The genus Lilium, commonly known as true lilies, offers spectacular and fragrant flowers for the garden, grown from fleshy, scaly bulbs. Unlike common garden bulbs that have a protective tunic, lily bulbs are delicate and require careful handling to prevent drying out before planting. Successful growth depends on proper initial planting technique, which ensures the bulb is anchored correctly and protected from environmental stress. Getting the planting depth right is the single most important factor for the lily’s establishment, stability, and future robust flowering.
Timing and Location Preparation
The ideal time to place lily bulbs in the ground is in the fall, approximately four weeks before the first expected hard frost. This timing allows the bulb to establish a healthy root system before the ground freezes solid, supporting strong growth the following spring. Spring planting is also acceptable, especially in regions with harsh winters, but it should be done as soon as the soil becomes workable.
Lilies generally perform best in full sun, meaning six or more hours of direct sunlight daily, though they can tolerate partial shade in hotter climates. A well-draining location is necessary because lily bulbs are highly susceptible to rot if left sitting in saturated soil. Heavy clay soil should be amended with organic matter, such as compost or well-rotted manure, to improve porosity and drainage. Lilies thrive in a soil environment that is slightly acidic to neutral (pH 6.0 to 7.0).
Determining the Ideal Planting Depth
The depth required depends on the lily’s unique root structure and type. Lily bulbs produce two distinct sets of roots: basal roots, which grow from the bottom, and stem roots, which develop along the stem section below the soil surface. Deep planting encourages the growth of these stem roots, which absorb most of the plant’s nutrients and water, and provide structural stability for the tall stem.
The general guideline for most popular lily hybrids (e.g., Asiatics and Orientals) is to plant the bulb two to three times its height. For a two-inch bulb, this means setting the base roughly six inches below the soil surface, or up to eight inches deep for larger bulbs. Planting deeper helps keep the bulb cooler during hot summer months and provides better anchorage for the stem. Bulbs planted in light, sandy soil should be placed deeper to retain moisture, while those in heavy, clay-rich soil can be planted slightly shallower.
A crucial distinction exists between stem-rooting lilies, which benefit from deep planting, and basal-rooting lilies. Basal-rooting types, such as the Madonna lily (Lilium candidum), only produce roots from the base and should be planted much shallower, often with only an inch or two of soil covering the top. Understanding the lily type is essential for determining the correct depth. Deep planting significantly increases the stem root system for hybrid varieties, leading to better flower quality and plant height.
Step-by-Step Planting Process
The planting process begins by digging a hole that is sufficiently wide and deep. The hole must accommodate the required planting depth plus extra space for preparing the base, and be wide enough for the basal roots to spread naturally. Loosening the soil at the bottom of the hole encourages initial root growth and improves the growing environment.
A small mound of coarse sand or grit should be placed at the base of the hole, directly beneath where the bulb will sit. This enhances localized drainage, preventing water from collecting around the sensitive bulb scales and reducing the risk of rot. The lily bulb is then positioned gently onto this mound with the roots facing downward and the pointed growing tip facing straight up.
The hole is then carefully backfilled with the amended soil, ensuring the soil is worked around the bulb without leaving large air pockets. The soil should be firmed gently over the bulb, but not overly compressed, which could impede the stem’s emergence. Immediately after backfilling, the area should be watered thoroughly to settle the soil and eliminate any remaining air pockets.
Essential Post-Planting Care
Following the initial watering, maintaining consistent soil moisture is important as the bulb establishes its root system. Lilies require about one inch of water per week during the growing season if natural rainfall is inadequate, but the soil should never be waterlogged. Deep, infrequent watering is preferable to light, frequent sprinkling, as it encourages the development of deeper, more resilient roots.
Applying a two to four-inch layer of organic mulch, such as straw or shredded leaves, around the planting area is beneficial. This layer helps regulate soil temperature, keeping the lily bulbs cool in the summer and insulating them from extreme temperature fluctuations in the winter. Mulch also suppresses weeds and retains soil moisture, reducing the need for constant watering.
Fertilization is not usually necessary at planting time. When shoots emerge in the spring, however, a balanced fertilizer can be applied to support vigorous growth. A complete formulation, such as a 10-10-10, can be lightly scratched into the soil around the plants. To deter common pests like voles or slugs, protective measures such as wire cages or slug baits can be helpful.