How to Care for Tuberose Bulbs

Although they're called bulbs, the structures that give rise to tuberose (Polianthes tuberosa) plants are enlarged roots more properly called rhizomes or tubers. The tuber sends out clumps of long, narrow leaves that resemble grass. The flower stalks grow 1 to 3 feet tall and bear intensely fragrant, white, single to double, waxy flowers.

Grow tuberose in containers anywhere. Give each tuber a 6-inch-wide pot with drainage holes or plant two or three tubers in a wider pot with holes, giving each tuber about 5 to 6 inches of growing space. They'll grow outdoors in U.S. Department of Agriculture plant hardiness zones 7 through 10. Plant the tubers with their tips about 2 inches below the soil surface and space them about 6 inches apart. Plant containers in early spring indoors and for gardens, time planting for after the last frost date for your area. The soil should be deep, loose, well-draining and rich in organic matter.

Plant tuberose in full sun except in areas with hot summers, where partial or full shade is suitable. The plants bloom in summer and possibly into fall, and need regular watering to grow well. Water tuberose deeply every five to seven days while they are growing and blooming. After the plants have finished blooming, the foliage will turn yellow. Stop watering and let the foliage die back.

If your tuberose are in alkaline soil or you have alkaline water, fertilize with an acid fertilizer after growth begins. Use a product like water-soluble azalea food with an N-P-K ratio of 30-10-10 applied at the rate of 1 tablespoon mixed with 1 gallon of water given every two weeks. For neutral to slightly acidic soils or water, use an all-purpose, water-soluble fertilizer such as 24-8-16 mixed at the same rates and time intervals as for the acid fertilizer. Stop fertilizing tuberose after blooming.

Except for cutting flowers for floral arrangements, tuberose doesn't need pruning. After the foliage has dried out in fall, in areas outside of tuberose's hardiness range, dig up the tubers and cut off the dried foliage with pruning shears sterilized by dipping them in rubbing alcohol to prevent spread of diseases. Allow the tubers to dry out in a cool, shady, well-ventilated area for two weeks before storing. Store them in a frost-free area over the winter, layering them with vermiculite or peat. Before replanting the tubers in the spring, you can remove the offsets from around the original tuber and plant those separately. Plant them more closely and more shallowly than the large tuber, but otherwise the care is similar. They will reach blooming size in about two years. Tuberose generally have no problems with pests or diseases.