Mnemonics

Day 78: How can you tell the difference between spruce and fir? That's a fairly common question around here, and something a simple mnemonic device can resolve. The needles of Spruce (starts with S) are square. Fir is flat (F). The images in the boxes show enlarged cross-sections of the needles, but you don't need to make a microscopic analysis. Simply try to roll a single needle between your thumb and forefinger. If it rolls easily (if somewhat bumpily), it's spruce. By virtue of being flat, fir needles won't roll. Wasn't that easy?