Leucojum is a small genus of bulbous flowering plants in the family Amaryllidaceae (order Asparagales), native to Eurasia and widely known as snowflakes. As currently circumscribed — following a major taxonomic revision in 2004 — the genus contains just two species: Leucojum aestivum (summer snowflake or Loddon lily) and Leucojum vernum (spring snowflake). Most of the species formerly included in Leucojum have been transferred to the related genus Acis, after molecular and morphological studies showed that the broadly defined Leucojum was paraphyletic.
Both species grow from bulbs and produce pendant, bell-shaped white flowers, distinguishable from the related snowdrops (Galanthus) by having green or yellow markings at the tips of all six tepals rather than only the inner three. Leucojum also has hollow flower stalks (scapes) and broad, strap-shaped leaves — 5–20 mm wide in L. aestivum and up to 25 mm in L. vernum — contrasting with the narrower, thread-like leaves of Acis. Seeds are relatively large, 5–7 mm across.
Leucojum aestivum is native to Europe, the Middle East, and the Caucasus, and has become widely naturalized in Japan, Australia, North America, and Uruguay. Leucojum vernum is found naturally across southern and central Europe from Spain to Ukraine. Both species favour damp environments: wet meadows, stream banks, ditches, and shady woodland habitats.
The genus was erected by Carl Linnaeus in 1753. Together with Acis and Galanthus, Leucojum belongs to the tribe Galantheae within the subfamily Amaryllidoideae.
Etymology
The name Leucojum derives from Greek λευκός (leukos, “white”) and ιόν (ion, “violet”), describing the white, sweetly scented flowers. The alternate spelling Leucoium is also used. Common names include snowflakes, St. Agnes’ flower (referencing the patron saint of virgins and gardeners), and snowbells.
Distribution
Leucojum is native to Europe (excluding the north-west) eastward through Turkey to Iran. L. aestivum has been widely naturalized throughout much of the world, including Japan, parts of Australia, North America, and Uruguay. Both species favour damp habitats — wet meadows, ditches, and shady woodland.
Taxonomy Notes
The genus was established by Carl Linnaeus in 1753 with L. vernum and L. autumnale, with L. aestivum added in 1759. The genus Acis was first proposed by Richard Anthony Salisbury in 1807 but not widely accepted until 2004, when molecular and morphological analysis confirmed that the broadly defined Leucojum was paraphyletic. Nine species with narrow leaves, solid stems, and unmarked flowers were transferred to Acis, leaving Leucojum with only its two current species.
Cultivation
Both Leucojum species are considered tough garden plants for damp soils. They perform well in western European gardens where the soil does not dry out completely in summer. L. aestivum thrives particularly on clay soils; L. vernum does well in moist, sunny or semi-shady positions and flowers around the same time as snowdrops. Bulbs should be replanted promptly after lifting, as desiccation causes failure to establish. Pests include the narcissus bulb fly (Merodon equestris); slugs and snails may eat flowers; and the fungus Peyronellaea curtisii can cause leaf damage.
Propagation
Leucojum can be propagated by division of established clumps or from seed. Seeds require a cold period to break dormancy and take 4–5 years to reach flowering size.
