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Weather and blueberry quality – how do heat and rain affect fruit during harvest

Weather and blueberry quality – how do heat and rain affect fruit during harvest?

High temperatures, heavy rainfall and high humidity can change blueberry quality in a short time. Find out how to organize harvesting and fruit handling under changing weather conditions.

Weather during harvest directly affects blueberry quality

During the harvest season, blueberry quality can change very quickly. A batch picked in the morning after a cool night may behave differently from fruit of the same variety harvested several hours later during hot weather. Rainfall can likewise change harvesting conditions almost from one day to the next.

Temperature, sunlight, water availability and fruit moisture affect not only the plantation itself, but also the subsequent shelf life of the harvested product. For this reason, following a rigid schedule during harvest is not always sufficient. Work organization should be adjusted to current weather conditions and the actual condition of the fruit.

This is particularly important for blueberries intended for the fresh market, where firmness, appearance and storage potential affect the commercial value of the batch. We discuss the differences between various fruit destinations in the article dessert, fresh-market and processing blueberries – how do sorting requirements differ.

What happens to blueberries during hot weather?

High temperatures accelerate processes taking place both in the plant and in harvested fruit. After picking, blueberries continue to respire and gradually lose water. The higher the fruit temperature, the faster the processes associated with loss of freshness may occur.

The problem does not begin only in the cold store. Fruit can already heat up on the bushes and later also in containers left on the plantation. If full containers remain in direct sunlight for a long time, fruit can reach the cold store at a much higher temperature than when it is collected efficiently from the field.

For this reason, during hot weather the time between picking the fruit and moving it to a cooler location becomes particularly important. The more efficiently fruit is collected from the plantation, the easier it is to limit unnecessary heating of the harvested batch.

Why does high temperature reduce the time available after harvest?

From the point of view of post-harvest quality, temperature is extremely important. As temperature increases, the respiration rate of the fruit also rises, which means faster consumption of stored resources and acceleration of ageing processes.

In practice, this means that during hot days the farm has less time to efficiently collect, cool and prepare the fruit for the next stage. A work organization system that is sufficient at moderate temperatures may prove too slow during a heatwave.

Water loss is also one of the factors associated with later loss of firmness. We describe this mechanism in more detail in the article why blueberries soften after harvest.

Is it worth changing harvest hours during hot weather?

If farm organization allows it, part of the harvest can be moved to cooler hours of the day. This does not mean setting one universal harvesting time for every plantation, but rather limiting situations in which fruit is harvested and then left in the field for a long time during the strongest sunlight and highest temperatures.

In practice, it is worth monitoring not only air temperature, but also how quickly the fruit itself heats up and how long it takes to collect full containers from different parts of the plantation.

If working hours cannot be changed, good logistics becomes even more important. Full containers should be collected regularly, and harvested fruit should not remain unnecessarily in a sunny location.

Hot weather places greater demands on irrigation

High temperatures also increase the importance of proper plantation irrigation. During hot and dry periods, the plant must simultaneously maintain its green parts and developing fruit.

For this reason, before and during periods of high temperature it is worth checking the irrigation system particularly carefully, together with actual water availability in different parts of the plantation. A fixed irrigation schedule does not always match the current needs of the plants.

This does not mean that the solution is simply to maximize the amount of water applied. Irrigation should be adapted to soil conditions, weather and the actual needs of the plants.

How does rain affect blueberries during harvest?

Rain during ripening and harvesting creates a completely different set of problems than hot weather. The most obvious change is the presence of water on the fruit surface, but heavy rainfall can also increase the risk of damage and cracking in some fruit.

Not every variety and not every batch reacts to rainfall in the same way. Ripeness, weather conditions before the rain, rainfall intensity and fruit condition all matter. After heavy rainfall, it is therefore worth assessing the fruit more carefully before beginning the next harvest.

If the proportion of cracked, damaged or very ripe fruit has clearly increased, the batch may require a different approach during later preparation and sorting.

Why is it better to avoid harvesting wet fruit?

Whenever possible, it is advisable to avoid harvesting fruit that is wet from rain, dew or fog. Water remaining on the surface of blueberries creates less favorable storage conditions and may increase the risk of later quality problems.

This does not mean, of course, that harvesting can always be stopped for many hours after every rainfall event. At the peak of the season, the decision must also take into account the amount of ripe fruit and the weather forecast for the following days. However, if it is possible to wait until the fruit surface has dried, this is preferable to harvesting fruit while it is still completely wet.

During prolonged rainy periods, more frequent plantation inspections may be necessary. Leaving very ripe fruit on the bushes while waiting for several perfectly dry days can also result in quality losses.

Rain can increase the risk of fruit cracking

One of the problems observed after rainfall before harvest is fruit cracking. A crack in the skin is not only a visual defect. Damaged fruit loses its commercial value more quickly and becomes a much greater problem during storage and transport.

After heavy rainfall, it is therefore worth looking not only at the amount of fruit ready for harvesting, but also at the proportion of berries with cracks and other damage. This makes it possible to decide earlier how a particular batch should be handled.

If fruit quality becomes more variable after a weather change, later sorting should take into account the actual condition of the specific batch rather than relying only on settings used several days earlier.

Check quality more frequently after rain

After a period of heavy rainfall, it is worth increasing the frequency of fruit quality checks. This applies both to assessment on the plantation and to inspection of the first harvested containers.

It is worth paying attention to:

  • fruit firmness,
  • the presence of cracks,
  • the proportion of overripe and damaged fruit,
  • moisture on the fruit surface,
  • quality differences between different parts of the plantation.

If you want a more repeatable assessment than simply checking the fruit by hand, you can find more information in the article how to check blueberry firmness.

A change in weather can mean a change in the quality of subsequent batches

One common mistake is to assume that fruit of the same variety will behave in the same way throughout the entire season. In reality, consecutive batches from the same plantation block can differ significantly in quality because their condition is influenced by the weather conditions during the period preceding harvest.

Firmness, the proportion of damaged fruit, the level of ripeness and post-harvest shelf life can all change. For this reason, subsequent batches should be treated as products requiring ongoing assessment, particularly after sudden changes in weather.

This also applies to later classification. If the characteristics of the fruit have changed, the process parameters may need to be adjusted. We separately explain how to set quality thresholds in a blueberry sorter and how to adjust blueberry sorter settings for different varieties.

During hot weather, efficient collection and cooling are most important

On hot days, transport organization from the plantation becomes particularly important. Even properly harvested fruit can heat up quickly if it remains in full containers in direct sunlight for a long time.

It is therefore worth shortening the time between harvesting, collection from the field and the start of cooling. On larger farms, this may require more frequent collection of containers or a change in internal transport organization during the hottest hours of the day.

Proper post-harvest handling has a direct impact on later product shelf life. We discuss this topic in more detail in the guide how to extend the shelf life of blueberries after harvest.

Weather also affects sorting operations

Changes in fruit quality caused by weather are also visible later, when the product reaches sorting and packing. After several hot days, the proportion of fruit with reduced firmness may increase, while after heavy rainfall there may be more damaged, wet or cracked berries.

For this reason, the first containers harvested after a significant change in weather conditions should be treated as a sample of the entire batch and checked carefully. If their characteristics differ significantly from the previous delivery, the following process should be adjusted accordingly.

Before feeding the product onto the line, it is also worth ensuring that it is properly prepared. We describe this in detail in the article how to prepare blueberries for sorting.

For farms using automatic classification, a properly selected blueberry sorter makes it possible to separate fruit according to defined quality criteria, but the basis remains proper assessment of the current batch and adjustment of the process to its actual characteristics.

How should you respond during hot weather?

During periods of high temperature, it is particularly worth:

  • regularly checking the condition of fruit on the plantation,
  • checking the operation of the irrigation system,
  • organizing harvesting during cooler hours whenever possible,
  • avoiding leaving full containers unnecessarily in direct sunlight,
  • increasing the frequency of fruit collection from the plantation,
  • moving harvested fruit to the next stage and cooling as quickly as possible.

How should you respond after heavy rainfall?

After rain, it is worth:

  • assessing fruit condition before resuming full harvesting,
  • waiting for wet fruit to dry whenever possible,
  • checking the proportion of cracked and damaged fruit,
  • checking firmness and general batch condition more frequently,
  • separating batches that clearly differ in quality,
  • reassessing sorting parameters and how the fruit should be handled.

There is no single harvest schedule for every type of weather

The key conclusion is that harvest organization should not be completely separated from weather conditions. A fixed plan may work for much of the season, but during a heatwave or several days of heavy rainfall it may need to be adjusted.

Sometimes this may mean starting work earlier, collecting fruit more frequently or cooling it more quickly. In other cases, it may mean delaying the harvest of wet fruit for several hours, increasing quality checks or changing how a particular batch is prepared.

The faster the farm responds to changing conditions, the easier it is to reduce situations in which problems originating on the plantation become visible only during packing, storage or transport to the customer.

Summary

Heat and rain affect blueberries in different ways, but in both cases a quick response from the farm is essential. At high temperatures, the main priorities are limiting the heating of harvested fruit, efficient transport and cooling as quickly as possible. After rainfall, greater attention should be paid to moisture, cracking, damage and the general condition of the batch.

Not every change in weather results in a loss of quality, but sudden conditions can cause one batch to differ significantly from the previous one. During harvest, it is therefore worth regularly observing the fruit and adapting work organization to its actual condition instead of assuming that one established procedure will remain suitable throughout the season.

After harvest, the next important stage is limiting further quality loss and properly preparing the fruit for cooling, sorting and packing. More practical information can be found in the guides how to extend the shelf life of blueberries after harvest and how to prepare blueberries for sorting.