Polianthes is a tuberous genus of approx. 13 species from Mexico considered by some, especially recently using DNA analysis, to belong to the Agavaceae family, but has also been proposed to be included in the Asparagaceae family. Species have narrowly lance-like to strap shaped leaves and white, pink, or red flowers. The red flowered species are sometimes separated into the genus Bravoa. Dormant in winter, the species are summer growing and blooming. Some species need protection from freezing temperatures. The species most commonly grown, Polianthes tuberosa, is known for its fragrance. Hybrids between different species have started appearing recently, as have hybrids between Polianthes and Manfreda, another member of the Agavaceae family.
Polianthes ×bundrantii T.M.Howard is a hybrid between Polianthes howardii and Polianthes tuberosa. However, unlike Polianthes tuberosa, it doesn't have any scent that I can detect. Photos taken Aug. 2004 by Lee Poulsen. Note from wiki administrators: Kew refers to this name as unplaced, but we're not sure what that means.
Polianthes geminiflora syn. Bravoa geminiflora grows naturally in winter-dry oak forests in Mexico. It has flowers in pairs in early to mid summer that are reddish orange to yellow. This species may be a bit hardier than some of the others. Photos by Mary Sue Ittner show flowers in bud, then more fully open, and finally tubers on a 1 cm. grid.
Polianthes howardii is native to Jalisco and Colima in Mexico. It's a vigorous grower for me here in Honolulu, Hawai'i and blooms year-round. The flower colours are attractive in their unusual tones of coral, dusky pink, greyish-green and black. Inflorescences can grow up to 1 m tall. The foliage is evergreen. The fourth photo is by Nhu Nguyen. Photos 1,2,3,5 and 6 by Jacob Uluwehi Knecht.
Polianthes tuberosa is often sold as "the most fragrant bulb". It was popular in the Victorian era with the common name "tuberose". One synonym is Agave polianthes. It has a long history of cultivation around the world which makes its origin confused; it appeared in Europe around 1600 having been discovered in Central America. Some growing advice appeared on the PBS list here. Photographed by David Pilling. The second photograph shows the result of unwisely planting 10 bulbs in a 12" pot. In a cold Spring in North West England growth was slow to appear, and in future I would be inclined to keep the bulbs indoors until there were signs of life above ground.