Lily of the Valley (Convallaria majalis) is a charming perennial known for its delicate, bell-shaped white blossoms and intensely sweet fragrance. While traditionally a harbinger of spring, it can be successfully “forced” to bloom indoors, often during the winter months. Indoor forcing is an accelerated cultivation method that tricks the plant into breaking its natural dormancy cycle, requiring careful management of temperature and light to achieve an out-of-season display.
Sourcing and Preparing the Pips
Successful indoor cultivation of Lily of the Valley begins with specialized planting material known as “pips.” A pip is the dormant terminal bud or shoot of the plant’s underground rhizome, containing the potential for both leaves and the flower stalk.
The most reliable option for forcing is to purchase “prepared” or “precooled” pips from a supplier. These have already undergone vernalization, the necessary cold period required for flowering. If using pips divided from an outdoor patch, they must be subjected to this chilling treatment, which mimics winter and initiates the biochemical changes that trigger blooming.
Unprepared pips need a minimum of eight to ten weeks of temperatures consistently below 45°F (7°C) to complete vernalization. During this chilling period, store the pips in slightly moist peat moss or sand, enclosed in a plastic bag to retain humidity, and place them in a refrigerator. Keep them away from ripening fruits like apples and pears, which release ethylene gas that can inhibit flower development.
Detailed Planting and Environmental Setup
Once the pips are adequately chilled, they are ready for planting. Choose a shallow container, such as a bulb pan, that provides good drainage to prevent the rhizomes from rotting. Use a standard, rich, and well-draining potting mix, ideally peat-based or formulated for bulbs.
Before planting, soak the pips in lukewarm water for a few hours to rehydrate the roots. If the roots are very long, trim them slightly to fit the container, leaving at least four inches of healthy root attached. Plant the pips tightly together, spacing them about one to two centimeters apart, for a full display.
Plant the pips with the tips just barely exposed above the soil surface. Water the container thoroughly with warm water to settle the soil. For the initial stage of growth, place the container in a cool, dimly lit location, such as a basement or garage, where temperatures remain around 50–60°F (10–15°C). This environment encourages strong root development before top growth begins.
Ongoing Care and Forcing Management
After planting, initial care focuses on maintaining consistent moisture and monitoring for shoot emergence. The soil must be kept evenly moist but never saturated, which would cause the rhizomes to rot. Infrequent but steady watering is necessary during this early phase of root establishment.
Once green shoots emerge and reach two to four inches, the plant is ready for the transition phase to encourage blooming. Gradually move the container from the cool, dim location to a brighter spot with indirect light. The temperature must also be increased to the ideal range for flowering, typically between 65–70°F (18–21°C).
Maintaining high humidity is helpful during the forcing period to prevent leaf tips from browning. Achieve this by misting the foliage several times a day or placing the pot on a tray filled with pebbles and water, ensuring the pot base remains above the water level. Flowers should appear approximately three to four weeks after the pips are brought into the warmer, brighter environment.
Post-Bloom Care and Storage
Once the flowers have faded, the indoor forcing cycle is complete. Forcing is an exhaustive process, and the plant is highly unlikely to bloom again indoors the following season. Growers typically have two options for the forced pips.
The simplest option is to discard the spent pips, which is common practice for forced bulbs and rhizomes. Alternatively, the pips can be saved and planted outdoors to recover and bloom naturally in subsequent years. To save them, remove the spent flower stems and continue watering, allowing the foliage to remain and gather energy.
When the danger of frost has passed, the rhizomes can be transplanted into a shady or partially shaded area of the garden. They prefer rich, moist, and well-drained soil. Note that the pips will need a recovery period and may not flower again for one to two years after being forced indoors.