A Plant in a Pot is Not the Same as A Plant in the Ground

Plants in pots are not as winter hardy as plants in the ground – we all know that – and most of us have lost our share of plants we had hoped would make it through the winter in a pot.

Thimbleberry plant in a tan pot

Thimbleberry in a pot

Often the issue is not winter freezing, but the thaw-freeze cycle of spring.  Native plants expect to freeze, but they also expect to have their roots nestled in soil that maintains warmer and more consistent temperatures than above ground.  Plants in pots are exposed to the dramatic changes in temperature often suffering root damage as they warm in springtime sunshine followed by freezing at night.

so… how to get potted plants to survive:

Avoid dark-colored pots that heat up quickly in the sun.  Unfortunately for those of us in the nursery business who use black plastic pots (used to keep roots dark during the growing season), avoiding using dark pots is not realistic.

A second option is to nestle pots in an insulating material that prevents sunlight from hitting the pot and keeps temperatures more consistent.  This may be accomplished with compost, straw, pine needles or whatever mulch material you use.

Third, consider moving pots to a shaded spot where sunshine won’t hit the pot in spring.  This helps moderate temperature fluctuations.

Stonecrop seedlings in nursery pots

Stonecrop in pots

Other tips:

  • Make sure pots have adequate drainage to minimize how much time the plants roots are sitting in water as the pot thaws in the spring.  Roots drown if sitting in water for more than a week or so.
  • Avoid overwintering in unglazed clay pots that crack as water in them freezes and thaws.

Most native species winter nicely in protected pots.  We’re experimenting with planters and have been pleased with the overwintering results.  Tell us about your experience with overwintering in pots!