At the end of the summer we see a lot of white bees around, a sure sign that they have been collecting nectar from Himalayan balsam. Here is a honey bee emerging from a balsam flower covered in white pollen.
The bees seem to find the pollen a nuisance or an irritant and spend a lot of time scraping it off.
One place they cannot reach is the back of the thorax so they end up with a very characteristic white mark when they get back to the hive. I don't know where balsam grows close to my home but the bees have certainly found it.
Honey bees seem to collect very little of this pollen. This bee has a small amount in its pollen baskets but nearly all the pollen being brought in is from other flowers (and is of other colours). The bees are very fond of the balsam nectar but the pollen is presumably not of the quality they are after.
Bumblebees are also very keen on the nectar. This bee has its tongue out even before getting into the flower.
Bumblebees seem also to dislike the pollen. I haven't seen a bumblebee with white pollen in its baskets. This common carder bee had been collecting brown pollen before stopping by for the nectar.
The bumblebees also spend a lot of time grooming to get rid of the pollen. These two show how they can't quite reach the small of their backs with their middle legs.
This is a solitary bee emerging from a balsam flower but it has so much pollen on it that it is difficult to tell what species it is.
Wasps are enthusiastic visitors for the nectar as well.
The Himalayan balsam flower is beautifully designed. It has a landing platform at the front but the nectary is right at the back. Here there is a small drop of overflowing nectar.
The bees pass through the flower and under the anthers in the roof of the flower, getting covered in pollen as they do so.
The flower is in two parts so they sometimes emerge through the side but almost always seem to go in the front.
The fertilised flower produces a seed pod which distributes its seeds with explosive force and ends up with the spring sprung like this. A single plant produces up to 800 seeds. The seeds can end up up to 4m away but as the plant commonly grows at the waterside the seeds can obviously travel much farther.
Himalayan balsam (Impatiens glandulifera) was introduced to the UK as a garden plant in 1839 but soon escaped into the wild. It is a non-native invasive plant listed on schedule 9 of the Wildlife and Countryside Act in England and Wales. It grows very tall and out-competes native plants thus promoting riverbank erosion. It is widespread throughout the UK. This photo shows how it has spread along the banks of the river Nene in Northamptonshire.
There is another non-native balsam found on our riverbanks - orange balsam, Impatiens capensis. Also known as orange jewelweed, it is a native of North America but seems much less invasive than Himalayan balsam over here.
It seem that we are stuck with Himalayan balsam. It is much more widespread than other alien invaders such as Japanese knotweed and giant hogweed and will be impossible to eradicate. The bees won't be complaining though as it is their favourite source of nectar at this time of year.