Planting by the phase-of-the-moon (Rabbit-hole alert)

Lars Nordstrom in his book Making it Home has a very short bit of prose that sheds light on why many cultures swear by "planting-by-the-phase-of-the-moon".

Paraphrasing (because I no longer have a copy of the book):

Everybody in Scandinavia knows that the full moon brings frost.

There are countless times when people were fishing at night (quite possibly for capelin which spawn in fjords*, in the spring during the night) when the clouds parted to reveal a full moon. The temperature plummeted and frost immediately followed.

This seems like a clear case of cause-and-effect where the full-moon caused frost. It would only be logical to avoid planting tender plants when the moon is full, right? But let's dig just a little bit deeper.

Clearing skies

First, let's consider what kind of weather results cloudy skies becoming clear.

Typically, it would be a high-pressure dome displacing a low-pressure front. High pressure domes, in the springtime, are often cold, dry air.

Radiant heat losses

Clouds act like blankets that buffer temperature extremes. They reflect solar radiation back into space during the day. They reflect surface heat back toward the earth at night. Nights that are cloudy seldom experience the large, downward temperature change that occurs when the sky is clear.

Clear skies do not buffer temperatures that way. At night, temperatures plummet when there are no clouds because surface heat radiates outward as infrared radiation and there is nothing to reflect it back. That is why deserts are brutally hot during the day and (surprising many people) brutally cold at night.

Salience

When are night fisherman most likely to notice that the skies cleared? There is not much change to trigger an observation when the moon is not in the sky. It goes from dark to....still dark. No change there. Or would they be more likely to take notice and make a mental note when there is a full moon and the night goes from dark to much brighter very quickly?

So everybody knows...

So everybody knows that the full-moon brings killing frost because Great Uncle Ole  or Uncles Angus and Paddy were fishing in the shallows of the North Sea and saw with their very own eyes that the sudden appearance of the full moon in the middle of the night was  immediately followed by a heavy, killing frost.

The other cultural event when normally-sane people would not be snug-in-their beds at that time of year is if they have sheep and are lambing-on-pasture. That is, if they didn't keep the ewes confined in buildings while they were lambing. Different cultures have different lambing practices driven by predator levels and length of grazing season**.

In logical-debate the connection between the bright moon and frost is called a spurious association. Yes, it occurred. Yes, is not uncommon. But no, the presumed chain of cause-and-effect is flawed because the null hypothesis was not rigorously tested. How many nights did killing-frosts occur when the moon was new and a high-pressure dome displaced a low-pressure front in the middle-of-May? We don't know.

Everybody "knows" that full moons cause frost, that is, except for people from cultures that did not harvest capelin or lamb-on-pasture. They were snug in their beds when those spurious associations were happening.

Since the Schwertler Swabians that formed the nucleus of Copperhead Cove were not from Scandanavia, Scotland or Ireland or Denmark I decided to forego their "planting by the phase of the moon" because I did not want to be guilty of parroting information that may not have been universally followed by Appalachians who were not of Scots-Irish decent.

*A big tip-of-the-hat to Lucas Machias who called my attention to capelin as a possible resource that would be attractive to Scandinavians.

**The narrative of Jesus' birth as written in Luke suggests that Jesus might have been born in April based on when shepherds would be out at night with their flocks in the hills near Bethlehem. That time-frame was suggested because that is when locals timed the lambs to drop to maximize forage utilization.