A colleague of mine in Eastport, Catherine Lee, recently asked me if I could help her solve a peony mystery. Her peonies stopped blooming two years ago, presumably because the site where they were originally planted many years ago has become too shady with the growth of nearby trees. Catherine knows that peonies, at least in the north, need full sun. So she moved some of them to a sunnier spot and, after two years, they have yet to form flower buds. We both wonder why.

Like hostas, day lilies and roses, peonies are the kind of plant for which societies are formed and books written. They are described as free-flowering and easy to grow, yet the American Peony Society has developed an extensive diagnostic key for failure to flower. Looking this over, I dismissed the six possible reasons why buds appear but fail to develop – including death by late frost, thrips, disease, waterlogging, heat, and starvation – and paid particular attention to the six reasons why buds never appear.

Catherine, moving your peonies out of the shade is the right thing to do and you should go ahead and move the rest of them to a sunny spot. However, peonies also resent being moved and respond by failing to flower for one or more years afterward. Still, you have no choice and, once they begin flowering again, they should bloom reliably for a decade or more without missing a season.

When you move the rest of your peonies, pay close attention to planting depth. Another cause of failure to flower is planting too deep. According to studies conducted by Dr. Abe Halevy in Israel, deep planting results in lack of light reaching the developing flower buds and flower initiation does not occur. The buds on the rootstock of transplants should be no more than 2 inches below the soil.

Flowering in peonies, as well as other herbaceous perennials, can also be reduced by excessive nitrogen application.

A light feeding in spring with a low nitrogen fertilizer such as 8-8-8 is recommended. I recall that we dismissed too much nitrogen as a probable cause in this particular case.

My money is on the finicky nature of peonies when it comes to being moved around. I even think I understand this behavior. I imagine a large portion of the root system left behind during the move and the subsequent need to replace those roots before expending energy on flower bud development.

So go ahead and move them all, keeping an eye on the depth of their buds. Give them a sunny, well-drained spot and abundant water in the spring when they are vigorously growing. Feed them compost tea or a low-nitrogen fertilizer. Eventually your care and patience will be rewarded.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605. Include name, address and telephone number.