Amaryllidaceae. Horticultural cultivar of the triandrus group, obtained at the beginning of the 20th century and awarded by the Royal Horticultural Society. It results from crossings involving Narcissus triandrus, a wild species of the Iberian lawns and garrigues and the northwest of the peninsula.
The plant reaches 30 to 40 cm in height. The leaves are upright, narrowly ribbon-like, dark green. Each stem bears two to three flowers, sometimes more, this multiflore characteristic being inherited from the parent species. The flowers are creamy white with a slight pale yellow tint at opening, evolving to a purer white with age. The tepals are distinctly reflexed backward, giving each flower a very distinctive slender and winged appearance. The crown, in an open funnel shape and slightly lobed at the edge, is white to cream. The entire clump in full bloom produces a particularly light and graceful effect, clearly visible when the stems sway in the wind.
In its natural habitat, the type species blooms from March to April. In cultivation, 'Thalia' blooms in April-May, among the late mid-season daffodils.
It is cultivated in any well-drained soil, ordinary to slightly fresh, in full sun or partial shade. Robust and perennial, it naturalizes readily in late-mown lawns and performs well in pots.