When Are Red Onions Ready to Harvest? Signs, Timing, and Expert Tips for Gardeners
Introduction
Growing your own red onions is a rewarding experience — their stunning colour, sweet yet punchy flavour, and long storage life make them a favourite for home gardeners. But knowing exactly when red onions are ready to harvest is key to getting the biggest, best-tasting bulbs.
Harvest too early, and you’ll miss out on their full size and sweetness. Wait too long, and they risk splitting, rotting, or losing shelf life.
In this guide, you’ll learn how to tell when red onions are ready to pick, how to harvest them without damage, and how to cure and store them for long-lasting use.
How Long Do Red Onions Take to Grow?
Red onions are typically ready to harvest 100 to 120 days after planting from sets or seedlings. This can vary slightly based on:
- Weather conditions
- Soil type and fertility
- Onion variety
You can start harvesting young or “green” onions earlier, but for full-size storage bulbs, you’ll need to wait until late summer.
Best Time of Year to Harvest Red Onions
In the UK and most temperate regions:
| Planting Time | Harvest Window |
|---|---|
| Early spring (March–April) | Late July to early September |
| Autumn planting (mild regions) | June–July the following year |
The key indicator isn’t just the calendar — it’s the plant’s physical signs.
Signs Your Red Onions Are Ready to Harvest
Here are the top signs to watch for:
✅ 1. Fallen or Yellowing Tops
Once the green leaves (tops) begin to flop over and turn yellow or brown, it’s a clear sign the bulb has stopped growing.
🔎 Look for 50–80% of the tops to have fallen naturally.
✅ 2. Bulb Size is Fully Developed
Gently scrape back the soil from one or two onions and check their size:
- Should be rounded and firm, at least 3–4 inches wide for mature bulbs
- Outer skin should start to feel papery or dry
✅ 3. Neck Feels Soft and Thin
The “neck” (where the stem meets the bulb) should be:
- Thin, soft, and dry
- No longer fleshy or moist
This means the onion has stopped sending nutrients to the bulb and is ready to be lifted.
How to Harvest Red Onions Step-by-Step
1. Choose a Dry Day
Pick a day with no rain forecast — this helps prevent rot during curing.
2. Loosen Soil Gently
Use a hand fork or trowel to loosen the soil around each bulb — avoid stabbing the onion directly.
3. Lift Carefully
Grasp the base of the leaves and gently pull the onion from the soil. Shake off excess soil — do not wash.
4. Inspect the Bulbs
Look for:
- Firm bulbs with dry skins
- No splits or signs of rot
Use any damaged bulbs quickly — they won’t store well.
Curing Red Onions for Storage
To store red onions long-term, you’ll need to cure them for 2–3 weeks.
| Step | Details |
|---|---|
| Lay them out | In a dry, well-ventilated area — not in direct sun |
| Avoid stacking | Leave space between each bulb |
| Turn regularly | Every few days to dry evenly |
| Wait until | Skins are papery and necks are fully dry |
💡 Tip: You can cure onions on a wire rack, in a greenhouse with airflow, or under a covered porch.
How to Store Red Onions After Harvest
| Method | Shelf Life | Tips |
|---|---|---|
| Braiding or bunching | 3–6 months | Store in cool, dark, dry place |
| Mesh bags or crates | 3–8 months | Ensure good airflow |
| Fridge (short term) | 2–3 weeks | For sliced or soft onions |
| Freezer (chopped) | 6–8 months (blanched or raw) | Best for cooking use |
Avoid storing onions near potatoes — the moisture and gases reduce shelf life.
Can You Harvest Red Onions Early?
Yes! You can:
👉 Harvest as Spring Onions
- When the bulbs are still small
- Leaves are green and upright
- Use fresh in salads or cooking
👉 Harvest as Green Onions
- 60–80 days after planting
- Before bulbs swell fully
- Ideal for quick meals — not for storage
Early harvest = milder flavour, shorter shelf life.
Common Mistakes to Avoid
🚫 Harvesting too soon — Small, immature bulbs won’t cure or store well
🚫 Leaving in wet soil — Leads to rot and fungal problems
🚫 Washing before curing — Encourages mould during drying
🚫 Cutting the tops too early — Wait until fully dry
🚫 Storing with bad airflow — Causes sprouting or softening
Patience pays off with onions — a few extra weeks can make all the difference.
Companion Harvest: What to Grow and Harvest with Red Onions
| Companion Veg | Why It Works |
|---|---|
| Garlic | Same harvesting window |
| Carrots | Similar soil prep and watering |
| Lettuce | Can be grown and harvested earlier |
| Beetroot | Similar bulb shape, different depth |
| Leeks | Follow-on crop after onion harvest |
Plan your allotment layout to maximise soil space and crop rotation efficiency.
What To Do After Harvest
✔️ Clean off dry soil gently
✔️ Cure for 2–3 weeks in a dry, ventilated place
✔️ Trim the roots and tops once fully cured
✔️ Label your harvest if growing multiple varieties
✔️ Store properly for long-term use
✔️ Save the best bulbs for planting next season (if using open-pollinated types)
Conclusion
Red onions are one of the most rewarding crops for home gardeners — but knowing when to harvest them is crucial for flavour, size, and storage.
Look for fallen tops, firm bulb size, and dry necks as your harvest cues. Take the time to cure them properly, and you’ll enjoy your homegrown red onions for months to come in everything from roasts to salads to stews.
With the right timing and a little care, your red onion crop will be one of the tastiest and longest-lasting harvests in your garden.
Top 10 FAQs About Harvesting Red Onions
1. How do I know when red onions are ready to harvest?
When 50–80% of the tops have flopped over, and the necks are soft and dry.
2. Can I harvest red onions early?
Yes — as spring or green onions, but they won’t store long.
3. What happens if I harvest too early?
Bulbs may be underdeveloped, lack flavour, and won’t store well.
4. Should I wash onions after pulling them?
No — brushing off dry soil is fine. Do not wash before curing.
5. How long do onions take to cure?
Usually 2–3 weeks in a dry, well-ventilated spot.
6. Can I dry onions in the sun?
A few hours is okay, but avoid prolonged direct sunlight — it can cause sunscald.
7. Can I eat onions right after harvest?
Yes — they’re perfectly safe fresh, though the flavour improves after curing.
8. How do I store red onions after curing?
In a cool, dark, well-ventilated area like a shed or pantry.
9. Why are my onions splitting or sprouting?
Usually due to overwatering, late harvest, or poor curing.
10. Do red onions store as well as yellow onions?
They can — with proper curing and storage, they last 3–6 months or longer.