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Containers in Winter

Containers in Winter

As you look out onto your deck or yard this winter you might be wondering if those container plants that you never did anything with will survive the cold. Perhaps they are perennials or shrubs you intended to plant but never got into the ground. Or maybe they are shrubs that you want to stay in the pots, so you’re hoping that they’ll live through the winter. At this point in the season some people are also feeling guilty that they never got any mulch or other cold protection around these plants. Here are some helpful tips for all of these situations.

  • A plant that’s being left outside should be in a container made out of wood, fiberglass, plastic or other non-breakable material. If your plant is in a clay or cement container and it’s still possible to pull it into an unheated shed or garage, do so. The pot is more likely crack if left where it will freeze to the deck or ground. As the sun warms in late-January and February, the top of the container can expand while the bottom is held fast, frozen to the soil or patio. This tension between the thawing top and the frozen bottom can cause torque that cracks the pot. If it’s impossible to put breakable containers into a shed or garage, prop them up off the ground with three small pieces of wood. Doing this during a warm spell in January can help prevent a cracked pot in the spring.
  • In general, the soil in frozen containers gets about twenty degrees colder than ground temperatures. So if your plant is hardy two zones colder than where you are the plants should survive the winter. The larger the pot, so the more soil is around the roots, the better. Here on Cape Cod most of us are in a warm zone 6 or a cold zone 7. So if your perennial, shrub or small tree is hardy in zone 4 or below it should be fine when left outdoors.
  • Some winters are colder and drier than others. If the temperatures have been above freezing for a period of time, and it hasn’t rained, be sure to check to see if the soil in the containers is dry. Evergreens are more prone to drying than perennials or deciduous shrubs, so check these at least once a week. When the soil is frozen there is no need to water. Check those plants you’ve pulled into the shed or garage regularly as well, watering when needed.
  • Any plants that you’ve pulled under cover might start to break dormancy in late-February or March. Be alert for swelling buds and pull the container outside if the plant is hardy. Tropicals will need to wait until May, but hardy plants can be allowed to break dormancy outdoors, later in the spring.

    The weeping pussy willow in this pot is a plant that's commonly sold in the greenhouse early in the spring. Since the weeping part is grafted onto the trunk, it will never grow any taller so it makes a better potted plant than a landscape specimen. Fortunately, it is perfectly hardy and has remained outside in this container for over 8 years.

2 Comments

  1. Mary JO Burton on January 24, 2014 at 2:12 pm

    Thank you, I always wonder why some of my pots break and some don’t. see you soon for some more birdseed and suet !!!!

    • CLFornari on January 24, 2014 at 2:15 pm

      Mary JO – some are also just more fragile than others…
      See you in the Bird aisle soon!

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