Lobivia arachnacantha not cold tolerant?

[Nick_G]

In Tomasz Blaczkowski's recent Lobivia booklet he describes Lobivia arachnacantha as 'sensitive to cold,not resistant to frost, even small frosts can kill this Lobivia'. Really? Has anyone experienced this? Does he mean possibly just the species and not the varieties. My vallegrandensis, sulphurea and densiseta have all experienced greenhouse temperatures down to -6C and come through totally unscathed. I only obtained a couple of plants of var.arachnacantha in 2019 and we haven't had any really chilly weather here since then. Tonight promises -6 to -8C apparently so maybe I should bring one inside.

[iann]

Most publications are comically conservative about how much frost a cactus can take. I have a highly-regarded book which says Pediocactus must stay above a minimum winter temperature of 7C, but I'd be surprised if most Pediocactus would grow if they never went below 7C. Often I wonder if they've killed a plant at, say, 5C, so they think that's as cold as it can ever go. Then there's that tricky zone where a plant might survive a temperature only very briefly, or might survive but lose its roots, mark up, or be set back in its growth. Still, most "official" sources appear to me to be hopelessly inaccurate on the subject. Perhaps they're just trying to cover themselves in case of loss.

Anyway, your Lobivia should be pretty safe at least -5C, probably lower. Not sure about all those varieties.

[Nick_G]

I don't think that's the case here Ian, he's saying that arachnacantha is the exception and that it won't tolerate low temperatures like other Lobivias. Mind you, Essex cold isn't quite the same as Poland cold.

[Paul in Essex]

I'd wait until after tonight before making such rash statements

[esp]

He's made at least one collection of this species:

Field number : TB 814.1
Collector : Tomasz Blaczkowski
Species : Lobivia arachnacantha
Locality : Bolivia : Santa Cruz (Samaipata, 1880 m)
Date : 2014/01/21

From Wikipedia, in Samaipata, "Frost occurs on nine days in an average year", presumably normally mild and of hours rather than days duration.

It's certainly not the highest location this plant has been found at, so Thomasz's collection may be a bit less cold tolerant than some, but you'd expect at least a teeny hint of frost tolerance. Maybe don't risk >=-6C unless you've got seedlings to spare?

[iann]

I'd wait until after tonight before making such rash statements

I might have the heater on tonight, Phil. Only forecast for about -5C, but I still have lots of stuff out that I'd only consider lightly frost-hardy. The Pediocactus have been watered so I'm all up for freezing nights and sunny days.

[ralphrmartin]

My L. arachnacanthas were previously kept at 5C, and now are in the unheated part of the greenhouse, and they seem fine. I can't say I have deliberately frozen any, but they don't show any marks I would associate with cold damage.

[Ali Baba]

I'd wait until after tonight before making such rash statements

South Benfleet-3C, Kracow -11C tonight according to the Beeb

[MatDz]

I'd wait until after tonight before making such rash statements

South Benfleet-3C, Kracow -11C tonight according to the Beeb

And it's like that for the past week or so, and will be for 2-ish weeks. Months with constant subzero temperatures are not that uncommon as well

[Paul in Essex]

Yet another attempt at humour falls flat.