Question
I have a large Japanese Peony which I would like to divide as it is getting too big for the area in which it now resides.  Can you please tell me the best time of year to do this and how it should be done?  I live in Calgary, Alberta and the peony grows really well in my south facing yard.

Answer
Barbara, the best time to divide pernenials is in the early fall. That gives the plants sufficient time to establish their roots prior to the first hard frost. They also experience less transplant stress because of the cooler temperatures and shorter days.

As with any perennial, the plants need to be divided every 3-5 years. To do so, lift the plant by digging carefully 1 foot outside the perimeter of the plant. Then stick a sharp spade through the middle of the root system. Depending on how large the plant is, you can probably make 3-4 plants out of the one.

Next spring, feed the plants with a 10-10-10 balanced fertilizer. Mulch the plant moderately with shredded bark or aged grass clippings to hold in moisture and to keep the temperature of the soil more consistent.

Unfortunately, peonies may not bloom the first year after dividing. But given the proper care described above, they should flower the following five years until they need divided again. If you divide the plants now rather than waiting until fall, you have a 50/50 chance that they will flower next year. You just have to be sure they stay well-watered and mulched due to the heat and stress they will endure this time of year.

I hope this answered your question. Please write again if I can ever be of assistance.

Regards,

Mike