I'm not sure, but I think it likely acorns could sprout early in a greenhouse (light, warmth, moisture).

Redwoods grow in what's called "the fog belt" down in California and southern Oregon. They get a lot of rain in certain seasons, do not have to deal with very much deep cold, and seem to thrive in the natural fog.

But you should be able to go beyond what I can tell you (which isn't much). Have you tried the GW Trees forum? You'd probably find more expertise there. Good luck.

Joel

Why are you trying to sprout an acorn in a greenhouse???
Assuming you are trying to grow something native to PA or a similar location, the acorn probably needs stratification. I generally collect acorns in fall. and sort the noticably damaged ones out. Look for the small holes from insects mostly. Unfortunately squirrels get most of the good ones from a lot of trees. Next, remove the cap if loose and dip for about a minute in bleach water to kill fungus spores and such. then rinse and wrap in clean paper towels. Run water over the paper towel and wring out excess water. Then place in ziplock bag in fridge until spring. In spring, remove bag and check daily. If it is a good acorn and mold or fungus doesn't get it, it should sprout in several weeks. Chestnut oaks usually sprout in the fridge. Plant sprout in pot or desired location and protect from deer and squirrels. The "super size" cups from fast food places make good first pots, since they are deep for the tap roots.

Ziggy