Wintering Sheds: Why are more North American beekeepers overwintering their bees in cold storage?

More and more US beekeepers are starting to place their bees in sheds for the fall, for indoor wintering. While beekeepers in Canada have done this for decades, the popularity of the practice in the US is more recent. Beekeepers began by using structures already built for onion and potato storage in Idaho to house their bees in the fall. These beekeepers then remove the bees in January, and bring them to California for almond tree pollination. Many beekeepers are still using old potato and onion sheds in Idaho, but as the popularity of this practice has increased, some beekeepers have built sheds just for the purpose of overwintering bees. These sheds are far from the dirt floor, onion and potato sheds of Idaho. They are clean, new structures with air filtration and ventilation systems, vacuums, Carbon Dioxide and Oxygen monitors, temperature monitors, and cooling systems. Why are more beekeepers choosing to use cold storage and winter their bees indoors?

A clean, newly built wintering facility

I surveyed beekeepers on the Midwest Tech-Transfer Team, asking them why they put their bees in sheds. While the most candid beekeepers admitted they want a vacation for themselves after a long, hard year (they can take some time off instead of working to keep their bees fed and healthy in California), all the beekeepers storing bees in sheds believe the practice is good for the health of their bees.

Bees inside an indoor wintering facility


Here are some of the reasons beekeepers gave:

  1. Bees in sheds are dormant, so beekeepers don’t need to buy sugar or spend time feeding and working colonies. This can save beekeepers money, since the California landscape in Nov/Dec cannot support colonies without supplemental feeding. The bees in sheds are not flying, foraging, or rearing brood (activities that require a lot of energy), so they can conserve energy and build up body fat.
  2. Wintering sheds stay cold and dark, so colonies are broodless. Some beekeepers consider this broodless period to be a mite treatment, because Varroa mites are not able to reproduce without brood. This means that mite numbers will not increase, and mites in the colony may die or get too old to successfully reproduce. Therefore, colonies could potentially begin almond pollination with low mite loads.


  3. Since the colony goes through a “winter,” and is dormant, the queen does not lay for a period of time. This gives the queen a break from laying eggs. Some beekeepers said that this break increases queen longevity.
  4. When the colonies are put on the ground in California, they experience a dramatic change in temperature. The queen starts laying again very quickly, which some beekeepers said leads to a population boom. If the colonies spend the winter in California, the temperature is variable, and increases slowly in February and March, causing the bees to ramp up their brood production through a slow process. Some beekeepers said their shed bees look healthier and bigger during almond pollination, and said this is likely due to the quick jump these colonies make to rearing brood again.
  5. Bees build up Carbon Dioxide within their colonies when they are in a confined space where ventilation is restricted. Letting CO2 levels build up too much can kill bees, but since mites are smaller, it takes less CO2 to harm them than it takes to harm a bee. Some scientists are working to find a “sweet spot,” meaning a CO2 level that is not harmful to bees but is to mites. While beekeepers are not relying on sheds as their main mite treatment right now, many beekeepers have hope that with further research, it could be the key to starting the year with healthy bees.




Thank you to all the beekeepers who answered my questions, and for Steppler Honey Farms for allowing me to use their photos!

Written By: Phoebe Koenig

Phoebe Koenig has written 5 post in this blog.


2 Responses to “Wintering Sheds: Why are more North American beekeepers overwintering their bees in cold storage?”

  1. daveharrod

    How cold do the sheds have to be? What happens if they warm up? Do the onion sheds stay that cold? (I’m not really sure what an onion shed is exactly).

  2. Bobainturuncle

    Good question. I have been involved with bees for 4 years and in that time I have immersed myself in their lifestyle in an effort to make up for lost time. There is no question bees are the most studied of insects. I started with 1 hive and now have 6 by choice and no more. I too wondered about temperature and bees. I live in Canada and as I write this it is -15C. This year I am experimenting with keeping nucs and mini nucs in an insulated shed I have on my property. The idea is to see if 1. Can I control the temperature? 2. How much electricity will it take to operate? 3.What emergency steps do I need in case of power outage? 4. What ventilation can I install to exchange air without losing heat too greatly? The optimum temperature to keep the bees at is 6 degrees Celsius + – 2degrees. Complete darkness. If the temperature is too high the bees will break cluster leaving the queen susceptible to cold. Not that she would not survive, it’s just that if she lays any eggs and the bees fail to cluster again because they are comfortable, the eggs are in jeopardy if the temp gets too low. The bees would re-cluster but too late to prevent brood chill. If there is any light and it is overly warm the bees will fly because they are fooled into thinking the temp is warming up and it is safe to leave the hive. However in this case the temp is artificial and if they do leave the confines of the heated climate and enter the real world they will of course die. The reasons why beekeepers want to keep bees inside are numerous. For me it is a matter of economics. To be able to sell nucs and queens as early in spring as possible. Also to be able to requeen my own colonies if needed. It is a delicate balance we as beekeepers try to perform with an organism that is not supposed to survive in this manner. Onion shed is just a cold storage building to which some form of temperature control and air circulation is provided.