Something else many people don't realize, mandarinquat is very cold hardy, more so than calamondin.
One person commented that they seemed to be ready to pick by late September, when they still looked a little green and unripe, and had much more juice and flavor than when picked later in the Winter. It was growing in a container.
"Mandarinquats this year tastes excellent! I want more", calamondindave(Zone 8a, NC) , garden forum Houzz
Someone else commented that they had been growing kumquats and a mandarinquat outside in the ground in Seattle for a 3 years.
"Hybridizing cold hardy citrus to grow in the Pacific Northwest", Matt Hedlund, permies.com forum, beginning of 2018