From our perspective, we, the tuberose bulbs (Polianthes tuberosa), are not naturally inclined to bloom during your winter. We are native to warm climates and our life cycle is dictated by long, sunny days and warm nights. Our bulbs enter a necessary dormancy after our summer blooming period to conserve energy. To force us to bloom indoors in winter is to fundamentally trick our internal biological clock into believing it is summer. This process requires carefully replicating the specific environmental conditions we need to break dormancy and initiate flower spike development.
Before you even think of warmth and light, we require a period of cold, moist rest. This simulated "winter" is crucial for us to reset our hormonal balance. Without it, we will not have the energy or the chemical signals to flower later. Please place our bulbs in a paper bag or a box with slightly moist peat moss or vermiculite. Store us in a dark location at approximately 50-55°F (10-13°C) for 4 to 8 weeks. This chilling period satisfies our dormancy requirement and prepares our apical meristem—the growing point inside the bulb—to shift from vegetative rest to reproductive growth once favorable conditions return.
After our chilling period, we are ready to be awakened. Gently pot us in a well-draining, lightweight potting mix, ensuring the narrow tip of the bulb (our nose) is just level with or slightly above the soil surface. Do not bury us deeply. The most critical factor at this stage is bottom heat. Our root system and growing point respond vigorously to warm soil. Place our pot on a seedling heat mat set to 70-75°F (21-24°C). This warm soil is a powerful signal that mimics the warm earth of our native summer habitat, stimulating rapid root development which is the foundation for a strong flower spike.
As our green shoot emerges from the bulb, we immediately begin photosynthesis to fuel our growth. Your winter sun is weak and the days are short—conditions we find entirely inadequate. To produce the sugars needed to develop our famously fragrant flower spike, we require intense, direct light for a minimum of 6-8 hours daily. Place us in your brightest south-facing window. However, for a guaranteed bloom, you must supplement with a full-spectrum grow light positioned 6-12 inches above our emerging foliage for 12-14 hours a day. This extended "daylength" is a key trigger to initiate flowering.
Our growth will be rapid under these ideal conditions, and we will have high demands for water and nutrients. Keep our soil consistently moist but never soggy; waterlogged conditions will cause our bulbs to rot. Once our green foliage is 4-6 inches tall, begin feeding us with a balanced, water-soluble fertilizer diluted to half-strength every two weeks. This provides the essential phosphorus to support the development of our flower spike and the potassium to strengthen our overall structure. As we begin to form the bud spike, you may increase the light and slightly increase the fertilizer strength to support this final, energy-intensive push.
