Actually, once they have started to change color, they’re not really photosynthesizing anymore. At least not enough to matter much. I think they’ll be just fine.

"And I'm not sure how thats the case when I see them in Canada in fall peak color while in Oregon, where its warmer is losing leaves sooner. I thought leaves drop first in colder areas."

You need to do some research on tree dormancy :-) Cold temps are not an overriding factor.....day length has an equal if not larger impact as does gradually declining temperatures. Oregon is further north than New Jersey so less daylight begins earlier there than it does further south. And
"warmer" is relative...........most of OR is milder than NJ in winter but it is not necessarily warmer than NJ overall. Rarely so in summer and with a pretty steady but gradual decline in both day time and night time temperatures starting in late summer. And this same gradual decline has not been duplicated by recent weather patterns along the east coast.

The peak of fall color in the PNW is almost always mid to late October and leaf drop follows very shortly thereafter. Most deciduous trees here have already lost all their leaves. And the deciduous conifers are among some of the earliest to shed their needles. My niece's grove of metasequoias are all fully naked :-) And I was at the nursery yesterday scoping out plants for a design project and noticed that the taxodiums and larches were all at least partially defoliated, if not fully defoliated, for the season.

with dormant plants.. i would be more concerned with accumulated heat in the package .... rather than light ...

but even 6 days of warmth.. should not cause it to break dormancy ...

ken

Strange that larch are so early coloring in the PNW. Where I live larches are among the very last to color and shed their needles. They are peak color right now, when almost all broadleaves are bare allready. There are yellow larches everywhere, they are surprisingly common for a non-native tree but you only noticing them now.

Well the 2 larches came in. The boxes had holes in them too which was good. One was 90% defoliated while the other still had 90% of its leaves on just starting to turn yellow. What is going on here? They were both raised in the same location but one is all shed and the other is just starting...

Btw, huggorm where are you? And is this larix kaempferi you are seeing or larix decidua?

One of them might have had more sun than the other, more water or nutrients, I wouldn't be too worried about it yet.

I'm in Scandinavia and I'm not sure what species of larch it is. Probably several, and of different subspecies, and also hybrids.

All red maples do not lose their leaves at the same time, even those that are growing in the same location. Nor do all dogwoods, katsuras, birches or just about any other deciduous tree you could name. Some of my Japanese maples still have most of their leaves....others dropped theirs weeks ago!! There is no reason to expect all larches would do otherwise.

Each plant is a unique individual entity and each will respond to both genetic/internal and exterior stimuli differently.