Light levels needed for cacti over winter

[gerald]

As the start of winter is approaching I am in two minds as to how to treat my cacti. The simple way would be to just leave them in the greenhouse, bubblewrap for insulation etc but the problem as always is it's not easy - or cheap - to regulate temperature and dampness.

The alternative is to keep them in a spare, unheated room in the house. I only have 100 or plants and none are large, so they are easily moved and can be stacked on shelves on the wall opposite the window. Indoors the temperature and humidity will be easier and cheaper to regulate, but there is just one window and it's west facing. So my question is, do cacti need much light during their dormant period, even if they're not actively growing? If not, then I could actually just stack them up in trays so they're pretty much in the dark, or is this inadvisable? Comments welcome!

[Phil_SK]

Indoors is the winner - I only stopped doing it when I reached the point where I had too many plants and they were getting too heavy. If they are dormant they need no light whatsoever. Before I moved here I had no spare bedroom space and overwintered them in a windowless cellar. The only plants that didn't like this were things like Agave, Haworthia, Echeveria. The cacti were fine. In a bedroom, those three non-cacti were much happier. Keep an eye on any Cleistocactus - if they get too dehydrated (hard to predict - dependent on plant size/watering/temperature) they can lose the growing point, so I use to give them a dribble of water in January. Don't be tempted to give them any heating when it gets really cold - what feels cold to us isn't really cold and if they're too warm for too long more will start to suffer from dehydration.

[Conrad]

Sorry if this is hijacking your thread a little Gerald, but I've been thinking about this too. My issue is that the room I plan on keeping them in isn't that cold since it's above a living room which often has an open fire. Is there a danger that if temperatures get a little too high then plants will come out of dormancy and start producing horrible etiolated growth, even if totally dehydrated?

How warm is too warm over winter indoors?

Thanks, Conrad.

[Ross M]

Ideally, I guess you're looking to keep them around 5-10C indoors. If it rises above 15C for some time, they'll likely want to start growing.

My plants, whilst kept in a greenhouse all year, receive no sun at all from October to March and don't seem to mind. Doesn't help with the heating bills 'though

[gerald]

If they are dormant they need no light whatsoever.

This is pretty much what I thought but wanted some kind of confirmation.

I think I'll keep them in the greenhouse until December, by then they should be dormant. Then indoors until the end of Feb. I'm guessing that even if they aren't 100% dormant during any or part of this time, the growth will be so slow that etiolation will be minimal. That I won't have to heat the greenhouse for the three coldest months which will save a few £££.

[delandmo]

Hi Gerald,

All the advice so far has been spot on. But remember the plants will only go into dormancy once watering has ceased. This will be the end of Sept / early Oct, depending on the weather. If you intend to leave them in the greenhouse until December, you will have to keep up to date with the weather forecasts, as we have had heavy snowfalls and frosts in November in recent years. Although, last year was the hottest November for some time and prompted an abnormal show of flowers from my cacti.Watering had ceased in late Sept. and were supposedly dormant ! Just as an added safeguard you can cover them with newspapers whilst still in the greenhouse in the later months. My greenhouse is heated to 5 degrees when needed. Derek.

[rodsmith]

My plants, whilst kept in a greenhouse all year, receive no sun at all from October to March and don't seem to mind. Doesn't help with the heating bills 'though

Hi Gerald,

All the advice so far has been spot on.... My greenhouse is heated to 5 degrees when needed. Derek.

Similar to Ross, my greenhouse gets no sun from mid October to late February, although it is in a bright position and not overhung by trees. Humidity is also pretty high in this part of the country and like delandmo I heat my greenhouse to around 5 degrees C. I have had very few fatalities over the past two years (since I've had the greenhouse). I stop watering pretty well at the end of September to ensure maximum drying out and growth cessation before the cold weather comes. The "darkened room" method is one I've heard about before and seems to work with most cacti. I would be careful with succulents though. Conophytums, especially, are in growth in the winter and need plenty of light and some water.

[topsy]

Hi Gerald,

I do wonder just how much heat some of our cacti really need. We were contacted three weeks ago by a 90 years old gentleman in Surrey who wished to find new homes for his treasures as he could no longer cope with them due to arthritis. We had been in contact before and bought his Melocactus plants. All his plants were kept in cold frames throughout the summer and he used to take indoors the more tender plants. We wondered just how many plants he had remaining as we remembered some very nice, ancient Ferocacti, but couldn't remember what else was there.

These remaining plants were kept in the cold frames all year round without heating:
Ferocactus (many species), Lophophora, Trichocereus, Echinocereus (many species), Escobaria leei, Notocactus roseoluteus, Lithops lesliei venteri, a Drosanthemum, Rebutia heliosa, Mammillaria plumosa had succumbed in parts, Oreocereus, Leuchtenbergia in full flower plus a few others. Most of the plants were in clay pots.

Four of the frames were raised up to waist height and the fifth was standing on paving slabs. There were no mealy bugs, most of the plants could have been put straight on the show bench, the only problem was weeds such as Oxalis and perhaps the odd snail.

So this begs the question - do we molly coddle our plants?

Regards, Suzanne Mace
Mesemb Study Group

[cactusrogerUK]

So this begs the question - do we molly coddle our plants?

I was chatting with Rene Geissler last year and was surprised when he told me he keep his plants (apart from the ones he knows need warmth) at a minimum of 2 degrees C.

[Mike P]

Likewise I heat to just exclude frost and for the hardy plants get no heating at all. It means a short growing season in the unheated house as watering has already stopped and won't resume until April.