where are you???

how do you imagine.. that feeding a plant.. will change its genetic ability to withstand cold???

have you had a soil test done.. to understand.. what if any soil supplements are needed ...???

and the final thought... how many times do you need to fail.. to understand.. that its probably not going to work.. in your micro climate ...?? ... and trust me.. i have tried to beat ma nature many times... and i have never won ... maybe for a few years.. but the odds are heavily stacked in her favor ... for the long term ...

it really doesnt matter.. what success.. others have had.. one town over... its apparently a different microclimate ... for whatever reason.. ma nature decides ... perhaps winter wind .. who knows ...

keep trying.. until you give up ... been there.. done that ...

ken

ps: i never fert transplants.. until they are re-established.. and on a large transplant.. that could be a few years ... obviously.. a little of this or that is rarely going to hurt ... but if its that little.. what difference will it make.. ???

Agreed on all points. But maybe I enjoy heartbreak I don't know.
I'm open to giving anything a shot Ken. If one takes for a couple seasons, mission accomplished!
I think potassium is beneficial for hardening off. But unsure to what extent.
I think while milder here, the higher elevation survivors may have less winter winds. All assumption there.

My first though is no fertilizer or anything that will promote abnormal growth. Especially late in the summer. Oh, and beware the lawn fertilizers if u use them.

There is a chance your neighbors just got lucky with a few warm winters that allowed theirs to get estsblished.

What to do would be buy en masse and experiment. Some get nothing, some this some that.

Based on the distribution of Sequoiadendron in eastern North America, winter root zone temperatures are a huge factor when grown in zones 5 and 6. They seem to perform in zones 5 & 6 the best when they can benefit from:
- traditional snowbelt areas in the lee of the Great Lakes
- deep sandy (quick draining) soils
- short duration cold snaps

Does the higher elevation town near you get more reliable snow cover?

At the least, there is some justification for thinking some potash may be beneficial, in that, as OP says, it is associated with plant cell turgor, hardening-off, and resistance to a variety of stressors. All that said, if I had to guess, I'd say it's not going to work, other factors easily overwhelming any small change that might be possible with the K fertilizer. But that's just my guess.

+oM

Agree with last post.

It is well-known that *healthy* plants are better able to withstand heat / cold / pests, et cetera, within reasonable limits, of course. If supplying a nutrient will increase the overall vitality, it will theoretically help as much as possible.

Josh