Hmmm...don't know what osmotic stress is.
Basically osmotic stress occurs when a high concentration of ’salts’ is outside the root cells, lowering the concentration of water there. The roots cells contain a higher concentration of water. When the difference between the root cells and outside is becomes too great, the water in the roots flows outside to try to compensate the water inbalance.
This phenomenon weakens or interrupts the water flow up the tree. The needles are furthest from the roots, so these are affected first… causing the needles to wilt.
This is the main reason folks are told to water soon before fertilizing. This hydrates the area around the roots so when fertilizer arrives there will be less of a difference between the concentration of water inside the root cells and outside.
Another time this situation frequently occurs is when one fertilizes a tree in the weeks after major root work.
As I said above, a bunch of my Larches got frost burned early in the spring and have been struggling since. I don't think this would have happened if the spring burn wouldn't have happened to begin with.
Highly likely. Its also highly likely the roots were frozen and damaged. This would explain why the tree was not robust afterwards..
. I see wild larch get frost bit at the apex up in the forests all the time in the spring, but they just re-grow the needles and take off again.
In this case the roots are insulated by the ground. Only the needles are affected. Thus the tree has working roots, so the energy stored in the tree is able to be used to activate new buds.
Is this the same larch we have out here (larix laricina)?
It’s Western Larch.
Larix occidentalis
I'm no expert but here's my take based on what I've seen with my collected larches. If the tree that collapsed has not yet formed terminal buds it is probably a goner.
Very likely ….unless the roots could uptake enough water to make the needles turgid soon. Misting may help.
If it does have buds then I think your best bet is to focus on getting it through the winter to next spring, and then treat it as you would a newly collected tree with minimal roots (shade, mist, etc.). That would mean focusing on fall dormancy right now, not trying to trigger new growth. I recall fall dormancy for larches is based on reduced photoperiod so an extreme appraoch would be to move it to a dark space for a month or so. Around here the leaf drop trigger is in September.
Both photoperiod and temperature are triggers. Yet it takes a number of weeks/months to achieve full dormancy.
But yeah, I'm no expert...
None of us are, we are all learners.
cheers
DSD sends