[at_a_remove]

It isn't available yet, but they rediscovered what appears to be silphium in 2022. It checks all the boxes. It's a slow-growing plant, but they have started trying to propagate it.

[DonaldFisk]

Thanks. I've just searched for this, and the original paper is here: https://www.mdpi.com/2223-7747/10/1/102

[giardia]

Thank you, I hadn't heard about this.