How Deep to Plant Onion Sets and Seeds: Exact Depths That Work
By Kevin Parker · Updated October 2026 · 6 min read
Short answer: Plant onion sets about 1 inch deep with the pointed tip up, plant seeds 1/4 inch deep, and set transplants so the roots are covered and about 1 inch of white stem is buried below soil level. Getting depth right affects both how quickly onions emerge and how well-shaped the bulbs turn out.
Depth by Planting Method
| Method | Planting Depth |
|---|---|
| Seeds | 1/4 inch |
| Sets (small bulbs) | About 1 inch, tip up |
| Transplants (seedlings) | 1 inch of stem buried, roots covered |
Our sets vs. transplants vs. seeds guide compares these methods in more detail if you’re still deciding which to use.
How Deep to Plant Onion Sets and Seeds, Step by Step
A shallow furrow and a gentle hand beat guesswork. The same routine works for sets and transplants. Only the depth changes between the two methods. Depth is the first of the planting basics our how to grow onions guide builds on.
- Draw a furrow about one inch deep along the row.
- Set each onion set upright, pointed tip facing up.
- Space the sets four to six inches apart evenly.
- Cover them until just the tip may show.
- Firm the soil gently with your palm afterwards.
- Water the row well to settle everything in.
For seed, draw the drill only a quarter inch deep. Scatter the seed thinly along the drill line. Cover lightly and keep the surface evenly moist.
| Mistake | What you see | Fix |
|---|---|---|
| Planted too deep | Slow, patchy emergence; long, stretched bulb shapes | Match the depths in the table above; reset partly grown sets shallower |
| Planted too shallow | Roots drying out; plants rocking in the wind; sets pushing themselves out of the soil | Cover to the full depth, firm the soil, and water the row in |
Why Depth Matters
Planting too deep delays emergence and can force the bulb to form lower in the soil than ideal, sometimes resulting in elongated rather than round bulbs. Planting too shallow leaves roots exposed to drying out and the plant unstable in wind or rain, and sets planted too shallow can push themselves partly out of the soil as roots develop.
A Note on Sets: Which End Goes Down
Onion sets have a pointed end (where the shoot will emerge) and a flatter end with small root remnants. Always plant with the pointed tip facing up; planting upside down doesn’t necessarily kill the set, but it does delay and weaken emergence as the shoot has to redirect its growth.
Frequently Asked Questions
Does planting depth change for raised beds or containers?
No, the same depth guidelines apply whether you’re planting in the ground, a raised bed, or a container. What changes is spacing and drainage, not planting depth.
What happens if onion sets are planted too deep?
Sets planted significantly deeper than 1 inch typically emerge slower and may produce a more elongated bulb shape, since the growing bulb has to push upward through more soil as it expands.
How deep should onion sets be planted?
Plant each set about one inch deep overall. The pointed tip should sit facing straight up. Just the very tip may peek through afterwards.
How deep do you sow onion seed?
Sow onion seed a quarter inch deep only. Seed buried deeper sprouts slowly or fails entirely. Keep the shallow seedbed moist until seedlings appear.
Can onions be planted too deep?
Yes, and deep planting shows itself quite quickly. Emergence slows down and bulbs grow long shapes. Shallow planting causes the opposite set of problems.
Should the tip of an onion set stick out?
A tiny tip showing at the surface is fine. Birds sometimes tug at exposed tips in spring. Firm soil around each set to anchor it well.
Do transplants go deeper than onion sets?
Transplants sit with about one inch of stem buried. That buries the roots and white base fully. Only the green leaves stay above the soil.
Final Thoughts
Depth is one of the easiest things to get right once you know the target for your planting method. Pair correct depth with good spacing for the best shot at well-formed bulbs.
How This Guide Was Checked
The transplant depth here matches Ohio State University Extension’s fact sheet. Extension planting guidance for sets and seed was checked as well. Where gardening sites printed figures with no source, this guide left them out.
Written by Kevin Parker · grows onions in his own beds in California. Figures are checked against university extension and grower sources, linked on each page. More about Kevin.
