How deep should onion sets be planted?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.Planting onion sets correctly is the determining factor for a successful harvest. In the past, I planted onion sets that were 2 inches deep and harvested onions that were the size of marbles. I now adhere to the 0.75-1 inch (1.9-2.5 cm) rule of thumb, without fail. Sets that are planted too shallow tend to dry out, while sets planted too deep may limit the bulb's ability to expand. Always plant with the pointed side facing up, as this simple task can increase your chances of sprouting by 70%.
Depth Requirements
- 0.75-1 inch (1.9-2.5 cm) for bulb formation
- Measure from set base to soil surface
- Use finger-width as quick gauge (index finger ≈1 inch)
Spacing Strategy
- 4-6 inches (10-15 cm) between sets
- 12 inches (30 cm) row spacing for airflow
- Closer spacing = smaller bulbs, wider = risk of weeds
Orientation Impact
- Pointed end up triggers faster sprouting
- Sideways planting delays growth by 10-14 days
- Buried necks rot - keep top 1/4 exposed
The depth requirements for planting seeds are affected by the type of soil. For example, in my sandy plot in Michigan, I store my seeds at a depth of 1 inch (2.5 cm) to avoid drying. Gardeners with clay soil should use 0.75 inches (1.9 cm) as their depth point. The best method is to press out a set directly into prepared soil so that the neck of the set shows barely above the soil line.
Employ a dibble tool to maintain uniformity in planting depth by using a dibble with marked increments. I range mine with tape at 1 inch (2.5 cm). Multi-row planter's additional value from homemade depth gauges - nail a block onto a hoe at your desired depth. Spring planting windows can be quite tight, so speed is always a consideration.
Read the full article: When to Plant Onions: Expert Guide for Perfect Bulbs
