Tuberose, also known as polyanthus lily or by its Latin name, Polianthes tuberosa, grows natively in areas of Mexico and the extreme southern United States. A tender perennial, the plant features thick, tuberous roots, succulent leaves and large, erect flower spikes. Reaching up to 48 inches in height, tuberose produces numerous white, fragrant, tube-shaped blossoms in mid- to late summer. Although the plant performs best in USDA hardiness zones 8 through 11, gardeners in cooler zones may successfully grow tuberose with proper winter care.
Site and Soil
Tuberose requires a planting site that receives full sun and consists of fertile, well-drained soil. Amending the soil with 2 to 3 inches of organic compost or well-rotted manure prior to planting improves fertility to adequate levels. Tuberose will not thrive in water-logged soils. Planting bulbs outdoors in spring after all danger of frost has passed is recommended. Bulbs planted 2 to 3 inches below the soil surface and spaced 8 to 10 inches apart perform best.
Gardeners may also grow tuberose in containers, particularly in cooler zones. High-quality, well-drained potting soil in a container with drainage holes on the bottom creates the best growing medium for the plant. Plant bulbs 2 to 3 inches below the soil surface, with one bulb per each 8-inch container. Care requirements are the same for container-grown plants and tuberoses grown in the garden. Both need full sun, regular watering and fertilizing, and winter care depending on the hardiness zone.
Watering generously just after planting initiates new growth, which appears within a few weeks. Once green top growth appears, tuberose requires supplemental watering only on weeks that do not receive more than 1 inch of natural rainfall. Container-grown plants need weekly watering to thrive. Soil kept slightly moist during active growth, usually during the spring and summer months, yields the best results.
Twice-monthly applications of a balanced 8-8-8 NPK liquid fertilizer during the spring and summer months increases blooming and encourages new growth. Tuberose plants are heavy feeders and require supplemental fertilization to thrive and flower. If planted in well-amended soil, tuberose requires no fertilizer at the time of planting. Do not feed plants during the fall and winter when they enter a state of dormancy.
After blooming ceases, foliage allowed to remain on the plant provides nutrients for the bulbs and should be removed in late fall only when it begins to yellow. In zones 5 through 7, lifting the bulbs and storing until the next year prevents cold damage. Bulbs sustain injury if temperatures drop below 50 degrees Fahrenheit, so gardeners should remove them before this occurs. Dig up the bulbs, allow them to air-dry for several days, and then store in paper bags or boxes filled with peat moss at 70 to 75 degrees. In zone 8, tuberose bulbs may survive winter in the ground with heavy mulching. In zones 9 through 11, bulbs allowed to remain in the ground all year enter dormancy during winter and resume growth in spring.