I live in North Toronto (Lawrence and Mt Pleasant) so zone 5?
I have a tree peony in mid to late morning sun (almost full sun before a large black walnut leafs out. It’s situated along the edge of a wood chip path and faces south.
It’s in amended clay soil and is full and leafy. It hasn’t bloomed at all in two years and just one bloom the year before. I haven’t fertilized it at all in that time except for some compost (but not a lot).
I hope this is enough information to help me for next year.
Thank you for sending your gardening question to Toronto Master Gardeners.
What you are seeing in your peony is a gradual decline in its ability to get any nutrients from the soil. The problem is caused by a toxic compound emitted by roots of the Black Walnut (Juglans nigra) tree. Basically, it is smothering your peony.
Here is a link to one of our fact sheets dealing with this issue. We also have other published Q & A responses on our website.
We do not usually recommend transplanting a peony, but in this case, it’s necessary. Be sure to dig all around the roots to get as much as possible. Make a large hole and line it with organic compost. Place the peony in the hole with the “eye” (shoots) no more than 2.5 cm below the surface. Mulch around the peony, making sure not to come too close to the stem, and be patient, as it may take up to 3 years before it adjusts to its new surroundings and gives you the blooms you’ve been waiting for. More on peonies can be found on our website: