Worm Moon

The usual explanation is earthworm casts appearing in softening soil, and there is a complication worth knowing: across the formerly glaciated north there are no native earthworms at all. The ice removed them, and the worms found there today are European species introduced after contact — arriving well after the period the name supposedly describes.

The older record is more specific, and it is not about soil at all. Captain Jonathan Carver, travelling among the Dakota in 1766 and 1767, wrote that March was called the Worm Month or Moon “because at this time the worms quit their retreats in the bark of the trees, wood, &c. where they have sheltered themselves during the winter.” Carver’s “worms” are usually identified today as beetle larvae; the part that matters is that they come out of wood rather than out of the ground. His account was published in 1778, a century and a half before the almanac list that made the name famous.

The alternatives are more literal about the season. Sap Moon and Sugar Moon mark the tapping of sugar maples, which runs when nights still freeze but days thaw. Crust Moon describes snow that melts by day and refreezes overnight into a walkable crust. Crow Moon notes the return of cawing as winter breaks.

The March full moon carries ecclesiastical weight too. The Paschal Moon — the first full moon on or after the vernal equinox — determines the date of Easter, which falls on the following Sunday. The church uses a calculated approximation rather than the true astronomical moon, so the two occasionally disagree by a day.

Also known as

• Crow Moon
• Sap Moon
• Sugar Moon
• Lenten Moon
• Crust Moon

The 1778 record

Travelling among the Dakota in 1766 and 1767, Captain Jonathan Carver wrote down all twelve month names in a single passage. Published in 1778, it predates the almanac list by roughly a century and a half and is the oldest independent check on these names.