The Leafcutter Diaries 3 – Balsam Days

One day while watching our Leafcutter, I realised that her behaviour had subtly changed.  Usually her foraging trips were short – she would leave to collect pollen and nectar and then return only a couple of minutes later.  Now her trips were 15-20 minutes long, and when she returned she’d started to land and rest near to the beehouse for a couple of minutes before resuming her nest building activities.

Her appearance had also turned a touch ghostly.

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Despite her now distinctly mouldy looking appearance I didn’t panic – I had seen this before in honeybees.  Our Leafcutter had found a patch of Himalayan Balsam somewhere.

Himalayan Balsam is a striking, pink flowering plant which grows to about 2m in height. It was introduced to Britain in the 19th century as an ornamental plant.  Unfortunately it is now one of the UK’s main invasive plant species.  It very quickly colonises and overcrowds native species, killing them off.  Despite it’s pretty appearance, it’s a bit of a thug – our apiary backs onto a riverbank where Himalayan Balsam grows, and each year we find strands of it growing straight through the concrete apiary floor.

Balsam

It’s very common on waterways – it is found on all of Lancashire’s main rivers.  I don’t have a major river near the house, but there is a brook about ten minutes walk away – this would also explain the increased length of our Leafcutter’s foraging trips.

At first thought, it seems odd.  Why would a bee expand so much energy flying to a plant some distance away, when there were perfectly good alternatives nearby?  One of the reasons that Himalayan Balsam is so successful in dominating other species is that the nectar it produces is so beloved by bees.  Given the option they will choose Himalayan Balsam over most native species of plant.  And when entering the flowers to get to the nectar, they are covered in the plant’s white pollen – which they then take to another Balsam flower.  Therefore Himalayan Balsam has evolved to ensure that it is very well pollinated – at the expense of the nearby native plants which suffer decreased pollination and therefore slower growth as a result.

While not a notifiable invasive species like Japanese Knotweed, it’s now widely recognised as a problem and parks, nature reserves and estates try to keep it under control by holding ‘balsam bashing’ days.

While I’m not the greatest fan of Himalayan Balsam for the reasons outlined above, our Leafcutter certainly seemed to be thriving on it.  She very quickly finished another nest tunnel.

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