Help for newbie to identify a possible problem

[el48tel]

My Grusonii has developed these brown patches during the 3 winter months in the greenhouse at 6C.
1. what might they be?
2. is it curable?
3. will it recover?

[topsy]

Hello,

This has been caused by a combination of cold and damp. This particular species is prone to getting these orange spots. They will not go away. However if you continue to grow your cactus and keep it warmer next winter, perhaps indoors until it gets larger, the epidermis will move down the plant and the spots not be so noticeable. The other option you have, as this is a freely available species is to buy another one.

So a warmer and drier atmosphere is the answer for next winter.

Good luck, Suzanne

[SpikyMike]

I’m wondering if it is due to a mite called Brevipalpus russula. These are tiny. Far too small to see with a naked eye. I have seen some of them on some of my plants bothusing a 30x loupe magnifier (£4 via eBay). I’m using weekly applications of neem oil spray as apparently these little beasties ingest the neem and it causes them to fail to reproduce or something.

[Diane]

I agree with Topsy- it looks typical of cold damage.

[el48tel]

Thanks guys
The cold n damp seems to fit the diagnosis.
As for replacement ... no can do ... it was a gift from daughter. So it's warm TLC and wait.

[Cidermanrolls]

I’d check your thermometer.
Mine lives at 5 or so in winter and doesn’t get so marked.

[Ali Baba]

I’d check your thermometer.
Mine lives at 5 or so in winter and doesn’t get so marked.

You took the words out of my mouth, mine is kept at around 6C and has never marked.

[ragamala]

I have one Echinocactus grusonii of the yellow-spined variety that has survived forty years with me and has lived in an unheated greenhouse (where for sure temperatures have gone well below 5 or 6 degrees) and survived without marking. It may well be that younger plants are more susceptible to cold damage, mine got treated "better" when they were young and experienced later survival of the fittest neglect.

[habanerocat]

Looks like cold damage to me also.

I'm a firm believer that cold hardiness can vary a lot from plant to plant. Call it variety, sub-species or whatever you want. Some plants survive the cold better than others.

Any plant I ever brought back from Spain has died, whereas plants from continental Europe and seed I've grown myself all seem hardier.

Perhaps it's the DNA of the seeds or perhaps the way they are treated the first few years. I don't know.
It's just what I have found from experience. Perhaps because I grow them hard (very little water and fertilizer). I just don't know.

[RAYWOODBRIDGE]

This species will take a few degrees of frost no problem, but as Suzanne says it is the damp with the cold that marks this plant.

In habitat this plant goes down to -10c ( 14f ) with no problems but the air will be very dry, so far this winter my plants of this species have gone down to -4c and they are fine, Ferocactus also mark up badly if the humidity is high on a cold night.

Growing your own plants from seeds will always give you a plant that has survived your conditions as a seedling therefore more at home in your growing conditions, while many of the others in the same seed pan will have died off as you say habanerocat it is just the variety within the seed of the species