Dried up suddenly

[lebmung]

I have a kaffir lime around 5 years old in a 15 l pot,  around 1.2 m canopy.
I found it today dried up suddenly, few days ago it was okay.
It's in a cold room where my citrus stays dormant at around 4-8 C. Another similar kaffir does ok. So they did many of the previous years.
Rootstock is Ichang papeda, which is good rootstock for kf.
Last few days there was a lot of sunshine after a month without sun. Maybe this influenced.
It's intriguing to me what happened. The tree dried with the leaves not dropping but they just dried up all of them.
I cut back the tree and hope to recover it.  Though I don't give it many chances. Usually if there is a root problem the leaves start to yellow and drop. Any ideas?

[Laaz]

Probably salt build up. Try re-potting, spraying the roots clean of the old & replanting in a fresh new soil.

[lebmung]

Probably salt build up. Try re-potting, spraying the roots clean of the old & replanting in a fresh new soil.

Still winter and cold to do that. Yes the pot is filled with roots. I need to do it in spring if it still survives. I cut back to to the main stem all the fried leaves and twigs. I also drenched with a dilute peroxide solution to increase the oxygen level in the roots.

[Millet]

The cause of this quick decline has to be in the roots.  I would slip the tree from the container and examine the root system.

[citrange]

I also aim to keep my greenhouse at around 3C to 8C over winter.
Theoretically this means the potted citrus are dormant and require very little water.
But, even here in England in January, the sun does come out.
It only takes half an hour of sun and the temperature passes 10C (50F).
Today, for instance, it has been just above freezing outside but the sun shone all day and the greenhouse reached 22C (72F)
That means the plants immediately use a considerable amount of water.
If they don't get any water they rapidly dry out and the leaves curl and I find a whole plant can rapidly die - particularly in the smaller pots. So it is a constant battle between leaving them cold and damp, or too dry.
I guess your Citrus hystrix needed watering!

[lebmung]

The cause of this quick decline has to be in the roots.  I would slip the tree from the container and examine the root system.

True the tree is root bound and a sudden increase in temperature lead to drying. So far it seems to do oky after cutting back all branches. The thing with ishang papeda as a root stock, it starts to lose leaves with the cold weather, but never experienced a sudden death.

[lebmung]

I found why the tree died. An accidental  use of potassium phosphonate which in highly mobile within the plant killed it.
While very useful at correct dose, just a little bit too much and trees die. I was treating avocado trees and some left over pour it into this kaffir lime.