Hi there and thank you for reading my question. I have yarrow that I planted three summers ago. It bloomed prolifically the first and second summers. This year? Nada. Nothing has changed in the bed it resides. Perhaps less watering this year than last year and the year before because more of its inhabitants are now established. The plant looks healthy and vibrant enough. I have not fertilized it, other than spreading composted cow manure in the spring. Any ideas why it didn’t bloom this year? Thank you!
Thank you for contacting Toronto Master Gardeners. Yarrow (Achillea) is usually an easy plant with simple growing requirements: full sun, average soil, moderate to low moisture and good drainage. The benign care you have given it should be sufficient. Yarrow USDA data base These needs should be examined first to be sure your yarrow is well situated. Has the growth of the other plants shaded it? is it sitting in a low spot in your garden where moisture might collect? is your soil dense clay? These conditions might be causing it to fail to bloom.How to grow yarrow
Yarrow has a fibrous root system and prostrate stems that root at the nodes and remain in the top 10 cm of soil. It benefits from division every three or four years. Although your plant is relatively young I suggest you dig it up this fall (mid to late September). It may be root bound from the nursery pot which would require you to spread out the roots to allow them to penetrate the soil. Or it may have root rot.
Examine the middle of clumps for root rot (due to poor drainage or too much water). Cut out and discard any mushy or dark part of the roots and reposition the healthy clumps about 20-30 cm apart depending on the size of the clump and how quickly your variety was spreading. Likely it will respond to this intervention.