Nicely and effectively grown in containers or in the mixed flower border, tuberose is also known as Mexican tuberose, nardo or azucena. Appropriate for growing outdoors in USDA Hardiness Zones 8 and warmer, plant the roots of tuberose after danger of frost is past elsewhere, growing it as a seasonal summer bulb like gladiolus or dahlia. Grow it as an accent in a mixed perennial border or in containers, harvesting the sweetly fragranced flowers to bring indoors and embellish bouquets.
Not known as a naturally occurring plant, the tuberose likely has origins in Mexico, and was domesticated by pre-Columbian natives. Dr. William C. Welsh of Texas A&M University states the tuberose was among the first plants brought back to Europe from the New World, and gardeners even along the American Gulf Coast enjoyed tuberoses in the 18th century.
There are 13 tuberose species, but typically the species Polianthes tuberosa is identified with the name. As a member of the century plant family, Agavaceae, a tuberose's foliage bears parallel-arranged veins and flowers with parts in multiples of three. All plant family members have origins in North and Central America.
Forming a cluster of thin, linear green leaves emanating from the ground, tuberose sends up a tall flower stem in summer to early autumn. The tip of the stem bears tubular, six-petaled, white flowers with a waxy texture that release an intensely sweet, alluring fragrance. Overall, the plant grows from anywhere between 2 and 4 feet in height but 18 to 30 inches in width.
Grown outdoors where winters lack prolonged subfreezing winter temperatures (USDA Hardiness Zones 8 and warmer), tuberose grows from a fleshy underground stem called a tuber. In garden catalogs or nurseries, they are grouped into the all-encompassing category of "summer bulbs," alluding to their need for warm soil and frost-free growing conditions.
In general, plant the tubers 2 inches deep in a sand-based soil in abundant sunshine, watering during the growing season when leaves and flowers are seen. A well-balanced liquid fertilizer is applied every two weeks in spring and summer. The foliage naturally yellows and dies back in autumn, when watering should be reduced and fertilizing stopped. Allow the soil to remain rather dry across the dormant winter period and in USDA Zones 7 and colder, the tubers should be dug up and stored in a cool, dry location in the house or basement so they do not freeze. In the warmest areas of USDA Zone 7, the tubers may successfully overwinter outdoors in the ground when protected by a thick layer of organic mulch.
More visually stunning than the regular species form is variety 'The Pearl,' with its extra row of white petals to make each blossom look fuller and more ornate. 'Mexican Single,' also a white-flowering selection, performs as a longer-lasting perennial in southern American garden regions such as Texas. Additional hybrid varieties now exist, the result of crossing Polianthes tuberosa with other Polianthes species, as well as plants in the genus Manfreda. These hybrids bear flower buds with blushes of peach or pink, but are primarily still white-flowering.