It's the nearby trees feasting on the buffet you put out for them. This happens with my vegetable bed every year. The roots from a nearby maple creep in. I have to tame them back with loppers or bypass pruners. Perhaps you need to relocate your compost pile.

Its likely the sycamore saplings invading the compost - you'll need to either remove those from the ground completely or move the compost set up. If they're Acer pseudoplatanus saplings (common Sycamore) you probably don't want them anyway, they get huge...

I was given three old potato bins, used by farmers to collect potatoes off the land years ago, before the Harvesters were invented! These are big bins about the size of a pallet each side. They arrived as a donation to the bonfire heap as they were not needed. Much too good for that and were put to use as compost bins. Of course we all position them out of the way where we don't want to use the land. Mine has roots of nettles which invade. Not much you can do without cutting off the bins from the soil completely which rather defeats the object. Your's look as if they might be the little yellowish roots from the Ivy, it's a bit like that, loves fresh soil, time-consuming but not difficult to remove.

'Just watch the ivy on that old garden wall
Clinging so tightly, what e'er may befall
As you grow older I'll be constant and true
And just like the ivy, I'll cling to you.'

I had ivy invade bags of leaf litter and they looked just like that.
I moved the bags to a different area and the problem is no longer there.

Hello,

Thanks for all the comments.

It seems like the options I have are either move the heaps or put down some kind of root barrier underneath. Even, perhaps, put them on pallets so they're lifted off the ground.

How important is contact with the soil? Before I built them I must have read somewhere that giving access to worms was a must, but I guess people do make compost on hard surfaces (concrete, etc.)...?

When I've lifted the heaps from where they are, will the roots that have grown through them rot down reasonably quickly? Or, will I need to pick through it by hand to get out the material that's ready to use right now? I don't want to have to leave the heaps for another year before I can make use of it!

Thanks,

Piers.

Hello,

Update and a follow up question:

Back in March I put the contents of the compost bin in one of those giant builders sand bags so that it was no longer in contact with the ground, and left it for the last two months. I've now sieved through the lot, and got about 90 litres of nice compost, and a pile of roots, twigs, etc.

Having been separated out, is it safe to put the roots etc. into my starter heap (the one that gets this year's waste), or will they regrow (in which case I should burn or dispose through the council)?

Piers.

personally i'd put them in the council greenwaste bin