Lilies (genus Lilium) are highly prized ornamental plants, celebrated for their dramatic blooms and captivating fragrance. Propagation offers a practical solution for gardeners looking to expand their collection without purchasing new bulbs. This method creates new, genetically identical plants from existing stock, ensuring they possess the same desirable characteristics as the parent. Lilies are cooperative, offering several distinct and effective vegetative methods to increase their population.
When to Propagate and Essential Preparation
The optimal time to propagate lilies is during their natural dormant period, generally from late summer through early fall, after the foliage has died back. This timing allows newly formed propagules time to establish a root system before winter dormancy. Working with dormant bulbs minimizes shock and stress, leading to higher success rates. Since lily bulbs lack a protective outer tunic, handle them carefully and replant quickly to prevent drying out.
Before beginning, gather specific tools for a sanitary operation. Use a sharp, sterilized knife or clippers for clean cuts, which minimizes the wound area and reduces infection risk. Sanitizing tools with a 10% bleach or alcohol solution prevents the spread of pathogens. A supply of fungicide or cinnamon powder is beneficial for dusting cut surfaces, providing a protective barrier against decay.
Increasing Stock Through Bulb Division
Bulb division is the most straightforward method, suitable for established lily clumps that have grown dense over several seasons. Lilies naturally reproduce by forming small bulblets, known as offsets, around the base of the main bulb. Overcrowding, often indicated by shorter stems and fewer flowers, signals that the clump is ready for division, typically needed every three to five years.
Carefully dig up the entire clump using a garden fork placed 6 to 8 inches away from the stems to avoid damaging the bulbs. Gently remove the excess soil to expose the individual bulbs and their connections. Naturally formed offsets usually separate from the parent bulb with a gentle twist or pull. If necessary, use a sterilized knife to divide firmly attached clusters, ensuring each resulting bulb has its own section of the basal plate and some roots.
Replant these separated bulbs immediately at a depth one and a half to three times their height, with the pointy end facing up. Larger, flowering-size divisions can be expected to bloom the following season. Discard any bulbs that show signs of rot or disease to maintain the health of the remaining stock.
High-Yield Propagation Using Scaling
Scaling utilizes the individual, fleshy layers of the lily bulb to produce a high number of new bulblets from a single parent plant. This method is effective because each scale stores enough energy and genetic material to regenerate a complete new plant. Begin by selecting a healthy, firm mother bulb and gently removing six to ten of the outermost scales.
Ensure a small piece of the basal plate remains attached to the base of each scale. If the scale breaks off above this plate, it cannot form a new bulblet. Clean the harvested scales and dust them with a fungicide or rooting hormone mix to protect the cut surface from infection.
Place the scales in a sealed plastic bag with a slightly moist incubation medium, such as peat moss or vermiculite. Store the bag in a warm, dark environment, ideally around 70°F, for two to three months. During this time, small bulblets, often multiple per scale, will form where the scale detached from the basal plate.
After bulblet formation, the scales require cold stratification, which mimics winter dormancy and encourages future top growth. Move the bag to a refrigerator for a chilling period of six to twelve weeks. Once complete, gently separate the tiny bulblets from the mother scale and plant them in a nursery bed or small pot to grow on.
Harvesting and Planting Natural Offsets
Lilies offer two other forms of naturally produced, ready-to-plant offsets: stem bulblets and aerial bulbils. Stem bulblets are small, fully formed bulbs that develop along the underground portion of the stem, often clustered near the soil surface. Harvest these when the main bulb is lifted for division in the fall, then detach and plant them separately.
Aerial bulbils are small, dark, bead-like structures that form above ground in the leaf axils of certain varieties, such as the Tiger Lily (Lilium lancifolium). These bulbils ripen in late summer or early fall and can be brushed off the stem when they are plump and mature. Both stem bulblets and aerial bulbils are miniature bulbs that can be planted directly into a prepared nursery bed.
Plant these natural offsets very shallowly, often with just an inch or two of soil covering them. While they are a convenient source of new plants, they take longer to reach flowering maturity compared to a large, divided bulb, typically requiring one to three years of growth before producing their first bloom.
Establishing New Lily Plants
Successful establishment relies on providing optimal growing conditions immediately after planting. Lilies thrive in well-draining soil rich in organic matter, maintaining a slightly acidic to neutral pH (6.0 to 7.0). Prepare the planting site by loosening the soil to a depth of 12 to 15 inches and incorporating compost or grit to ensure free root growth and prevent waterlogging.
Small propagules, such as bulblets from scaling or aerial bulbils, should be planted in a dedicated nursery area or containers for monitoring and protection. Planting depth is relative to size: small bulblets are planted shallowly, just covering the tip, while larger divisions are planted deeper (about 6 inches). Deeper planting provides stability for tall stems and helps keep the bulb cool.
Initial watering should be thorough to settle the soil around the new roots, and consistent moisture is necessary during the active growing phase. For the smallest propagules, protection during the first winter is recommended; a layer of mulch helps insulate the shallowly planted bulblets from extreme cold.