Most people think of onions as a spring crop, but fall is actually one of the best times to plant certain types of onions — especially if you want strong, early harvests next year. With the right approach, you can enjoy sweeter, bigger bulbs with less fuss and fewer pests.
This guide will walk you through everything you need to know to grow onions in the fall—from choosing the right type to planting, protecting, and harvesting.
🧠 Why Plant Onions in the Fall?
Planting onions in autumn gives them a head start:
- 🌱 Stronger root systems before winter dormancy
- ⏱️ Earlier harvests in late spring or early summer
- 🐛 Fewer pests like onion maggots and thrips
- 🌞 Uses winter/spring rains and avoids summer drought stress
✔️ Fall planting works best in mild climates (zones 6–10) or with cold-hardy varieties and good winter protection in colder zones.
🧅 Choose the Right Type of Onion
There are 3 types of onions based on day-length sensitivity. For fall planting, pick short-day or intermediate-day onions, since they form bulbs with less daylight.
| Type | Best For | Examples |
|---|---|---|
| Short-Day | Southern states (zones 7–10) | ‘Texas Sweet’, ‘Granex’, ‘Red Burgundy’ |
| Intermediate-Day | Zones 5–7 | ‘Candy’, ‘Super Star’, ‘Red Long of Tropea’ |
| Long-Day | Northern states (zones 6 and colder) | NOT ideal for fall planting |
🧄 Pro Tip: Fall is also the ideal time to plant garlic and shallots, which grow on a similar cycle.
📍 When to Plant Fall Onions
- Mild Climates (Zones 7–10): Plant from September to November
- Cool Climates (Zones 5–6): Plant in late August to early October, and be prepared to mulch heavily
You want onions to establish roots before the ground freezes, but not grow large tops (which can be damaged by cold).
🌾 How to Plant Fall Onions (Step-by-Step)
✔️ Step 1: Prepare the Soil
- Choose a sunny location with loose, well-draining soil
- Work in compost or aged manure
- Ideal pH: 6.0 to 6.8
✔️ Step 2: Select and Prep Sets or Starts
- Onion sets (small bulbs): Easiest for beginners
- Transplants: Also good; just ensure they’re cold-hardy
Avoid large sets (>¾”) — they’re more likely to bolt.
✔️ Step 3: Plant Properly
- Space onions 4–6 inches apart
- Rows 12–18 inches apart
- Plant sets 1 inch deep, pointed end up
❄️ How to Protect Onions Over Winter
Fall onions need help surviving cold snaps, especially in zones 5–6.
- Apply 2–4 inches of mulch (straw, shredded leaves) after planting
- In colder areas, use row covers or low tunnels
- Remove or reduce mulch in early spring to encourage growth
💧 Watering & Care
- Water regularly during dry fall weeks
- Onions prefer consistent moisture but hate soggy soil
- In spring, resume watering when growth restarts
- Fertilize with a nitrogen-rich amendment in early spring
🧅 When to Harvest Fall-Planted Onions
You’ll typically harvest in late spring to early summer, depending on your zone and variety.
Signs they’re ready:
- Tops fall over and begin to dry
- Neck of the onion becomes soft
- Bulbs push up from the soil
After harvest:
- Cure in a dry, well-ventilated area for 2–3 weeks
- Store in a cool, dark place (not in plastic bags)
🧠 Key Takeaways
- Fall planting = earlier, bigger, sweeter onions in spring
- Choose short- or intermediate-day varieties based on your region
- Mulch is critical for winter protection
- Proper spacing, watering, and patience are the key to a great crop
📕 This Article Was Brought to You By…
Know the Natives Plant Guide
If you’re planning your fall garden, you’ll love this book. It’s packed with seasonal growing tips and native plant profiles for a low-maintenance, resilient landscape.
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