I have those. I pull the bulbs out of the ground to thin them out as soon as they finish flowering.

The ones I have need to be dug up as they're about 12 inches deep and just pulling on the leaves breaks them away from the bulbs.
So how do they spread, by seed only?

Hi I think they spread underground as well.

Bluebells spread both by seed and by increasing offsets or baby bulbs in the ground. I'm afraid,if you want to control them, then both deadheading prior to seed formation AND digging down deep enough with a full sized garden fork or spade to get out the bulbs in the ground is necessary.

Daffodils are less likely to spread by seed, mostly by increasing offsets in the ground.

Bamboo is right, and they're difficult to eradicate. I thought I'd got rid of all the bulbs (I much prefer our native bluebells) but the odd one keeps popping up!

Thanks.
So I could remove the spent flower heads to prevent seeds but there are literally hundreds of bluebells and digging out all the bulbs would be backbreaking!

One thought I had was to spray them all with weedkiller next Spring, as the leaves emerge.

you could spray them this year before they die back. the systemic weedkiller will be taken down into the bulb and kill it.

Yes, thought about that.

But the problem is, the bluebells are smothering the perennials that are in growth and trying to spray the bluebells would be so difficult without getting weedkiller on the perennial foilage.

So if I wait until next Spring, I could spray the weedkiller on the bluebell foilage as it emerges before the summer flowering perennial foilage emerges.

To be honest, I've never found weedkiller works on bulbous plants, I really wish it did so I could easily get rid of the white flowered alliums that are everywhere, but maybe there's a higher chance of success after flowering is over,not sure.

That's a new one. Didn't know weedkiller had no effect on bulbous plants ...

Well, if Seaburngirl says its works, maybe it does, but I've never had any luck using it. I used glyphosate, variable results generally I find, but didn't seem to touch the bulbs...

it has some success on bulbs but I can see why you want to spray as it emerges.

Is the reason, or could the reason be, that weedkiller's don't have the same effect on bluebells etc, because their leaves are waxy and therefore don't absorb the weedkiller in the same way other foilage does?

Not sure - the leaves on the alliums I'm trying to get rid of aren't waxy, but the blasted things seem untouched by the weedkiller regardless.

Maybe a stronger weedkiller would be more effective, i.e. SBK stump killer?

I had far too many bluebells in my garden hybrids mostly between Spanish and English. I regularly pull off the leaves and spent flower heads. I hope by pulling from where the leaves go underground I am denying the bulb the nourishment it needs to live. My bulbs are also deep in the ground. I seem to be having some success. The perennials are not affected by the bulbs only the foliage which looks messy and can hide your emerging plants. I know the daffodils multiply by bulbils (baby bulbs around the parent bulb). These need to grow big enough to reach flowering stage.

Using SBK as a spray isn't a good idea, you don't want residual SBK in the soil, particularly where other plants are already growing.

Thanks Bamboo.
I contacted Vitax about using SBK and they confirm it will not kill bluebells anyway.
In the meantime I dug most of them up, with a lot of help from two younger (Fitter!) friends. Now left with a huge heap of spent flowers, green juicy leaves and bulbs, over a wheel bin full.
Just wondered, could the leaves be used as a mulch around the base of plants to add nutrients to the soil as they decompose, instead of filling a wheel bin with them?

pull the leaves off the bulbs and compost the leaves. the bulbs will have to go in the normal bin or they will lie dormant in the compost for next year.

So the leaves aren't suitable as a mulch?

Not really, Richierich, fresh green leaves are always better composted properly, and they are a great addition to a compost heap or bin. You could put them on your borders, but you will be depriving the plants in the borders of some nitrogen, because nitrogen is required to break down the leaves you've put on the border....and they'll look pretty ghastly anyway. Better to compost them, then put the resulting compost back on the border.