I'm not sure if wormwood has allelopathy issues. It's possible but I don't know either way. Try googling and see if you get some info on that. Use the botanical name in your searches. It will cut out some of the noise you'll have to sift through.

I do know that some of the other echinacea are slower to get started than E. purpurea. From my own experience E. paradoxa, E. tennesseensis, and E. angustifolia are all slower to get going after transplanting and just slower growers in general than E. purpurea. I've had the E. tennesseensis about 5 years and I bought it as a plant. It wasn't until last year that it really took off with a lot of blooms.

As far as wormwood, if it is as hardy as mugwort (A. vulgaris), dig it up and move it. You won't kill it. ;)

FataMorgana

I have plenty of stuff growing right next to big wormwood bushes. Except that the wormwood grows quickly and tends to shade out its neighbors, I've had no problems. Many perennials take a while to take off. It sounds like you may also have problems with overcrowding or shade.

Hey there,

Don't know whether this is true, but I read not to grow wormwood around certain plants because the roots emit a toxin which kills them. Apparently it does this to ensure no other plants take up it's water, nutrients, etc. Again, don't know if this is true, but if it is, that would be the answer.