Lilies (Lilium genus) are popular flowering bulbs known for their dramatic height and varied bloom shapes. Successfully growing these flowers depends significantly on the correct placement of the bulb in the soil. Proper planting distance ensures the long-term health and impressive flowering of the plants.
Why Spacing Is Essential for Lily Health
The primary reason for providing adequate space between lily bulbs is to promote air circulation around the developing stems and foliage. Overcrowding creates a dense canopy that traps moisture, leading to a humid microclimate near the base of the plant.
This condition is favorable for the development of fungal diseases, which can rapidly diminish a plant’s vigor. The most common threat is Botrytis blight, also known as gray mold, which thrives in cool, damp, and poorly ventilated environments. This fungus attacks the leaves, causing tan or reddish-brown spots that eventually spread and kill the foliage. Reducing planting density is a core cultural control method recommended to suppress Botrytis by improving air flow.
Proper distance also mitigates competition for resources in the soil. When bulbs are planted too closely, the expanding root systems must vie for water and available nutrients, which can lead to stunted growth and smaller flowers. Allowing room for each plant to establish a healthy root zone ensures that every stem can reach its full potential.
Calculating Horizontal Spacing by Lily Type
The exact horizontal distance between bulbs is not uniform; it must be determined by the mature size of the specific lily hybrid you are planting. Spacing is always measured from the center of one bulb to the center of the next. For general planting in a garden bed, a minimum distance of 8 to 18 inches is recommended, depending on the variety’s expected height and spread.
Smaller, earlier blooming types, such as Asiatic lilies, are typically planted closer together, needing approximately 8 to 12 inches of space between bulbs. If you plan to leave the bulbs undisturbed for several seasons, allowing 12 inches is advisable to accommodate the natural multiplication of bulblets. These varieties do not demand as much room as taller types.
The larger and more fragrant Oriental and Orienpet hybrids require greater space to support their substantial growth. A good starting point for these mid-to-late summer bloomers is 10 to 12 inches between bulbs. Extremely tall varieties, particularly the large-bulbed Trumpet lilies or “lily trees,” need significantly more room, ideally at least 15 inches apart, to prevent crowding.
When planting in containers, spacing can be slightly reduced, but air circulation remains a factor. A guideline is to place three to five bulbs in a group, ensuring they are spaced far enough apart to allow for strong stem emergence and foliage development. This clumping method creates a visually appealing density while respecting the plant’s need for individual space.
Planting Depth and Soil Conditions
While horizontal spacing addresses above-ground health, planting depth is a separate, vertical consideration equally important for bulb development. A general rule for most lily types is to bury the bulb at a depth two to three times its own height. For an average bulb, this often translates to covering the top of the bulb with 4 to 8 inches of soil.
Deep planting is necessary because most lilies are “stem-rooting,” meaning they develop feeder roots along the underground portion of the stem, positioned above the bulb. The basal roots that grow from the bottom of the bulb primarily anchor the plant. Stem roots are the main mechanism for absorbing water and nutrients. Sufficient depth encourages the formation of these vital stem roots, stabilizes tall plants, and helps keep the bulb cool during warmer months.
Regardless of the distance between bulbs, the surrounding soil must be properly prepared. Lilies require well-draining soil, as standing water or heavy clay will cause the fleshy, scaleless bulb to rot quickly. It is beneficial to loosen the soil to a depth of 12 to 15 inches before planting and amend heavy soil with compost to improve drainage.