Onion Day Length

How to Choose the Right Onion Varieties

Onion Daylength Map

Long-Day: Northern States

  • Suited for latitudes of 37–47°
  • Initiate bulbing process when daylength is 14–16 hours
  • Usually better for long storage

Intermediate-Day: Middle States

  • Suited for latitudes of 32–42°
  • Initiate bulbing process when daylength is 12–14 hours
  • Produces onions of reasonable size except Southernmost Florida and Texas
  • Usually very sweet

Short-Day: Southern States

  • Suited for latitudes of 25–35°
  • Initiate bulbing process when daylength is 10–12 hours
  • Plant earlier for larger results

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