Zone 11 · Alliums Growing Guide

When to Plant Onion
in Zone 11

Plant from seeds (start very early), sets, or transplants. Choose varieties for your day-length: long-day onions for zones 5+, short-day for zones 7 and south. Day-length matters more than anything.

Plant outdoors
Oct – Dec
Start indoors
Direct sow
Last Frost
~none
Days to harvest
90–120 days
Difficulty
Medium
Wrong season — Zone 11
Harvest window: Jan – Mar

Planting Calendar

In Zone 11, Onion should be planted outdoors Oct – Dec, after the average last frost date of approximately none.

Short-day varieties. Cool season planting only.

Care Guide

Sunlight
Full sun · 6–8 hrs/day
Watering
Moderate
Spacing
4–6 inches
Soil
Loose, well-draining, fertile
Days to maturity
90–120 days
Soil pH
6.0–7.0
plant tip · Zone 11

Short-day varieties. Cool season planting only.

Feeding Schedule

How often
monthly
Feed type
high nitrogen then high potassium
Key timing
switch to high-potassium 6 weeks before harvest

Feed nitrogen monthly until bulbs start to form, then switch to high-potassium feed to encourage bulb sizing.

Companion Planting for Onion

What you plant next to onion makes a real difference — some plants actively help, others compete or attract pests.

Grows well with
  • Carrots
  • Brassicas
  • Tomatoes
  • Beets
Keep away from
  • Beans
  • Peas
  • Asparagus

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Common questions

In Zone 11, onion is a fall-planted crop. Plant outdoors Oct – Dec once temperatures cool in autumn. It overwinters and is ready to harvest around Jan – Mar. No last frost consideration — plant before the ground freezes.
Zone 11 has an average last spring frost of approximately none and a first fall frost around none. These dates vary by specific location — use your ZIP code in the plant app for precision based on the nearest NOAA weather station.
Good companion crops for onion include Carrots, Brassicas, Tomatoes, Beets. Avoid planting near Beans, Peas, Asparagus, which can compete for nutrients or attract pests.
Onion typically takes 90–120 days from transplant or direct sow to harvest in Zone 11. Expected harvest window: Jan – Mar.

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Onion in other zones
Crop Guides