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11 June 2016

Cold Death

Yay, spring!
is it possible to save a cold-damaged adenium?
Winter was not difficult, it was mild and late. That, however, came with a price--the worst, most unpredictable killing spring.

Most of my plants survived the winter in good shape but we kept getting dramatic and unexpected temperature plunges at night. I lost a few of my yearlings so I just ditched the obvious casualties. But then, two of my three-year old projects started looking none too pleased. They were growing back full heads of leaves but their trunks began to feel springy. Argh. Oedema. 

This is annoying. I've been working on these for three years. 

Oh alright, let's not dick around. By "working", I really mean they are part of an on-going experiment on growing hard specifically to achieve compact growth. Well okay, that's bullshit too. What it really means is that they have been grown very very very hard. Closer to the truth, it means they were rainfed and fertilized only when their leaves start yellowing. The rest of the time, they received no care at all. 

How to Spot Cold Damage on Adeniums
You know me, my first reaction is to always dig them out if there is nothing obviously wrong above the soil. Cold damage, however, often shows up above the soil fairly early; not so much on the leaves or branches (they will continue to look normal for a long time, in fact) but on the base of the plant. If you are not paying close attention, it may be too late by the time you discover it. 


The first sign is usually some wrinkling on the trunk of the plant. Adeniums with root rot will have a slightly sweet pungent odor but cold damaged ones will not. If you want to detect this problem even before the wrinkling happens, you can feel for it instead. 

When slightly squeezed, you'll notice an equally slight "give". A healthy adenium will be rock hard. A troubled one--either from cold damage, root rot or dehydration--will not.  Roots in crisis result in basically the same thing though--the plant will be dehydrated, hence the wrinkling.

The plant on the left has been in an advanced stage of the problem before I got around to digging it out. But at some point earlier I took this shot, the first time I noticed it. The discoloration right above the soil is not related, it was there from the crib. But that discoloration right below the first branch is new. You can tell from it that the plant has already died up to that point on the trunk.


Another one that looked relatively unharmed above the soil turned out more damaged. Both major roots were already very soft, closer to the feel of cucumber. Healthy adeniums should be very hard and solid, like fresh chilled carrots.

All that bendy root stuff is basically dead/dying tissue. There is no rot, as you can see below. That comes later. This is what happens when adenium in wet soil spends the night in temperatures below 10C. Some plants are even more sensitive and will do this at 15C below. As we can see, this happens to even healthy ones. When sliced, you will see the difference between root rot and cold damage. Cold damage looks definitely fatal (and it often is), but it will not have the pungent smell of bacterial or fungal rot that typically results from over-watering.

This one is probably a goner. But we will see.

The other one is a little better but still damaged. Note the crack on the fat root. Left in the pot, this would have gotten worse in under a week. It will be two to three more weeks before you see visible signs on the leaves themselves.

So, both plants were washed and cleaned. Another seedling, this one a yearling, was dug out and that had worse damage. The entire trunk from two centimeters above the soil all the way down to the roots, was mush.

The plan is to slice off the damaged part, allow them all to dry out and if they develop callouses at all, maybe plant them bank in the pot.  

If you ever have to do this, make sure you wash the plant very thoroughly. After that, trim the thinner roots close to the damaged area, just so you can see the section better.

If you have to do some surgery on cold-damaged plants, just follow the same procedure as grafting or pruning--use a clean and sharp cutter to remove all the damaged tissue. Make small, incremental cuts and keep cutting out until you see healthy plant tissue. Even a small speck of blemish can ultimately kill the left-over plant--that is dead tissue that will eventually rot. 

Sometimes there will be enough healthy plant material to actually make it possible to root the remaining portion. Sometimes, it won't be worth it. You can still see if the plant will callous over. Just don't expect a dramatic comeback. 

Some people will treat the cuts with various things like cinnamon, rooting hormone or what-not. I have long since done away with these treatments, failing to see any definite difference in the outcome. You should still do it, if it will make you feel better. I just don't know where I put my cinnamon stock and the rooting hormone is so far away. 

In any case, allowing the damaged plants to dry will also give you an idea of whether they will recover or not. The development of callouses is a good sign. That means the plant is still functioning somewhat. Often, however, cellular breakdown will just continue. If taken out of the pot and allowed to dry, a cold damaged plant will desiccate. 
What you want to do is to allow the cut to be covered by scar tissue. If that cut just dries out without callousing over, the chances of recovery is slim. 
In a normal, healthy plant, callousing over takes maybe two days. In summer, it can happen overnight. In a cold-damaged plant, this may take days to a week, with the added feature of rapid desiccation. Remember that since their roots have been damaged in the pot, they probably were already failing to take up water. Taking the plant out of pot only accelerates this. 

After a few days, these plants will be completely desiccated.
Such sad-looking things. I'm not optimistic.
There is really no hard and fast rule on when to put a cold-damaged plant back in the pot. I waited a week for this particular plant and then put it in gritty mix (i.e. no soil; just the 1:1:1 mix). 
Use the smallest pot you can fit them into. This way, they can be watered sparingly and the medium will still dry quickly. Over-potting these plants now will just soak them in moist medium, regardless of how fast-draining it is.
I'm a little more hopeful about this one on the left, it had significantly less damage although it still felt squishy and has remained squishy. It will have to grow new feeder roots before it can go full blast on taking up water and nutrients. It will not firm up until that happens. This is why there is less optimism for the other two plants above. They do not look like they have enough healthy tissue left to grow new roots. 

After a couple of months, you should already know whether the rescue is a success or not.  

UPDATE November 2016 

The worst affected remnant I tried to save above soldiered on for more than a couple of months though. Both tried to push new growth off and on, never quire sustaining the turn-around. As plants were being brought in for the winter, both plants finally kicked it. After digging them up for a post-mortem, it turned out both of them were living off of the energy stored in the cuttings themselves and neither developed roots. The one with the cracked root, however, recovered fully.

3 comments:

  1. Sorry to hear that. The spring was horrible indeed. I've lost one Adenium and another dropped the flower buds. And the cold rainy weather makes all other plants totally confused....

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    Replies
    1. Thanks, Rika. These were two of my healthiest, seed-grown plants too. It's hard to say what made them particularly susceptible, except I repotted them last August which I thought was enough time for them to recover, since they continued to grow well even through winter. Oh well. Que sera, sera.

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  2. A while back you said, "adenium sap all over my hands", so now I am happy to see the gloves. Melissa.

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