We get wasp nests in open ground and against our compost heap - it's a big open one. Usually badgers come along and shred them, leaving only a few confused and anxious wasps buzzing around. I expect this is the sort that got you bede. They never stay for long and disappear in a few days.
Thank you so for the thoughts, would be interesting to see photos of similar ant structures, I can't find anything online. A few extra photos including one showing a large collection of what I assume are newly hatched ants, they weren't moving and are a bit tricky to distinguish as ants but pretty sure they're not aphids, too big and shiny (plus they're on the woody trunk).
There hasn't been a tree guard. You can see there is black weed membrane around the trunk so the direct sun may have made it very hot underneath. We've had the drought conditions so a chance the nest got very dry and then flooded when the heavy rain hit but this is adjacent to a bed I've been watering so shouldn't be too dry.
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Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
There hasn't been a tree guard. You can see there is black weed membrane around the trunk so the direct sun may have made it very hot underneath. We've had the drought conditions so a chance the nest got very dry and then flooded when the heavy rain hit but this is adjacent to a bed I've been watering so shouldn't be too dry.
https://thediary.caerhays.co.uk/august/19th-august/
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.