FYI I have two Hinoki cypress trees that used to survive in the hardy winter in zone 3, we had some bad winter in Winnipeg in this year, I’m afraid my trees won’t make it. It is -1 outdoor which spring is approaching, do you think is a good idea to bring the trees (it is still in the container right now) to the indoor to check out the trees?
Thanks for your help in advance!
Thank you for contacting Toronto Master Gardeners about your two container grown Dwarf Hinoki False Cypress trees (Chamaecyparis obtusa ‘Nana Gracilis’). We wonder if the trees exhibit signs of failing health which prompts you to consider bringing them indoors to check their viability.
Horticultural sources suggest the Hardiness zone for this plant as 5a or 6, and growing in a pot reduces winter hardiness by about a full zone. I note that Winnipeg is listed as Zone 3a. Clearly you have successfully grown them in your cold climate.
It is essential that containerized evergreens be well watered right up to freeze up because they continue to transpire during the winter and cannot replace this moisture from the frozen potting medium. It would help to water a little on non-freezing days because weeks without moisture can cause roots to freeze-dry in a pot. A thick mulch in winter can protect the plant in exposed locations or colder microclimates.
Taking your pots in now to check on their health, on the cusp of Spring, would be of little help, I believe. Now that temperatures are ranging into positive territory it would be beneficial to apply some water to the containers.
A Toronto Master Gardener response in our archive https://www.torontomastergardeners.ca/askagardener/container-gardening on-terrace/ provides information which may be of interest to you.
We wish you every success in the care of these fine trees.