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What causes fret sprout in winter?

Fret sprout is what happens when your fretboard shrinks and your frets, being metal, absolutely do not. Suddenly those fret ends that used to sit flush against the neck edge are poking out just enough to slice up your hand every time you slide up and down the neck. Annoying, common, and almost always a humidity problem — not some manufacturing defect you can blame the factory for.

Why winter specifically

Winter heating dries out indoor air, often dropping well below the 40–60% relative humidity range wood actually wants to live in. Your fretboard — usually a thin, exposed piece of wood — loses moisture and shrinks slightly across its width. The frets don't shrink one bit. Result: fret ends that used to be flush are now sticking out past the wood like tiny metal splinters.

Is it permanent?

Not necessarily. If the shrinkage is moderate and you get the guitar back into a healthy humidity range, the wood can regain some of that lost moisture, and the sprout can improve — sometimes a lot. If it's been dry for a long stretch, or the wood has shrunk enough to leave a permanent gap, the fret ends may need a proper dress (filed flush) to actually fix it.

The actual fix, long term

Humidify. A case humidifier during dry months, kept in that 40–60% range, stops this from happening in the first place. If it's already sprouted, get the guitar humidified back to a healthy range first — sometimes that alone solves it. Sharp fret ends still there after that? A fret dress handles the rest.

Sharp frets aren't just annoying — they're a warning label. If you're seeing sprout, your guitar is telling you it's too dry, and other parts of the instrument are feeling that same stress, even if they're being quieter about it.