[Lottie Mary]

I have three long established rhubarb on my allotment - inherited from the previous tenant.

All but one have bolted - I too was wondering if there is anything I may have done wrong, or if they bolt because they're old and need to be separated?

[Trillium]

No, you didn't do anything wrong. All plants want to flower, it's their natural way but some just don't know their seeds are useless.

Since yours is a long established group, it wouldn't hurt to dig them up, divide, feed the new planting holes and set the divisions back in. But if you want rhubarb this year, I'd wait until early fall to do this when they have the winter to recover.

[Yorkie]

Just make sure you remove the flower spikes, cut or snap them off at the base.  If you leave the spikes on, the plant puts its energy into them rather than the edible bits!