to sucker growth which should be minimized or removed). All that is needed is the maintenance required for the leaves and fruit size increase. However, fruit quality and insect and disease management are still key concerns.

Improved fruit quality and disease management can be attained by ensuring that the greenhouse is set to increase transpiration, prevent free water on the plants, maximize light transmitted (greenhouse coverings cleaned to remove any applied shading compounds), and that the proper fertigation (amount of water, when to start and stop, EC to apply, etc.) practices are applied.

Fruit quality is developed in the growing area and once harvested, the fruit quality decreases. Thus it is optimal to have the ideal conditions in the greenhouse to attain the highest fruit quality:

  • Ideal temperature - high fruit temperature will not allow fruit colour to develop properly (green or discoloured spots on the fruit) or too low a temperature will not allow full colour development.
  • Excess water applied to the crop will increase the chances of fruit splitting or soft spots on fruit. Low EC feed will result in excess water taken up by the plant.
  • Poor climate management resulting in stagnant humid conditions will increase the chances of disease infection (botrytis, late blight etc.) and fruit surface pathogens that may decrease shelf life.

The rate of decrease in quality is altered by the temperature maintained in the post-harvest area, the nutrient quality of the fruit (i.e. the fruit had all the nutrients supplied to it, e.g. calcium deficiency due to too rapid a fruit expansion) and nutrients available to the plant.

Recommended temperature conditions for post-harvest handling of greenhouse vegetables are 12- 15C to maintain shelf-life and flavour. It is important to maintain a steady temperature once the produce is harvested as fluctuating temperatures (moving back and forth between cold storage to room temperature) will allow free water to be present on the fruit increasing disease infection.

Figure 1: Poor climate conditions in the greenhouse lead to post harvest fruit quality issues.

Figure 1: Poor climate conditions in the greenhouse lead to post harvest fruit quality issues.

Figure 2: Correct climatic conditions are needed to maintain the high quality of these harvested vegetables.

Figure 2: Correct climatic conditions are needed to maintain the high quality of these harvested vegetables.

Figure 3: Post-harvest fungus growing on fruit stem of pepper

Figure 3: Post-harvest fungus growing on fruit stem of pepper

Figure 4: Post-harvest rot in cucumber.

Figure 4: Post-harvest rot in cucumber.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca