Can You Grow Onions Indoors Year-Round?
By Ada Jones · Updated October 2026 · 7 min read
Short answer: you can grow green onions indoors year-round reliably, but full bulbing onions are a poor fit for indoor growing since they need more light intensity and space than most homes can realistically provide. If you want a steady indoor harvest, grow for the green tops, not the bulb.
Why Full Bulbing Onions Struggle Indoors
Onion bulbing is triggered by day length and needs strong light intensity, far more than a windowsill provides even with long exposure. Without a dedicated grow light setup delivering 14-16 hours of strong, full-spectrum light daily, indoor-grown bulbing onions typically produce thin, pale growth and little to no usable bulb. The space a bulb needs to size up properly is also hard to provide in most container setups indoors.
What Actually Works: Growing Green Onions Indoors
- Start from seed in a pot, from sets, or by regrowing store-bought scallion bases in water or soil
- Place in your brightest window (south-facing is best in the northern hemisphere) or under a basic LED grow light for 12-14 hours a day
- Keep soil consistently moist, or change water every 1-2 days if growing in water
- Harvest by snipping the green tops as needed — most varieties regrow several times from the same base
| Light Source | Good for Full Bulbs? | Good for Green Tops? |
|---|---|---|
| Sunny south-facing windowsill | No, too low intensity | Yes |
| Basic LED grow light, 12-14 hrs/day | Rarely, unless high-output | Yes, reliably |
| High-output full-spectrum grow light on a timer | Possible with enough intensity | Yes, reliably |
This approach gives you a genuinely reliable, year-round harvest of usable green onion tops, which is a realistic win compared to chasing a full bulb indoors.
FAQ
Can grow lights make full-size indoor onion bulbs possible?
With a strong enough full-spectrum grow light and large enough containers, small bulbs are possible, but most home setups won’t match outdoor results, and the electricity cost rarely pencils out compared to just buying onions.
How many times can I regrow the same green onion base?
Typically 2-4 regrowths before the base weakens and yields get smaller and slower — at that point it’s worth starting a fresh base or a new pot from seed or sets.
Final Thoughts
Grow bulbing onions outdoors and green onions indoors — trying to force a full bulb inside usually disappoints. See our water-regrowing guide to get started today with what you already have in the fridge.
How This Guide Was Checked
Based on indoor-growing light requirements research and grower-reported results from indoor onion-growing attempts. Questions about your setup? Contact us.
Related Onion-Growing Guides
- How to Grow Onions in Pots and Containers
- Best Soil and pH for Growing Onions
- How to Grow Green Onions (Scallions and Spring Onions)
- How to Grow Big Onions: Maximizing Bulb Size
See the full How to Grow Onions guide for the complete seed-to-harvest walkthrough.
