Growing citrus outdoors
If you are in a temperate climate, you may ask: Can my citrus plants grow in the garden?
The answer is: yes, all citrus species grown in a pot can be placed outdoors during the warm season. You can also place them on a terrace or in a greenhouse. However, when winter comes, you’ll need to move the trees to a frost-free place (see: Overwintering citrus).
Frost hardy citrus
Besides common citrus, which can handle only light or moderate frost, there are species which can handle harsh temperate-zone winters. The most cold hardy citrus is the trifoliate orange, which can grow inground in Poland and in countries as cold as frost hardiness zone 6 USDA (or even in zone 5).
Learn more about frost hardy citrus: