Silver fir

Its cones disintegrate right on the tree — you never find a whole fir cone on the ground. The simplest test, valid all year round on any needle: roll it between two fingers. The fir's is flat and does not roll; the spruce's is almost square in cross-section and rolls easily. Another reliable marker: the scar left on the shoot after a needle falls — a small, smooth round sucker-like scar on the fir, a small woody peg that makes the shoot rough on the spruce. Finally, if cones are present: those of the fir stay upright and disintegrate on the tree, those of the spruce hang head down and fall whole.