What is all the fuss about Nectar?

Look out! The bees must bee swarming!

The apiary was a mass of flying bees from all colonies. What is going on?

Rather than panic lets just sit down and watch what is going on. Always a good plan before doing something rash. The first thing I notice is the intensely strong smell of heather, the bees are collecting nectar and pollen from heather. This is a ‘honey flow’.

With strong colonies the bees are streaming out of the hive in great numbers winging their way to the lower slopes of the Black Mountains about a mile and a half to two miles away.

The excitement of the bees is intense and I have my veil on as bees returning to the colonies are crashing into me and I could easily get stung by a tired over laden bee. I sit down on an old canvas chair and watch the activity in full flow.

There is something highly therapeutic about watching bees at work and this situation is the best to watch.

After a few minutes I notice that one colony is less busy than the others. I watch for a while longer and it is a little lethargic, but nothing to show that anything might otherwise be wrong. I wonder if they have run out of space? I wander over and heft the back of the hive….very heavy, my guess is that they might benefit from another super. It is an interesting scenario as my experience is that with a flow like this the bees will fill every last space in all boxes. Later I put an empty super on this colony and as the flow was continuing the following day the bees also became frantic collecting nectar. This particular flow lasted from 11th to 18th August, a good year for heather.

One of the many factors that intrigued me when I started beekeeping was what plants the bees would feed on and where the honey they made came from. My interest in the local fauna took a sudden step upwards now that I had a vested interest. I read a book called Plants for Bees by Kirk and Howe and then made a chart to show the plants that the bees might be collecting nectar and pollen from.

Plants for Honey Bees – Chris Cardew October 2013 – Sheet1

What is very quickly apparent is that there are main providers of nectar and there are secondary providers. The main sources being mainly native trees in Spring, and then wild flowers, mainly weeds in the summer and autumn with heather in august and then ivy as the autumn turns to winter. The exceptions being Sycamore in Spring and Himalayan Balsam in summer and autumn both being non native. My observations are local to where I keep bees which is rural farmland mainly sheep and cattle, but with the occasional oil seed rape. I also observed that pollen providers outnumber those of nectar with several wind pollinators being a useful source early in the year.

As the seasons passed I found that some were better than others usually with reasons relating to weather, sometimes to my own beekeeping in the early days, with the main issue being not getting colonies built up strongly enough early on in the season.

As my husbandry grew and improved I could look more closely at the ‘honeyflows’ and when they might occur which has led me to want to know more about nectar.

Nectar is one of the four main things that honeybees gather, providing them with the carbohydrates to provide their energy complimenting the pollen that gives them protein.

In Wales where I live and keep bees, the season can be somewhat erratic and this raises many questions among them being the story of nectar; its providers, secretion, abundance and timing.

Of great interest was the biology of nectar and the following paragraphs are taken from ‘Pollination and Floral Ecology by Pat Willmer, Princeton University Press 2011′:

Flowering plants have evolved to work closely or manipulate certain pollinators offering a reward of nectar (and pollen by producing far more than is needed) in order to survive. The plant needs to have certain conditions such as plenty of water, light and warm temperature. Nectar is produced from starch either in storage or by more immediate photosynthesis.

Pollinators have evolved to collect nectar in different ways; insects collect it using their tongue or mouth parts in the case of some flies. Honeybees have a shortish tongue compared to butterflies and some bumblebees which restricts the flowers that they can collect nectar from. However a shorter tongue allows them to collect nectar of a higher concentration 45-60%.

Floral plants secrete nectar from nectaries which can be on almost any part of the flower depending on the flower; petal, sepal, stamen, ovary. They have often evolved together with a pollinator or group of pollinators.

In an evolutionary sense nectar is the secondary main floral reward after pollen, appearing later than pollen in the late Cretaceous period in angiosperms (seed producing plants with flowers).
It has since become the primary offering of a flower in many cases, in so doing protecting the plants investment in the reproductively useful pollen. Nectar is easy for plants to produce and easy for animals to handle, its sugars being simple to metabolize and to use as a readily available fuel.

Nectar is not necessarily associated with flowers, since it occurs in ferns, where it attracts honeybees, and can commonly be secreted extraflorally on the leaves, petioles, and stems of a substantial proportion of terrestrial plants. Thus nectar as a sweet sugary solution from a plant must have existed before angiosperms evolved..

So modern flowers have just taken over nectar production for a more specific function that enhances their reproductive success.

A flower requires a substantial amount of water input as it grows and expands its large surfaces, which would leave an excess of sugars from the phloem (the vascular tissue in plants which conducts sugars and other metabolic products downwards from the leaves.) that could simply be excreted into the flower base to form the beginning of a nectary (a nectar-secreting glandular organ in a flower (floral) or on a leaf or stem (extrafloral)).

Alternatively, a simpler ‘leaky phloem’ model may exist.

Floral nectar is produced by nectaries, which tend to appear as yellowish green surfaces in a flower and are often shining or glistening, sometimes visible nectar droplets on their surface.

A nectary can be positioned wherever appropriate in terms of manipulating a visitors position. (Sepal, Petal, Staminal, Gynoecial) see the drawings below:

nectaries1

ivy-flower img_4900

img_4937

A diagram showing nectar granules on the ovary of the ivy flower. A photo of an ivy flower with nectar granules and then a bee collecting nectar from the ivy flower.

In many plants their cells contain starch granules, which are broken down as nectar is secreted; but in other cases the supply of carbohydrate for the nectar comes directly from photosynthesis via the phloem, and starch is absent.

There seem to be no systematic patterns determining which mode occurs in a given plant, and sometimes both may be present; any plant secreting nectar by night, or before the plants are in leaf, must be using stored starch reserves, but could use a photosynthetic source by day or later in the season. The only clear pattern is that where secretion is fast and copious, stored starch granules are involved and nectary tissue tends to be substantial.

Secretion and exudation of nectar normally continue for a few hours, but can persist for as long as a few days. But environmental effects can complicate the picture. Temperature and light intensity are bound to affect nectar production, since they affect the photosynthetic rate, which in turn will translate into stored starch. Nectar production may decrease at both very low and very high temperatures, and the limits will be set differently for different plants and in different habitats. Water availability is also critical, and plants tend to produce their highest nectar crop after a good rainfall.

The common range of nectar concentration C encountered in temperate flowers is 20% – 50%, rising toward 70% in warm conditions on sunny days.

Animals with longer tongues cannot drink more concentrated nectars. This arises primarily as a consequence of viscosity effects, a concentrated sugar solution becomes too sticky and viscous to rise up or be sucked up a long thin tube. The effect in not linear, since viscosity rise exponentially with C, so that a 60% sugar solution is roughly 28 times as viscous as a 20% solution. Concentrated nectars cannot travel as fast up the long hollow tongue of a butterfly or bee, so the rate of gaining food is too low to be profitable. There is therefore an optimum concentration for a given tongue length and type to achieve the best rate for acquiring calories. At low concentrations this rate is limited by the low energy content of the nectar, and at high concentrations, it is limited by viscosity.

Bees vary considerably in tongue length, but very roughly speaking, the longer tongued species may feed better with 30% – 50% nectars and short tongued ones may be able to cope with 45% – 60% solutions.

Not surprisingly, then, there is a reasonably good relationship between flower type and nectar concentration, with lower values of C in the long tubular flowers preferred by long tongues insects, and more concentrated nectars in the open flowers with exposed nectaries that are more visited by flies and short tongued bees.

Anthophora bees could distinguish between individual Cerinthe flowers on the basis of their nectar secretion rate, perhaps using flower age as a cue, and some flowers do signal their age and altered reward status rather clearly by such cues as colour change. Direct assessment may also be possible, either where a particular nectar is strongly scented so that its abundance could be assessed at some distance from the flower, or where the corolla tube is relatively transparent and the nectar meniscus can be detected visually; there is some indication of this occurring in honeybees.

Each plant therefore does have reasonable scope to get exactly the ‘right’ nectar reward in its flowers at a given time to pay off its visitors and still encourage movement of those visitors onward to other similar flowers. Thus flowers can manipulate animal behaviour quite precisely in space and time to get the best possible pollen movement out of one flower and into another, and so can use their nectar to exert control over their own reproductive success and the gene flow within their population.

…………………………………………………………………………………………………………………………………………………

From observations over recent seasons the ‘nectar flow’ in mid Wales at least is not continuous by any means. If the conditions are favourable we can expect that the spring is the season when the trees provide much of the nectar and the pollen; willow, hazel, blackthorn, hawthorn, fruit trees, sycamore, oak. Some of these being wind pollinated and I include oak as this was a recent finding by the scientists at the Botanical Gardens of Wales who found oak pollen in every jar of honey from samples taken across Wales; in fact the only pollen type to be found in all samples.

The trees that might be a supply of nectar; willow, apple, pear, cherry, sycamore, horse chestnut. This can provide the bees with a good supply up until the end of May.

From June onwards there can be a dearth of nectar and in 2016 June was also wet and cold which meant that the bees consumed a lot of what they had gathered to the end of May. The bramble was in flower but wasn’t providing that much and there were reports that it had dried up in some western counties. From July onwards the nectar flow was moderate as the wild flowers, willow-herb and bramble continued to flower; with the lime tree secreting in some regions and Himalayan Balsam providing a continuous flow from August to October. August 11th to 18th my bees fed on heather and then from mid September to mid October the ivy was very productive. In summary though the 2016 season was a poor one for many because June was so poor. Any beekeeper taking spring honey must surely have had to feed the bees throughout June. There are of course many secondary providers of nectar and pollen, but none that create a visible ‘flow’ like the plants listed above. See the chart above.

Beekeeping can be an enigma and is an activity that allows for continuous learning by doing. When daylight and work commitments allow I will spend at least 10 minutes a day sitting in one of my apiaries watching the activity of the hives on top of anything I may do with hive and colony manipulation throughout the seasons. By doing this one thing that becomes obvious is when the bees are on a nectar flow and for how long this might last. The most recent being when ivy came into flower and started to secrete nectar. There are many interesting things with ivy as with any major nectar provider

An extreme example of crystallization of honey was given by Greenway et al. (1975) who observed that honey largely composed of ivy nectar contained 70% glucose, whereas the average concentration of glucose in honey is only 40-50%. Because of its high glucose content, they ivy honey granulated quickly and then lost water by evaporation, unlike ordinary honey, which is hygroscopic even when granulated, because of its high fructose content. (p114 Honey Bee Pathology Bailey, Ball)

This highlights the issue that some, mostly experienced beekeepers have with the bees filling up their stores with Ivy nectar. Being 70% glucose it granulates to become very hard immediately and is then almost impossible for the bees to re-hydrate. My experience is that when mixed with other nectars the bees cope. However, have a look at my video of the ivy honey flow below compared to the heather honey flow. There are so many more bees with ivy as its so close to the hive compared to the heather being two miles or so away.

So….what do you learn by observation…and …what is the fuss about nectar?

Heather Honey Flow 11th to 18th August 2016

Ivy Honey flow October 2016 (Make sure you listen to the noise!)

Insects feeding on Ivy nectar

 

 

 

One thought on “What is all the fuss about Nectar?

  1. Yes a similar experience with my own bees at my home apiary at 750 feet facing south in the Wye valley. The ivy has provided much winter stores, mixed with proprietary syrup since feeding commenced at the end of September – which gets around the granulation problem and saves on syrup.

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