Hardy cacti seedlings unprotected from winter frost; a good idea?

[Aiko]

Earlier this year I have sown a lot of hardy cacti, such as Mammillaria lasiacantha, Coryphantha echinus and quite a few Echinomastus, Echinofossulocactus and Ancistrocactus species.

They are pretty plants and as they are quite hardy they save me the bother to shelter them from the cold in winter. I can just keep them in my unheated greenhouse during the winter. It hardly gets colder than -10C, just an occasional night. And on even more occasional nights it might get colder than this, but then I can just take them inside for a night or two.

All fine for adult plants. But I was wondering if it would be a good idea to keep my one year old and zero year old seedlings in the greenhouse during winter. Being so young and tiny, would they also be able to withstand the cold as easily as the more mature plants? I would hate to lose them already.

Anyone with experience on hardy cacti seedlings and winter frost?

[7george]

It is not easy to say this from distance, hardiness depends on the clone you work with and other things. Sometimes I keep my hardy seedlings indoors first winter(s). The survival rate for those left in the cold might be lower. If you have several pots or trays from the same kind better bring some indoors. If seedlings are really tiny I would be concerned not to dry them out and watering in cold greenhouse seems risky because of unpredictable temperature drops.

[DaveW]

Keeping them drier in a greenhouse is a help since our winters in this part of Europe are much wetter than habitat if outside when cold. A lot of small seedlings grow under nurse plants or rocks at first in habitat so live in a warmer microclimate than when mature, therefore can be more susceptible to cold than when mature. A layer of newspaper over plants in a cold greenhouse on very cold periods works wonders. If dormant they should not etiolate.

[Andrzej1972]

A bit old topic, but I'll throw in a sentence. Even this year's seedlings left for the winter, such as Escobaria missouriensis, Gymno. baladinum, E. micromeris, opuntias, echinocereus, itp. survive the winter (UK) by eye - without losses. When I try to winter them at home, it is much worse. Sometimes out of 50 planted survives 5-6. So the ones I know are hardy I prefer to keep outside. I dont know why, maybe fresh air doing Good?