Wintering

[ossy96]

Hello cacti collectors,
I would like to make my cacti bloom and because of that i put them in an unfinished, unheated house where the temperature drops even around - 1°C and The humidity is around 70 % Last time i measured... (which is very high for cacti) what can i do to make them not die in Winter?
Sorry for my english

[Aiko]

Open the windows on nights when the temperature does not go down much than around -2C or so. Then all cacti should be alright as most can handle a bit of frost (assuming you don't have specific heath lovers). Fresh air will be one of the best things you can provide for your plants year round.

What do you mean with an 'unfinished greenhouse'?

[ossy96]

@Aiko its not a greenhouse, its a house made out of bricks, but i have plenty of sunlight, its just unfinished and cold...

[Nino_G]

Aiko's advice is good. In my experience low temperatures and high relative humidity are not a problem if sufficient ventilation (air flow) is available. I overwinter my cacti on an open balcony where temperatures regularly drop below zero and plants often experience morning fogs (relative humidity 100%) at the same time. I've been doing it for over 30 years and never had any problems with the plants. I do not keep sub-tropical or tropical species, though.
Maybe you can post a list of the cacti you're growing?

[ossy96]

Well there i have species like: echinopsis oxygona, opuntia moncantha, Lobivia subdenudata, ferocactus emoryi, other ferocactus species, stenocereus pruinosus, parodia magnifica etc
.

[gillinger]

FWIW, whereas most of my collection is in an unheated (though fleece-lined greenhouse) I keep all my Ferocacti, S. pruinosis and P. magnifica indoors in a cool room. https://www.llifle.com/Encyclopedia/CACTI/ is a good place to find out tolerance to cold for each variety.

[Nino_G]

Well there i have species like: echinopsis oxygona, opuntia moncantha, Lobivia subdenudata, ferocactus emoryi, other ferocactus species, stenocereus pruinosus, parodia magnifica etc.

None of the listed species will have problems with mild frost, so I wouldn't worry about that. Just provide sufficient ventilation and light, and everything should be OK.
P.S. It would help if you would specify your location (please note that most members have location specified in their profiles) for better understanding of climate conditions in your area.

[ossy96]

@Nino_G i updated it

[ossy96]

Update species: Pilosocereus pachycladus, pachycereus pringlei, Cephalocereus senilis, astrophytum myriostigma, astrophytum ornatum, opuntia microdasys,