Depth and spacing
See how deep and how far apart, drawn to scale in a slice of soil.
Ranges are typical guidance and vary with variety and soil; the label on your bulbs wins. Depth is measured from the soil surface to the base of the bulb, corm, tuber or rhizome. The two-to-three-times-its-height rule is general RHS-style advice for bulbs and corms; it does not apply to surface-planted rhizomes such as bearded iris. RHS: bulbs.