One of the less spectacular plants which you will probably see growing by the railway lines and not so much in a garden, but quite beneficial for the soil. That was the reason I went on a quest to find some. There was a stall on our local Saturday morning market where all sorts of herbaceous plants could be bought. The stall holder had no tansy on the stall, but said it would be no problem. He took my address and after the market closed he called by with a few tansy plants. This was many years ago and since it returns every year in the garden.