Rose Mallow – overwintering in a pot

(Question)

Purchased a Rose Mallow perennial hibiscus in August. Decided to place it in a large pot – about 2 feet diameter and 2 feet tall since could not decide where to plant it in our property at that time.

Now after today’s frost (Sundary Oct. 18), the leaves withered considerably and wish to winterize in the pot. We have access to pine needles, boughs, and possibly some straw. Do we have to use styrofoam around the pot in addition to the mulch to maintain a steady soil temp in the winter? Might half burrowing it in soil and covering with the boughs be enough without the styrofoam (environmental concern re styrofoam)? Any other options?

 

(Answer)

 

Thanks for the question about overwintering a potted plant.I hope we aren’t too late to help you.

Sounds like you have chosen a very large pot which is a good start. The issue for your rose mallow (Hibiscus moscheutos) is that the roots must be protected over the winter. Young roots on the periphery of the pot are most vulnerable.. Your zone in Erin is 5A according to the Landscape Ontario web site. A usual recommendation is to pick a plant that is one to two zones below your own zone to overwinter in a pot. This is not your case.  Your plant is hardy zone 5 to 10. So it is a very close call.

If you can dig the pot into the soil that is best. This can be temporary. If you can’t dig it in, do you have room in the garage? The plant does not need light during the winter but does need some watering.

If it must stay outside find a place with soil beneath it. North and Eastern side of the house. Out of wind and changing exposures. I understand your not wanting to use styrofoam at lots of levels. It is best inside the pot and at this point you do not want to disturb the roots. Use hay, needles, leaves. Use lots. Protect the roots with this added heat source. Are you worried that the pot could break?

I hope these comments are of help to you. In the Spring reverse all this care to allow your plant to grow properly. Prune back in early Spring. Watch for pests like aphids, white flies, Japanese beetles. Find a good home for it in the spring and enjoy the largest perennial flower in your garden.

https://www.torontomastergardeners.ca/askagardener/overwintering-plants-in-pots/