Understanding blossom and nectar flow is an essential need for every beekeeper – or rather trying to understand them, as the subject can become very complex. Over the years, professional beekeepers develop this critical know-how for their operations. Backyard beekeepers start with a few basics and try to refine their perception through more or less in-depth observation.

Keeping track of the blooms

One aspect that makes beekeeping an interesting practice is that it immerses you into nature. You become an informed observer of the ecosystem because you and your bees depend on it.

There are multiple resources available online dealing with blossoms. Two good examples are the bee forage regions from NASA HoneyBeeNet network in north America or the ApiBotanica repository from INRA in France.

At the end of the first beekeeping season you easily assimilate the blossom calendar: in March cherry trees, in April apple trees and rapeseed. May is for Robinia and June for Chestnut and Lime tree. Then in August it's the dearth …

This careful monitoring of the natural environment allows you to perceive events that go unnoticed to the uninitiated. But keeping track of the blooms does not mean understanding the nectar flows...

Flowers are a necessary but not sufficient condition for nectar flow

Having flowers does not necessarily imply the existence of nectar or resources for bees. The nectar flow depends on many factors: the ambient temperature and humidity, the last rains and their intensity, the depth of the roots for plants such as rapeseed or sunflower...

The nectar flow is neither acquired nor easy to identify. Especially since you will not stand guard under your neighbor’s apple tree to check if bees come foraging!

Measuring weight variation to understand nectar flow

A connected hive with a weight scale will give you much more detailed information about the colony behavior. At a glance it becomes possible to follow the nectar flows, their intensity and also the periods of dearth.

These graphs display the raw weight of the hive. They integrate the different feedings, additions & removals of hive elements. Moreover, it is not always easy to know precisely the gained or lost weight during the day, due to the colony's own dynamics with bees that go out in the morning, come back in the evening, dehydrate at night...

Within BroodMinder we have developed the Nectar Flow Calendar to separate the bees' work from everything else. This tool allows to follow the productivity of each colony equipped with a scale. Weight variations are monitored on a daily basis, removing effects not associated with the bees to restore the net daily production.

Nectar flow Calendar

With daily information available, it is no longer a simple "onset-and-closing of bloom" that is monitored. Actually, information is much richer. It is a daily follow-up of the nectar flow progress and intensity with its ups and downs.

Colony weight gains and losses displays clearly the nectar flow calendar (it can also be "pollen flow"). Green circles are for weight gain, red circles for weight loss. Their size represents the amount gained or lost each day.

Beyond the funny aspect of this data visualization, it is a real decision support tool. It enables you to determine the right moment to install a new supper or, on the contrary, to support a colony lacking of reserves.

Precision beekeeping is transforming the practice of apiculture. Accurate nectar flows assessment is an asset for every beekeeper. From this perspective, a better understanding gets you closer to the environment for a more precise, more intense practice.

Now, that theory is exposed, let's analyze a practical case. This is the case for Blooming and nectar flow of linden tree this last summer.

Understanding blossom and nectar flow for linden & chestnut.

In my apiary in the french Pyrenees, this year the chestnut tree nectar flow joined the lime tree one. I saw early chestnut trees bloom before the linden tree, as well as late chestnut trees finishing afterwards. It's not easy to sort out which one has honeyed and when!

Start of bloom End of bloom
Early chestnut tree May 20th June 14th
Linden tree June 9th June 28th
Late chestnut tree June 10th July 5th
Observed dates of onset and end of bloom

The period of total bloom extends from May 20, until approximately July 5. But in fact, the nectar harvest starts on May 27th and ends on July 2nd. The productivity calendar, here below, also shows that not every day weights the same in this period. The second half of June produced the vast majority of the harvest (hover over the graph with the mouse to see contextual information).

Gains or losses are related to the blooms, as much as they are related to the weather. When the flowers are available, the weather will condition the continuation. For example, the chestnut nectar flow that took place at the end of May can be associated with a week of good weather. The bees brought in from 0.6 to 1.2kg/day.

The first two weeks of June were more mitigated. Probably because of the recurrent rain (260mm in total) which certainly limited the bees' harvesting flights. However, the rain moistened the soil and prepared the nectar flow that was to follow...

Indeed, the bees recovered production during the following two weeks. With a generally overcast sky and maximum temperatures ranging from 18 to 30°C, the bees worked well every day without exception, bringing into the hive 2.0 to 2.5kg/day.

Zoom on the linden nectar flow

If we look at the graphs, we can say with certainty that the week of June 14 was THE week for the lime tree. I am often asked if the production of one hive is similar to that of its neighbors. Well, it turns out that in this apiary, several hives are equipped with scales, let's see how each colony did over the period:

We see above that all these colonies made a good harvest. However, on this graph the starting weights are not identical, and it is difficult to compare their evolution.

Shifting to the following calendar representation, we can better visualize the nectar flow intensity in each colony:

Nectar flow intensity on 4 hives of the same apiary

Overall, we see an increasing progression in the nectar flow intensity as the week progresses. The weekend of June 20 is the peak in intensity. Nevertheless, important differences are visible between the colonies. Production goes from simple to more than double. Each colony harvested between 4 and 11 kg of nectar this week.

Wrapping it up

Understanding blossom and nectar flow is a major asset in beekeeping. Field observation can advantageously be combined with measurements from connected hives scales. The interpretation of events thus becomes much more concise. Reaching another level of understanding of bee behavior is then possible.

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