Stepping up for our pollinators: bumblebees
With climate change adding to habitat loss and pesticide woes, how can we step up for bumblebees in our gardens?
It can’t have escaped your attention that this year has been abysmal for pollinators. Butterfly Conservation recently declared a Butterfly Emergency after results from the Big Butterfly Count – an annual citizen science count of butterflies in parks and gardens – pointed to 2024 being the worst year on record for butterflies, after years of steady declines. Bumblebee Conservation Trust hasn’t released its Bee Walk data on this year’s bumblebees yet but my feeling is it’s going to tell a similar story. Where were they all?
I looked at this in my first Substack post. While pollinator numbers have been declining for many years thanks to a combination of habitat loss, pollution/urbanisation and pesticide use, there has been a noticeable crash recently, with usually bee-friendly flowers suddenly empty in many parts of the country. A lot of this is to do with weather – as our climate changes and weather becomes more extreme, our insects are struggling – they just haven’t evolved to deal with this.
After the great drought of 1976, some butterfly species took 10 years to rebuild their numbers, while others (thanks to the combined assault of habitat loss) never recovered. It makes sense, then, that the drought of 2022 impacted pollinator numbers as well. And since then it’s barely stopped raining – another challenging extreme. Here in Brighton, since the summer of 2022, we’ve had two very mild wet winters, two very cold, wet springs and two cold-ish wet summers. If you’re a bee or a butterfly or a fly or a beetle, and you’ve evolved alongside cold winters, mild springs and warm summers of sunshine and showers, you’re going to be in trouble when the weather doesn’t behave as it should.
So what can we do? And will anything really help? I can’t stress enough that restoring habitats, ending fossil fuels and reducing our meat and dairy intake are the only ways to secure a better future for us and our wildlife, so please do keep banging that drum (and if you’re not banging it, start!). And good things are happening – there are brilliant examples of habitat restoration happening all over the country, including recent good news for the shrill carder bumblebee , but there’s plenty we gardeners can do to further help the cause.
Bumblebees
There are so many pollinators that if I included them all in this post it would be far too long. So today I’m going to write about bumblebees. I’ll write about other pollinators in due course.
The bumblebee lifecycle
Let’s start with the bumblebee lifecycle. Unlike honeybees, bumblebee nests are annual. Each nest is founded by a queen, who has hibernated over winter. In spring she founds her nest, making a clump or ‘brood cell’ of pollen, on which she lays eggs, fertilising them with sperm ‘collected’ the previous summer. She broods the eggs like a bird, shivering her flight muscles to keep them warm (a constant temperature of 25-32ºC), and keeps herself going with a little wax pot of nectar she made earlier. When the grubs hatch out of the eggs they first eat through the pollen clump the queen prepared for them, but once that has run out the queen has to leave the nest to gather more food. (She mixes pollen and nectar into a watery ‘honey’.) But she can only pop out for short periods, as she still has to keep the nest warm, otherwise her grubs and any further eggs will die. This is a critical stage in the life of the bumblebee nest and many don’t make it. If the nest does survive, the queen continues laying eggs while the workers go out and gather pollen and nectar for the new grubs in the nest. Towards the end of the season, the queen lays eggs of males and daughter queens, which mate with males and daughter queens of different nests before the original nest and males die. The daughter queens enter hibernation with their store of sperm, hopefully not to be seen again until spring.
What happened this spring?
This spring I was relieved to see that many queens had made it through the wet winter. But then conditions got cold and wet again, and they disappeared. It seems sensible to assume that conditions turned bad just at the point many bumblebee nests were at their ‘critical stage’.
Something else I noticed was how the rain was destroying flowers, particularly crocuses. Crocuses are important for bumblebees as they’re full of pollen and nectar but also because they close at night – a bumblebee queen that hasn’t started a new nest might even sleep in one. I’ve seen large swathes of closed crocus flowers with bumblebee queens clinging on to them as if willing them to open. Despite hibernating for up to seven months, a bumblebee needs a regular supply of nectar to keep her going and will quickly die if she can’t find food. On top of this, bumblebees don’t fly in heavy rain.
So, with the heavy rain that bumblebees don’t fly in, the cold conditions probably making it harder for queens to keep their nests warm, and destroyed crocuses probably making it harder to find food, it struck me that we gardeners need to double down on our efforts to provide flowers and nesting opportunities for bumblebees (and of course other pollinators) in spring. The more flowers and nesting opportunities there are, the less distance the queens need to travel to collect food to take back to the nest, so the better chances the nests have of surviving.
But I also wondered if it’s time to grow flowers undercover, so there would be something in bloom no matter what the weather, a sort of Center Parcs for bees if you like. Could this contribute to the chances of an early nest surviving?
Kate, what are you talking about?
Like many gardeners, I have a greenhouse. And, like many gardeners, I don’t really use it in winter (although lately I have been growing a bit of garlic in it). Bumblebees fly in and out in summer to pollinate my tomatoes. What if there were flowers for them in spring, as well? Flowers that were protected from rain, that bloomed a fraction earlier than everything else because conditions were warmer? That they might sleep in before they find a nest site? Could I make a difference?
I doubt I’ll ever know, but I’m going to try it, and I thought you might like to try, too.
In the greenhouse I’ve planted two strips of organic crocus corms. (Organic because non-organic bulbs and corms are likely treated with neonicotinoid pesticides, and they’ve got enough to deal with at the moment.) I’ll keep the corms watered but not over-watered, so the flowers produce lots of nectar but last longer than they might do outside. I’ll also plant a few pulmonaria and primroses, which bees and other pollinators also love, but save space for garlic and – later – tomato plants, so I can still use the greenhouse for growing food. A little clump of straw in a corner might keep them comfy if they decide to stay overnight and don’t want to sleep in a crocus flower. Obviously I’ll leave the door and windows open.
I can’t change the weather, but I can provide a dry, nectar-rich habitat with some cosy overnight options. That’s got to be worth a try?
Outside I’ve planted a new pot of winter heather, which flowers from December to March and is far more robust than crocuses, so should serve bees and other pollinators in all conditions. This will complement my other early spring flowering plants, of which I have nearly all on the following list (I’m just trying to find space for mahonia and willow):
My favourite early spring flowers for bumblebees
Comfrey, Symphytum orientale (the earliest comfrey to flower)
Crocus
Dandelions - not the best bee flowers in terms of pollen, but they bloom early and provide much-needed nectar
Hellebores (Helleborus niger/ hybrids)
Lungwort (Pulmonaria)
Mahonia
Native primrose (Primula vulgaris)
Perennial wallflower (Erysimum ‘Bowles’s Mauve’)
Willow (in small gardens try Salix caprea 'Kilmarnock')
Winter heather (Erica carnea and Erica x darleyensis)
Winter honeysuckle (Lonicera fragrantissima)
Note daffodils aren’t included here. They tend to be avoided by bumblebees, probably because they are slightly toxic. Other bee species (E.G. hairy footed flower bee), will visit daffs.
For later spring flowers and beyond, Dave Goulson has an excellent list here
Make a bumblebee nest
I’ve been trying to attract bumblebees to nest with me for years with almost no success – they finally nested in a big habitat pile I’d made on my allotment. If you want to follow instructions on making a nest here’s some from Dave Goulson but you could also do the following:
Let areas of grass grow long
Make a log/stick pile and let grass grow up through it
Be nice to mice, as bumblebees often seek old mouse holes to nest in
Make an open compost heap and leave it along from spring to autumn
Ultimately, with continued habitat loss and the ever increasing threat of climate change, we need to do far more for our bees and other pollinators. If you don’t have a greenhouse, do you have space for a pot of winter heather? Can you use your conservatory, porch or other covered space to grow crocuses? Can you dedicate a space in which bumblebees might make a nest? The more we do, the better their chances. It really is that simple.
Drop me a line in the comments to share how you are stepping up for bumblebees this growing season. Maybe, just maybe, if we work together, we can help them through their critical stage, and there will be more of them next year.
Worth noting that Peter Nyssen’s bulbs are not treated with neonics.
Love the idea of using my greenhouse this way! I'm going to give it a go. Thank you! x