Do Cacti NEED light in Winter!

Hi all,

My brother has almost run out of room for his cacti and succulent collection in his small greenhouse - and I will most likely also be faced with the same dilemma in a few years!

A very simple - and probably silly question: Do Cacti NEED light in Winter as they are dormant (most of them)... I asked members of my local Branch and no one could categorically say if they do. The question is asked because he does have room in his windowless garage!

I wonder if any members here could say with a degree of informed knowledge/confidence whether they would survive ok or suffer/be damaged in anyway. The temperature would be ok and they can be checked regularly - just missing the light!

I have put aside a small tray of not so precious plants and will put them in my garage to try this Winter if I have no responses

Thanks, Bill

Hi Bill,
This is a good question, and not something that I have seen a firm answer. I can only go on my own experiences, and two in particular.
I had a Belgian friend who brought his cacti (all Mammillarias) into his house over the winter simply because he could not afford heating costs. He had a spare room with a window which faced west, I think. He didn't heat this room but it gained some heat and remained frost free from the surrounding rooms. He made sure that he stopped watering quite early, so that growth had ended by the time he brought them inside. His plants survived and didn't appear to suffer.
The second is closer to home. We moved house 4 years ago, actually today, as it so happens. I bought second hand supermarket stacking crates and packed all my 1800 plants into them. Our new house had no greenhouse, so the crates went into the garage exactly as they had been transported - stacked up to 5 high, with taller plants (such as M. angelensis, dioica and other Baja species) on the top. The garage was a large double garage with tiled roof, so quite a large volume. I put one 3kw heater on, with a 5C thermostat, and left them all winter, until the following late March, by which tie the new greenhouse was erected, staging built and electrics installed. I then unpacked the crates, and worried that having been kept in relatively dark conditions all winter that some plants might scorch. With so many plants I couldn't really shade some and not others. I do expect to lose a few plants over winter, but inn fact I lost very few, and I had good flowering on many of the species. I had worried that this might be impacted, as I had always believed that winter light was needed to help the formation of flower buds inside the plant body. But it didn;t seem to be.
So a couple of stories, no real conclusion, though I believe that in cold countries like Canada plants always overwinter inside.

I have heard stories that long ago, when we still had cold winters in the Netherlands, there were cactophiles that wrapped their cacti in newspaper and put them in a cellar or a cabinet, i.e. a cool, dark place. That seemed to work well and so, there should be no problem in what your brother is planning to do. The idea was that in winter the plants don't grow and therefore they don't need light. It should work for most cacti, except for a few like M. senilis and M. rubrograndis who seem to profit from light in the winter (better flowering). But these two don't mind a few degrees of frost, so you can leave those in your greenhouse.
A garage seems an excellent place for your, and your brother's, purpose.

Another solution to the problem is to buy a larger greenhouse, for otherwise the overwintering problem becomes bigger every year .

Wolter ten Hoeve.

Thanks very much for that convincing feedback guys. Very much appreciated and sounds likely to be very much ok. I'm sure my brother will try that and I'm going to do my own trial out of interest

Cheers, Bill

When I still lived in Austria I used to live in an apt. and had my cacti on the balcony, which obviously brought up the question what to do with them in winter. Before the first frost I let the substrate try out completely, unpotted the plants, wrapped them in paper and stored them at cellar temperature (around 5-10°C in boxes. Then after the last frost I potted tem again and proceeded as usual. As far as I remember, I never had any casualties over the winter.
The only downside was that it's a lot of work to unpot/pot all the plants every year.