“Bee foraging on garden plants: Sussex University research” – a talk by Professor Francis Ratnieks

Yesterday evening I went to a talk on “Bee foraging on garden plants: Sussex University research” by Professor Francis Ratnieks at the Jodrell Lecture Theatre, Kew Gardens. Francis is the Professor of Apiculture (Evolution, Behaviour and Environment) at the University of Surrey – the only Professor of Apiculture we have in the UK!

Before the talk began, a student read some gardening themed poetry for us, which I enjoyed. The poems included ‘Tree at my Window’ by Robert Frost and ‘Come slowly – Eden!’ by Emily Dickinson. Prof. Ratnieks must be a fan of poetry too, as he began his talk by quoting a line by Rudyard Kipling:

There’s a whisper down the field where the year has shot her yield, And the ricks stand gray to the sun, Singing: — “Over then, come over, for the bee has quit the clover, And your English summer’s done.”

He then went on to discussing his research, which has covered many different topics to do with bee health and foraging behaviour over the years. He has done research to try and find out the main pollinators for commercial crops such as apples, pears and blueberries in the UK. One of his studies in East Kent found that 61% of insects visiting pear & apple flowers were honey bees, while a similar May 2012 study of blueberry flowers found 65% of insect visitors were honey bees. This was despite the blueberry farmer having put out hundreds of bought-in bumble bee colonies (Bombus Terrestius) amongst his crops. Pollination is big business now, with US beekeepers paid $175 per pollinating hive for the Californian almond crop.

Honey bees on apple flowers

Honey bees on apple flowers

It may surprise some readers to hear that he considers the two main threats to bees to be diseases and fewer flowers in the countryside/habitat loss/intensive farming – not pesticides, climate change, mobile phones or any of the sensational stories the media likes covering! This correlates with the views of Dr Stuart Roberts, whose talk on the decline of insect pollinators I blogged about last year.

Flower research

We are losing large patches of common flowers such as knapweed and ragwort. These flowers are not going to go extinct, but they are the bread-and-butter of honey bee foraging.

Quite often books suggest that people plant spring flowers, to get colonies going early in the year. Yet Professor Ratnieks has found that the average distance foraged by honey bee colonies he studied in March was 1/2 kilometre. In July, this increased to 2km. The reason for this? In spring, bees find it in easy to find flowers, whereas in summer they have to go further. Despite the warm weather of summer, in terms of planting available forage it is then that bees really need our help, more so than in winter. Don’t bother planting flowers for bees in January – they will only have about one day’s foraging time.

Ragwort - this pretty yellow flower gives the bees both nectar and bright yellow pollen.

Ragwort – this pretty yellow flower gives the bees both nectar and bright yellow pollen.

Ivy flowers in autumn.

Ivy flowers in autumn.

In autumn ivy comes along and acts as an incredibly important late source of forage, providing both nectar and pollen. Professor Ratnieks found that 91% of all pollen collected by his bees during mid-Sept to mid-Oct was ivy pollen. He told us he’d come to the conclusion that “If ivy wasn’t invented already then it probably should be”. And yet its unshowy flowers go unnoticed and unappreciated by many.

The best plants for bees

July and August (in the UK, anyway) is when bees need the most help, so if you want to encourage the animated soft hum of happy bees in your garden, give them summer flowering garden plants.

A study by a Phd student Professor Ratnieks supervised, comparing around 32 common garden plants, found that there was a 100-fold range in attractiveness to insects between the best and worst plants. The worst plant was a red pelagonia, which attracted nothing! The best plants were…

Lavender – especially good for bumble bees
Borage – especially good for honey bees and other insects too
Majoram – attracted a wide variety of insects

Now, you might ask: why do bumbles prefer lavender and honey bees borage? Professor Ratnieks believes that the delicate flowers of borage are more suited in size to little honey bees, rather than big, bouncy bumbles.

Bumble bee landing on borage

Bumble bee landing on borage – it happens occasionally!

As for lavender attracting bumbles more often, this is likely to be because bumbles are faster on the lavender flowers. Bumble bee species tend to have longer tongues than honey bees, which enables them to collect nectar from each lavender flower in a speedy 1.5 seconds. In comparison the shorter tongued honey bees must really stick their tongue out, and end up taking around 3.5 seconds per flower.

Each lavender flower contains a minute amount of nectar, so the extra couple of seconds makes a real difference in foraging efficiency.

Shortening some lavender flowers with cuts reduced the times honey bees spent visiting each flower, thus backing up the theory that it is their shorter tongue slowing them down. In a further experiment with lavender flowers, Professor Ratnieks devised a ‘High-Tech Whacking Stick’. This crucial piece of equipment was a stick wielded by his research students. They used it to selectively deter bees from visiting two different patches of lavender – in one patch bumbles were excluded, while in another honey bees were excluded. A third control patch with no bees excluded was also used.

What the students found was that when bumble bees were excluded, honey bee foragers quickly built up on the lavender. Whereas on the control patch where bumbles were not excluded, there were hardly any honey bees present. It appears to be the case that bumbles deter honey bees from visiting lavender by being quicker than them – there’s almost no point the honey bees trying.

‘Bowles’s Mauve’ wallflower – best for butterflies

A plant for butterfly fans. Butterflies are harder to attract than bees, mostly because there are fewer of them. A British butterfly won’t lay her eggs on a non-native plant, so bear this in mind.

Honey bee on borage. Courtesy The Food and Environment Research Agency (Fera), Crown Copyright.

Honey bee on borage. Courtesy The Food and Environment Research Agency (Fera), Crown Copyright.

Differences between urban and rural honey bee foraging

Oil seed rape is an important UK crop; it will soon be the 2nd biggest arable crop in England. Professor Ratnieks decided to study just how often foraging honey bees around Brighton visited oil seed rape, which is renowned for being attractive to bees. His results were surprising to me – in Brighton most foragers stayed in the city and ignored the oil seed rape fields within their foraging range, while on average the rural colonies surrounding Brighton visited the rape field for about 10-20% of their foraging. This was determined by both studying waggle dances and collecting pollen samples.

Professor Ratnieks had expected the figure for rural colonies visiting oil seed rape to be higher, as these were big fields. If colonies are not choosing to collect the majority of their nectar and pollen from oil-seed rape that is good news, as it will help them avoid the pesticides commonly used on rape crops.

As an aside, Professor Ratnieks commented that he feels the number of hives in central London now is “ridiculous”. Companies have been installing hives on their rooftop to increase their green credentials, without any understanding of the sustainability issues. In his view the whole of central London would need to be converted into fields of borage in order to properly support the hives currently there.

Lots of beekeepers say that towns are better for bees than countryside; he believes it is not so much that towns are good for bees as that the UK countryside is crap! We have turned our countryside into a desert of monocrops.

There is a video about the research available on YouTube, narrated by Professor Ratnieks – Quantifying variation among garden plants in attractiveness to bees and other insects. Thanks to @MerryBeeBo for letting me know about this in her comment on this post.

Oxalic acid research

Prof. Ratnieks noted that the UK National Bee Unit had not done any research comparing the efficiency of oxalic acid treatments by the different methods of vaporisation, spraying and drizzling. He realised that such research would be cheap to carry it out, so set about doing it himself.

The results surprised me – vaporisation was the most effective way of killing varroa using oxalic acid, and also resulted in no bee deaths. Spraying oxalic acid was the most toxic method, though only resulted in a couple of bees per day dying in the week after application. The advice I have seen given in BBKA News before has been that vaporisation  requires too much care in handling to be worth it (the fumes can be toxic to humans), but if it is significantly more effective perhaps our Association should be looking into doing it that way.

About Emily Scott

I am a UK beekeeper living in Ealing, west London. I have been keeping bees in the Ealing Beekeepers Association’s local apiary since 2008 and created this blog as a record for myself of my various beekeeping related disasters and - hopefully - future successes. Busy taking the British Beekeeping Association module exams too!
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39 Responses to “Bee foraging on garden plants: Sussex University research” – a talk by Professor Francis Ratnieks

  1. Great blog Emily! I did notice in my own garden that the borage I planted for honeybees was exclusively fed upon by bumblebees. Did the good professor name other plants that are top choices for honeybees in domestic gardens?

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  2. Alex Jones says:

    I have noticed that ivy tends to be alive with buzzing insects at certain times of the year.

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  3. In relation to Ragwort, did Francis mention the 1959 Weeds Act as amended by the Ragwort Control Act 2003?
    Ivy makes the scrummiest honey (if you like Marmite, you’ll like ivy!). I once heard one customer asking another ‘Did you get the citrus overtones?’

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  4. Barny says:

    Thanks Emily for that summary of what sounds like a most interesting talk. What was the comparison between drizzling oxalic acid against fumigation and spraying?
    In response to Westerwilson’s question; Phacelia is also a good garden flower for bees. When the weather conditions are right they go mad for the pollen from my weeping willow in spring.
    Hope your revison to going well. March 23th is looming!

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    • Emily Heath says:

      Drizzling wasn’t as effective as fumigation in the graph he showed, but I didn’t get time to scribble down the exact numbers. I’ll try to see if the presentation is available from Kew.

      Had to google to find out what Phacelia looks like, don’t think I’ve seen it in gardens locally. It looks like it would be popular with bees, being blue and an open flower.

      Eek, March 23rd is coming up all too soon! Are you taking an exam too?

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  5. This is really interesting research and information Emily, the flower research especially. I did a post on a study by Danforth Labs at Cornell University that had a different outcome on bees visiting commercial fruit crops, like apples in NYS. It suggested that farmers forgo trucked in bees and look to native bees for pollination. You might check it out and see how it is much different than the findings presented at the lecture you attended. You reported, “One of his studies in East Kent found that 61% of insects visiting pear & apple flowers were honey bees, while a similar May 2012 study of blueberry flowers found 65% of insect visitors were honey bees.” I suspect the difference is the bees that are brought to a site as opposed those honeybees that just show up on their own. My post: http://gardenwalkgardentalk.com/2013/01/24/native-pollinators-are-better-so-says-science/
    I am interested what you as a bee expert thinks.

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    • Emily Heath says:

      Thanks for the link. The research by Prof. Ratnieks (from what I remember) involved counting the numbers of bees seen on the trees (I could be wrong on this, I need to get hold of the presentation really). If so, that wouldn’t take into account whether they were collecting pollen or nectar. The article linked to from your post says ‘”An individual visit by a native bee is actually worth far more than an individual visit by a honeybee,”…. “Honeybees are more interested in the nectar. They don’t really want the pollen if they can avoid it. The wild, native bees are mostly pollen collectors. They are collecting the pollen to take back to their nests.”‘ There may be something in that – although honey bees obviously do collect pollen, they are also trying to collect stockpiles of nectar, which native bees are not trying to do.

      Of course in the UK honey bees are native pollinators 🙂

      I attended a talk last year by Dr Stuart Roberts, an entomologist at Reading University – he thought that honey bees only carry out about 9% of pollination on agricultural crops in the UK: https://adventuresinbeeland.com/2012/02/26/bee-keepers-day/. So not even the experts agree!

      Ultimately I think we need to look after all our pollinators, they all have a role to play in helping us. If the almond tree growers allowed native flowers to grow in-between the trees and provided tussocky areas of grass for native bees to nest in, perhaps they wouldn’t have such a need to import in honey bees.

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      • It is true that honeybees are native to Europe so the study refers to all bees over there. I think it is funny how so many experts disagree, especially when they are counting bees. Thanks for looking at Cornell’s research and adding to the discussion. I really is a matter of perspective, but there must be so many factors involved too, like time of year, weather and season. Thanks again.

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  6. Mei says:

    That was a really interesting post. Thank you for sharing. Our bees are fairly lucky in the suburbs of London I think where the majority of householders tend to plant a variety of summer blossoms, not all of them bee friendly I admit but a good few sure are.

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  7. Karin Alton says:

    Hi Emily The number of garden plants that our PhD student compared was 32, not 300! Best Karin

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  8. I know that when my sedum ‘Matrona’ is blooming in the fall, it’s absolutely crawling with bees — honey and bumble both, being a sturdy flower — and little skipper butterflies. It’s probably the thing I look forward to most about my garden.

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  9. solarbeez says:

    Speaking of sedum, after we found out about Autumn Joy, in late September, I asked my wife to buy some. As she was carrying it out to the garden, she had several bees land on it and start working it.
    I never knew we had so much ivy growing around here until you mentioned it in my blog about the bee activity in late November. You’re right, the blossoms don’t look like much, but the bees are all over it.
    Since this is my first winter of having bees, I’m detailing what they feed on mid-winter. So far, I’ve got video of bees on rosemary, acacia, heather, pussy willows, laurel, and GORSE (transplanted from Ireland in 1873).

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    • Emily Heath says:

      Astonishing that bees would land on the sedum before it was even in the ground! What a plant. I’m jealous that you have plants like rosemary and heather flowering in mid-winter, those are summer plants here!

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  10. Wendy says:

    Hello – I was very interested to read this. The research coming out from Sussex University proves that so many of the things we think we know about bees are there to be challenged. And although there doesn’t appear to be enough forage for bees in London, it would be a shame to discourage beekeeping there. I’m sure many more people care about bees now because of these roof top hives – but I don’t know what the answer is to this.
    It was obviously a fascinating lecture!

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  11. Fascinating! It is so good to hear your account of the lecture. Nothing can replace solid research to find out more about honey bees and bumble bees. The research on the rape seed foraging is extremely important and I wonder if this has been repeated elsewhere. Much more needs to be done and repeated locally on foraging patterns instead of guessing. I find it so sad that gardens now offer an important source of forage for bees in the UK. Over here we notice each year more little wild areas are cleared and joined on to the already cultivated areas. It is a slow but steady progression.

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  12. disperser says:

    Interesting reading, as always.

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  13. Pingback: BBKA module 6: honeybee behaviour 6.7 the foraging bee | Miss Apis Mellifera

  14. daveloveless says:

    Going back to the cause of bee decline, I do think a lack of flower variety is at least part of the problem. It’s not a great mono-diet, and that’s why I think urban beekeepers have a great role to play in the long-term survival of the species. I’ve noticed how I almost always do at least a little better in terms of production and survivability than my non-urban counter parts in the immediate region. Not much better, but better.

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  15. Here are a couple of interesting bee-science articles. The first, with the comments, provides some perspective on the neonicotinoid debate:
    http://www.nature.com/news/bees-lies-and-evidence-based-policy-1.12443
    The second is simply fascinating:
    http://www.nature.com/news/bumblebees-sense-electric-fields-in-flowers-1.12480

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  16. Wow! Thanks for the article. I’d always gone down the route of planting spring flowers for bees, as I’d been told was best. Will definitely look at getting those summer flowers out now instead. Thanks for the tip, and all the info, really great article!

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  17. For the most part, our bees also do better in urban locations here as well, unless they happen to be in an area where clovers are planted out, or land left entirely untended has regained an assortment of wildflowers. The invasives Japanese Knotweed and Purple Loosestrife, which appear along ditches and roadways, are also wonderful forage plants for bees. In my beeyard test garden, the favourite plants were catmint, Phacelia, Echium vulgare, fennels, dills and Joe Pye Weed (Eupatorium). The catmint bloomed June to November. In London, as in our suburban areas, a great deal could be done for bees by municipal governments, garden clubs and other interested parties if they backed and ran gardening efforts to provide bee forage (flower) corridors and linked patches (4′ x4′ grids of bee plants no farther than 1 km. apart). Every resident can plant a pot in a window, balcony or yard. Vacant land can be seeded in clovers, catmint, and bee blends. And we can all let dandelions flower; no need to cut them down. Most people see them with a new affection when they learn dandelions are important to bees.

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    • Emily Heath says:

      At least these invasives have some benefits! Thank you for all you do for the bees. I was horrified to see an advert on a local community website recently for synthetic lawn. The advert talked about the lack of mess and gardening needed for an artificial lawn. As if nature didn’t have enough to contend with, with all the decking and concreting going on, now there is another option to cover up soil and block plants growing.

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  18. Prof Ratnieks and the LASI team at Sussex University now have a series of interesting videos on Youtube. The one about plant choice is here http://www.youtube.com/watch?v=4u2LeTPGo9w

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