How to Grow Shrubs in Pots
We get asked all the time: Can I grow a shrub in a pot?
The answer is never a definite yes or no. A lot of factors go into a shrubs long term survival in a pot.
The problem with growing perennial plants and shrubs in pots is from Chicago's brutal, unpredictable winters. Because the sides of the pot are exposed to the air, the soil in the pot thaws out on days the temperature gets above freezing and then re-freezes every night when the temperature drops. This is very bad for plants. The roots of plants in pots can also be exposed to sub zero temperatures they would never experience if they were planted in the ground. Plants are considered hardy when planted in the ground in Chicago, but not when they're in a container.
If you have your heart set on it, then try it! Here are some things you can do to increase your odds of success to the 80% range. That's better odds than you get in Vegas.
Choose A Big Pot
The soil in larger pots is less likely to freeze and thaw so quickly because of the volume. Also, terracotta and thin plastic pots are not good choices. They can crack easily in the winter. Foam, fiberglass or wooden containers are better choices.
Protect Your Pots in the Winter
Placing pots in an area where they are less likely to thaw out will increase your odds of success. The north side of a building or inside an unheated garage (for non-evergreens) are good choices. You can also plant it, pot and all, in the ground just before winter. This way the soil in the pot can't thaw out until the ground does in the spring.
Check Them For Water
Make sure that you water them well just before winter. Bone dry roots are unhappy roots. Check your plants several times over the winter to make sure they are still moist. Water them if necessary.
Evergreens never lose their leaves, so not only do they need sunlight in winter but they also dry out more quickly because of water lost through all those leaves or needles.