Ask Mr. Smarty Plants

You are correct that Achillea millefolium (common yarrow) can be quite invasive. Transplanting it suddenly into "new dirt" in a big pot may have been too much of a shock for even this tough plant. One problem with transplanting any plant is to prevent wilting from respiration of moisture from the leaves. Often in transplanting, it pays to trim back as much as one-third of the plant material to minimize water loss from the plant. Also, it's difficult to get enough water into very dry potting soil at first. One good way to make sure it's wet all the way through is to fill the pot and then stand it in a basin of water, letting the water soak up from the bottom, then let it drip and drain before you make the transplant. At the same time, you don't want soggy soil, as that will just drown the roots, already suffering from the shock of being taken from their original planting. All this having been said, your question about whether these plants will survive has still not been answered. Possibly trimming it back now would help it survive, but that very well could mean no blooms this year, since yarrow blooms in early Summer. Also, although it's a full sun plant, it could probably do with a little shade part of the day, again to cut down on the transplant shock. In summary, you may be able to help the plant survive and bloom another year. And, in future, you might choose to do your transplanting when the plant is more dormant, perhaps in the Fall.

Achillea millefolium