Echinopsis turning yellow

[grinel]

One of my E subdenudata is turning yellow at the moment, in a way I haven't seen before. It may be a gonner but I'm trying to understand why this happened and what causes it.
It's been kept in a shed with a window, at pretty high air humidity (80-95%), but dry substrate, since November last year, along with other hardy/semi-hardy cacti, and a few other E subdenudatas as well. It was then moved out in a plexiglas cold frame about 3 weeks ago and it seems that this is causing the yellowing to accelerate. It's been slowly creeping in over the last few months but it's definitely more pronounced since it was moved out. The cactus is firm to the touch, no soft spots so nothing to do with rot. It's just slowly losing chlorophyll.
All the other subdenudatas are looking fine, at first sight identical to what they looked like at the start of their dormancy.
Anyone seen something like this before?

[el48tel]

I have one doing similar plus black bits on top of growing point.
I think it might be cold plus moisture

[JonNo]

I experienced something similar to this with my current E. Subdenudata. It started to lose its shape, and then turned a strange sort of pastel yellow colour. I think I sought advice here, and was told I should check the roots and re-pot it. I did so, and it is still with me...

It has never entirely recovered its colour, where once it was the usual deep green colour all over only the top of the plant has now returned to that, the rest is still lighter and yellow-ish. But - since I re-potted it has flowered several times and now has a dozen or more offspring growing around the base. I may be wrong but I take this to mean the plant is reasonably happy!

So, I would conclude - don't worry too much! I would probably follow the same advice that I did, check the roots and re-pot it, and keep your fingers crossed. I guess I should qualify this by making it clear I am no sort of expert...

[grinel]

Thanks guys, I repotted it yesterday and will keep an eye on it.

[habanerocat]

From personal experience, in both those photos above, I'd put it down to too alkaline a compost and/or inconsistent feeding.
The dark yellow patches on the first one indicates some cold damage to me also.

[grinel]

The dark yellow spots are glossy and look like I could peel them off with my fingernail, but I haven't tried. The temperature in the shed went down to -1 for a couple nights only, the rest of the time stayed on the positive side. The info I found on this species is that it can withstand down to -7, don't know how accurate that is though..

It was bought from Ikea, came in peat, and it was moved to a 50-50 JI and grit, so maybe it didn't appreciate the change. I don't think I've fed it more than once or twice last year, so that may also be the cause.

I'm curious to see if it makes a comeback, but it's gonna be at least two more weeks till the first watering of the season, so it needs to hang in there.

[JonNo]

From personal experience, in both those photos above, I'd put it down to too alkaline a compost and/or inconsistent feeding.
The dark yellow patches on the first one indicates some cold damage to me also.

Interesting observations and food for thought (if you'll pardon the pun). My plant is also in John Innes, a simple mixture of JI no.2 and RHS horticultural grit. It gets fed regularly with Chempak cactus and succulent fertilizer throughout most of the "watering period" each year. Aside from the slightly odd colouring it now seems mostly happy with its lot...

Two other notions that have occurred to me are 1) it may be some sort of skin reaction to the various potions (like Bug Clear Ultra) it gets sprayed with regularly in the battle against Mealys?; and 2) it may be some sort of "sun bleaching" - my plant is a house plant that lives on a South facing window sill, where the sun can sometimes be really quite fierce (even today it turned one side of my Polaskia Chichipe bright red!)?

Good luck with it grinel.

[grinel]

Thanks JonNo - mine is definitely not sun bleached, it started getting yellow during the cold season. Probably the lack of fertilizer is what caused my issue, I remember it bloomed twice after I moved it to the JI mix and probably exhausted itself.
Thanks for your thoughts guys, I'm curious to see if this is reversible, I'll confirm in a few months one way or the other.

[esp]

The dark yellow spots are glossy and look like I could peel them off with my fingernail, but I haven't tried. The temperature in the shed went down to -1 for a couple nights only, the rest of the time stayed on the positive side. The info I found on this species is that it can withstand down to -7, don't know how accurate that is though..

It looks like cold damage to me. British winters are relatively challenging for many cacti. In addition to the minimum temperatures, low daytime maximum temps can give spells of prolonged low temperatures, with high humidity and lack of sunlight to compound the difficulties. In contrast, many cactus habitats have warm daytime temperatures and a lot of winter sun, even if overnight temps may dip briefly below freezing.
E. subdenudata isn't an especially high altitude species, I'd be surprised if many populations of it get much below freezing in habitat. Llifle give it -7C, I think this may be rather optimistic. It only states -5C for many Rebutias and Lobivias, for example, which are likely to get rather colder minima than this species.

[el48tel]

The dark yellow spots are glossy and look like I could peel them off with my fingernail, but I haven't tried. The temperature in the shed went down to -1 for a couple nights only, the rest of the time stayed on the positive side. The info I found on this species is that it can withstand down to -7, don't know how accurate that is though..

It looks like cold damage to me. British winters are relatively challenging for many cacti. In addition to the minimum temperatures, low daytime maximum temps can give spells of prolonged low temperatures, with high humidity and lack of sunlight to compound the difficulties. In contrast, many cactus habitats have warm daytime temperatures and a lot of winter sun, even if overnight temps may dip briefly below freezing.
E. subdenudata isn't an especially high altitude species, I'd be surprised if many populations of it get much below freezing in habitat. Llifle give it -7C, I think this may be rather optimistic. It only states -5C for many Rebutias and Lobivias, for example, which are likely to get rather colder minima than this species.

I agree. And I think it's the combination ... mainly cold AND damp.