Bee-lines: Series 3 Number 1 - Bees in the trees

I am writing this on the International Day of Forests.

Trees have always fascinated me. Their variety of form, their longevity, the way in which they give shape to our landscapes, particularly in the East of England where hills are modest, mountains are absent and throughout the year it is the trees that mark the season particularly in spring and autumn.

Trees have shaped our architecture, provided materials for much of our furniture and timber is often the ‘canvas’ for decorative carving.

Latterly we have become aware of the symbiosis between trees and mycorrhizal fungi, the complex underground network that physically connects trees with their offspring and their peers – and even between species. The role of trees in creating and supporting biodiversity is breathtaking. They do have a finite life span and need our care and attention.

While contemplating trees and watching my bees out and about in the spring weather I wondered if I could add anything to the familiar truth that honeybees, are by nature, forest creatures albeit that few if any wild colonies of tree dwelling honeybees exist except in a fleeting way in the UK.

Despite the fact that humans have decided to husband honeybees in various styles of box, honeybees have maintained their connections with trees. Much is said, researched and written about honeybees and flowering plants and their interdependence. The pleasure of seeing and hearing our bees together with their bumblebee and solitary bee cousins foraging in our garden borders, vegetable garden and in the wildflowers in the countryside (if you can find any) signifies summer, continuity, bounty – all is right with the world. Because all of this activity occurs close to eye level and in places that we commonly visit it is easy to overlook, undervalue or neglect our bees in the trees.

BBKA have an interesting reminder on their website of the value of trees to honeybees. It can be found in their leaflet Trees useful to Bees.

Do take a look at the BBKA leaflet. The range of useful trees may surprise you or at least remind you.

Also it reminds us that the availability of pollen is every bit as important to the honeybee colony as is nectar. We can perhaps be forgiven for thinking primarily about nectar sources because we like to have a honey crop each summer. Pollen is often gathered by bees as a by-product when foraging for nectar, after all this is the picture we often have in our minds when thinking about the pollination process. In the case of flowering plants that is a common mechanism, and of course plant evolution has favoured flowering plants that can attract pollinators and position their pollen so that it attaches itself to the nectar gatherers. Nevertheless, there are occasions when honeybees forage specifically for pollen particularly at peak brood rearing times.

Bees out foraging specifically for pollen can gather from those plants whose normal reproductive mechanism is wind pollination. Many trees fall into this category and studies have shown that honeybees will gather pollen from hazel, birch, elm, beech and oak.

We are familiar with the spring blossom on almond, apple, pear, and cherry trees. As trees go these are modest in stature but economically important. Their modest stature, although grander than the average border flower is within our unaided eyesight, so we may have some awareness of bees foraging in the fruit trees. Crops later in the year remind us about what happened in the spring. Of course, pollination of orchards is of enormous interest and importance to commercial fruit growers. There are other aspects of the relationship between bees and trees that are critical to biodiversity not least the survival of our honeybees. Close by where I live there are many lime trees; several hundred within a mile or so. When the limes are in flower albeit briefly and the sun is shining the interest shown by bees is intense. Standing beneath a flowering lime tree listening to the exuberant buzzing of honeybees and bumblebees is one of summer’s many treats, but all too short lived.

A feature of the ecology of lime trees and many others including beech and oak are aphids, often tree species specific. And the presence of aphids means honeydew; the excess sugary liquid that these sap suckers release from the leaves of their target. I doubt that any of us have apiaries that are not within bee flying distance of a lime, oak or beech tree.

Another common feature of trees, certainly where I live is ivy. Ivy will try its luck on almost any near vertical surface that it comes across as it moves from being a ground dweller to a climber. It doesn’t matter if the tree (or hedge for that matter) is coniferous or deciduous, native or introduced. Give the ivy half a chance and it is away, skyward. Close by my apiary are larch, pine, struggling elm, sycamore and more with their overcoat of ivy. Efforts have been made recently to benefit the host trees by cutting the ivy stems, some 5cms in diameter to kill the ivy. I have mixed feelings about this. For the sake of the trees wellbeing and aesthetics, killing the ivy is unquestionably a good thing – but as a beekeeper I can see a couple of negatives. I won’t attempt to discuss the merits of ivy as a habitat for birds and insects. If I did then I think I might relent and come down in favour of the ivy. Anyway the ivy is dying so how will that impact my bees. The loss of the ivy as a rich food source for my autumn foraging bees will have an impact as there were days in October and November when the bees were beside themselves with excited flights of no more than 10 metres from hive to ivy cloaked larch and pine returning laden with nectar and covered in ivy pollen. I will observe with interest this autumn but feel certain that there remains sufficient unmanaged ivy in parts of the adjacent woodland for inquisitive bees to find.

Last year my bees produced swarms. All bar one was gathered up. The fate of the escapees is unknown but they certainly headed for the trees. My most exciting and educative swarm performed as follows. It left its hive and made for a nearby ornamental pear tree. It gathered and hung there for only a few minutes – no chance to collect it. Then off it went up into one of those ivy covered pines, disappeared into the dense green blanket about 15 metres above the ground. No chance of gathering it now. But, last year was the first time (foolish me for not listening to others sooner) that I set up a bait hive. The bait was set, still in my garden but away from my hives and only about 25 metres from where the swarm seemed to enter the ivy blanket. Within an hour or two the first bees had found the bait hive and were going inside, appraising the box and its contents. It was like having a house open for viewing ahead of an auction. The number of visitors to the bait steadily increased and they stayed longer to look around inside. This continued until around 2pm on the next day there was a steady stream of potential buyers. Then joy of joys I stood by the bait hive as the swarm that had overnighted in the ivy covered tree took flight and purposefully streamed into the bait hive and took up home. I must say thank you pine tree and ivy. That was the easiest and most delightful swarm collection that I have so far experienced.

And finally in this homage to trees, detailed analyses show that the chemical composition of propolis varies considerably from region to region, along with the vegetation. In northern temperate climates, for example, bees collect resins from trees, such as poplars and conifers. Sometimes we may curse propolis but at the same time marvelling at its origin, properties and purpose.

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