Saturday, November 16, 2013

Succulent Winter Quarters

Over-wintering My Cacti and Other Succulents

I over winter the bulk of my cacti and other succulent collection in two 5 x 8 ft. (1.5 x 2.5 meter) wooden boxes (shown below) that are covered with 6 mil plastic  and heated with a 1200 watt electric heater.  This over wintering method provides two desireable features. First, much like a greenhouse, it provides excellent winter light for the plants.  Second, it allows a relatively low night temperature, usually around 42 degrees F. (5.5 degrees C).  I've found that many succulents flower better when given a cool night temperature over the winter.  Basically, this is a low cost alternative to a greenhouse.  

The frames are covered initially with a single layer of 6 mil clear plastic.  When night temperatures begin to drop below 20 degrees F. (-6.5 degrees C), a second layer of plastic is added.  The plastic is draped completely over the frames and held in place with six cinder blocks per frame.   

The frames have proven successful in tempertures as low as 5 degrees below zero F. (-21 degrees C), and in snowfall depths of 25 inches (63 cm).  There are two major problems with this system of over-wintering.  First, a loss of electricity can drop the temperature in the frames to a plant damaging level within 4 hours.  To handle such an emergency I have two backup generators that can be used to keep the frames heated until the power is restored.  The second major problems is very limited access to the plants over the winter.  I do not remove the plastic unless the outside temperature is above 45 degrees F. (7.2 degrees C).  Occasionally two weeks can pass without being able to open the frames.      

I have been using these over-wintering frames for the past 12 years and they have performed well.  They cost less than $300 dollars to build (the biggest expense is thermostats for the heaters) and the monthly electricity cost average about $40 for both frames.


  1. Very interesting how you over winter your plants. Do you remove the snow from the frames? Your garden seems to be very exposed. Does the snow drift?
    Do you have plants left outside?
    The coldest I have know is about 15F but some winters it does not snow. I have known 3ft of snow drifting to about 5ft. As it is rare for daytime temps. to stay below freezing the snow melts on the greenhouse. Snow equals disruption as I guess it is not economic to prepare for it.

  2. Hi Alain, Yes, I remove any significant snow from the top of the frames. We actually don't receive significant snow (greater than 10 inches) very often. All off my frost tender plants are now in the frames, or in the house. Of course my winter hardy cacti and succulents are in the garden and ready to handle the winter.

    I think our winters are similar to yours. In most years the lowest temperature is in the 5-10 degrees F. range (-12 to -15 C). Our average nightly low temperature in mid winter is 25 degrees F. (-4 C.). Our average yearly snowfall is 20 inches (50 cm) When I have my double layer of plastic on the frames I like to see snow on the plastic, it's an indication the insulating effects of the double plastic are working. If the snow is melting, it means the frames are losing heat through the plastic coverings. My problem with snow is causing trees to fall in the neighborhood and disrupting electric power transmission to my house. On several occasions in the past 10 years we have lost power for more than two days. At those times I've got to make certain the generator is running to keep the heaters in the frames working. Sacrifices to the hobby. :-)

    1. I think we get more dull days. I line the greenhouse with bubble plastic. Thankfully power cuts do not happen often. We only lost power for a few hours after our big storm in 1987. I know you have had worse.

  3. Your overwintering frames are fascinating. The results even more so! I do hope you have generators to keep -you- warm when the power goes out, too ;)

  4. Fascinating maybe, but an inexpensive way to get my plants through the winter. Retired teachers aren't so rich. Actually, I do have two generators, one for the plants and one for me. ;)

  5. I too use wooden/heavy plastic combo with burlap lined interiors. This will be my first winter trying to protect some agave in zone 8 your success has given me hope. Thanks

  6. You are welcome Craig. I hope your agaves come through the winter without damage. My biggest concern is a power outage during a very cold period. I do have a generator for backup electricity to run the heaters, but someone has to be present to run the generator. Thus, I stay pretty close to home in the winter. BTW the body of the frames is constructed with quarter inch plywood on the outside and inside of a 2x4" frame. There's a one inch thick piece of foam insulation between the two pieces of plywood. Most of the heat loss is through the plastic. As mentioned in the blog I add a second layer of plastic when temperatures drop below 25 degrees F. and a blanket between the two layers of plastic when temperatures drop below 20 degrees F.