(Editor's Note: This article was originally published on August 15, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
The garden snowflakes, from the genus Leucojum and Acis (Amaryllidaceae), are perhaps not as popular as many of our other garden bulbs like lilies, tulips, crocus, etc, but they are deserving of space in the garden in regions where they can be successfully cultivated. At one time all the snowflakes were classified as Leucojum but more recently, most have been placed into a ‘new' genus called Acis. In reality, Acis is not really new at all; the plants in question were originally classified as Acis back in 1807 but in the 1880's were lumped into the genus Leucojum. With new DNA studies, the separation of many Leucojum back into Acis happened as recently as 2004. How do the two differ? Leucojum are generally larger plants with wider, strap-like leaves, hollow flower stems and white, bell-shaped flowers whose tepals (sepals and petals that look the same) are tipped in green. They look much like snowdrops on steroids! Acis on the other hand, are smaller, more delicate plants with narrow, grass-like foliage, solid flower stems and nodding bell-like flowers that are either pure white or tinted pink. Their flowers are more reminiscent of lily-of-the-valley. Of the 10 species that were once classified as Leucojum, there are now only two species still within that genus. The other eight are now reclassified as Acis.
The name Leucojum comes from the Greek ‘leukos' meaning white and ‘ion' meaning violet, in reference to the delicate fragrance emitted by the blooms of this genus. Morpholically and genetically, they are most closely related to the snowdrops (Galanthus). Among the snowflakes, they are the easiest to cultivate and hardiest, hence the most popular. There are two florally-similar species, the spring snowflake, L. vernum (zone 3) and the summer snowflake, L. aestivum (zone 4). In the wild, both inhabit damp to wet meadows and open woodlands, the former in Sardinia and the latter throughout east-central Europe. In the garden, both are planted in autumn much like your other typical fall-planted bulbs. The spring snowflake grows about 20 cm in height and blooms from late winter to mid-spring depending on where you live. The summer snowflake reaches to 60 cm and blooms late spring to early summer. Both are reasonably resistant to herbivores (as are most members of the Amaryllidaceae). In the garden, Leucojum prefer soil that does not dry out completely in summer (similar to snowdrop requirements). Sun to dappled shade is preferred. Both of these species are generally available in local nurseries or through mail-order bulb companies.
Above are details of the flowers and growing habit of Leucojum vernum. The introductory photo is a close-up of L. aestivum.
The genus Acis is probably in reference to the Greek mythological character called by that name, although some authorities say in Latin, ‘acis' means ‘pointed', a possible reference to the emerging foliage of this genus. Culturally, Acis are more challenging to grow. In the wild they inhabit dry grassy meadows. In the garden, they demand well-drained soil and a warm site. They need protection from excess winter wet and need to ‘bake' in the summer. Not particularly hardy, they are only suitable for zones 7 to 9. In North America, gardeners in California and Oregon have the best chance to grow Acis in the open garden. They are also worth trying in the SE States. Elsewhere they are best grown in pots kept in a bulb frame. The most accommodating of the Acis is the autumn snowflake, A. autumnalis. This exquisite beauty is native to Portugal, Spain, islands of the Mediterranean and Morocco. They flower from late summer through autumn and often bloom before they produce leaves. Thin, upright stems 10-15 cm are topped by a few nodding white bells. Typical of Acis, their leaves are winter-green and disappear by late spring. Very similar and slightly more robust is the species A. tricophylla, native to Portugal, Spain and Morocco. A pale pink-flowered counterpart is A. rosea from Corsica and Sardinia. There is also a spring-blooming Acis called A. nicaeensis. This species hails from southern France. This one sends up leaves in late fall that continue to grow into the spring then dry-off by mid-summer. These and the remaining Acis, are difficult to find. They are offered by some mail-order, specialty bulb companies or through seed exchanges. If grown from seed, they need 2-3 years to reach flowering-size.
Details of Acis autumnalis
No doubt the rarity, lack of hardiness and specific growing requirements of the Acis have contributed to the scarcity of this species as a garden ornamental. Leucojum on the other hand, are quite amenable to cultivation and can make a wonderful addition to the spring bulb display with their charming blooms and delicate fragrance.
I would like to thnak the following people for the use of their pictures: Galanthophile (L. aestivum close-up), kennedyh (L. vernum clump), tigerlily (L. aetivum close-up) and KMAC (A. autumnalis clump)