Onion

At a glance

USDA Zones

3–9

Sun

Full sun (6+ hrs)

Water

Medium — water when top inch of soil is dry

Soil

Loam, sandy

pH

Neutral

Spacing

4 in. between plants

Per square foot

9 plants per square

Days to maturity

About 100 days

Planting & harvest windows

Northern Hemisphere timing. Adjust ±4–6 weeks based on your last/first frost dates.

Good companions

• 
  Tomato
• 
  Carrot

  Onion smell confuses the carrot fly; the strong scents mask each other's pest cues.

• 
  Lettuce
• 
  Strawberry

Keep apart from

• 
  Pea

  The onion family stunts the helpful root bacteria peas rely on, so they grow poorly.

• 
  Bush Bean

  The onion family stunts the helpful root bacteria beans rely on, cutting your harvest.

• 
  Sage

Recommended varieties

• Walla Walla Sweet

  110 daysstart

  Mild, juicy sweet onion. Best in long-day zones.

• Texas Sweet (Granex)

  100 daysstart

  Famous Vidalia-type — short-day, for southern beds.

• Red Burgundy

  100 daysstart

  Mild red onion, beautiful in salads.