The rain lily, genus Zephyranthes, AKA zephyr lily

The genus Zephyranthes (commonly called rain lily, zephyr lily, and fairy lily) is a group of New World bulbs more closely related to Amaryllis than the true lilies, genus Lilium. In nature these plants are native to warm temperate, subtropical, and tropical regions ranging from the southeastern USA through Central America and into South America. Due to their great beauty and vigor, several have become established throughout the warmer climates of the world including parts of Africa, Asia, Australia and even many south Pacific Islands.

In this article we’ll be looking at three commonly grown rain lilies: Zephyranthes candida, carinata, and citrina. What makes these a perfect trio is their relative cold hardiness, ease of cultivation, and variation in color – white, pink and yellow, respectively. What’s more, they are so popular that all three are easily obtained from normal garden centers, big box stores, as well as specialty nurseries.

Rain lily bulbs are tunicate type bulbs, similar to Narcissus, Amaryllis, and Lycoris, usually not more than 2-3 centimeters in diameter. They readily form new bulbs by offsets, which are of course genetically identical. Many also easily germinate from seed, thus they can form large, clumping colonies, sometimes carpeting the ground. Their leaves are grass-like and quite short, usually not more than 30 cm long. They are typically evergreen, but during cold snaps they can go fully dormant.

Flowers are borne singly, held in an upright position, are relatively large and showy, and have a variety of colors ranging from white to pink and yellow. Petals are uniform, broad, prominently veined, concolor, and six in number. The center of the flower is dominated by six large, elongate anthers, typically yellow to orange in color. Flowers are held just above the leaves on relatively short, fleshy scapes. Flowering ranges from spring through early autumn. Many flower most abundantly after significant rains, hence their common name, rain lily.

The following are descriptions of the three above mentioned species, focusing on their distributions (both native and naturalized ranges), habit, and specific information about each.

Z. candida – a species originally from southern South America – Argentina, Uruguay, Paraguay, and southern Brazil, having become naturalized over much of the world from the southeastern USA, the West Indies, southern Africa, southern Asia including China, Korea, Japan, as well as Australia (Queensland), and a number of south Pacific Islands. It is perhaps one of the easiest in the genus to keep happy, withstanding both fairly heavy frosts to scorching hot summers.

The flowers are pure white (sometimes blushed with pink) with a green center, bright yellow-orange stamens, and are up to 5 centimeters across. The petals are relatively narrow and pointed, giving the flower a star-like quality. The flowers commonly open en mass after heavy rains, giving quite a show. The leaves are rather thick and curled inward, giving the overall impression of a sedge or rush – another interesting feature of this species, and possibly the reason why it is relatively cold hardy.

This plant seems to flower most abundantly in late August and September. In my observations of it in Japan, it grows best in full sun, forming large, dense clumps that expand through time, but are not particularly invasive. It is said to be the most cold hardy of the more commonly grown species, but prefers hot conditions in summer. That said, it has been successfully grown in cool summer areas such as coastal California and Oregon, and even the warmer parts of the UK and Ireland.

Though sometimes called the Peruvian swamp lily, it apparently is not actually native to that county, but was originally found further south in moist grasslands and marshy areas along rivers. Other common names include white zephyr lily, white rain lily, and autumn zephyr lily.

Z. carinata – originally native to Mexico and Guatemala, it is now found from the southern USA to Columbia and sporadically thru other parts of South America. It is also established in eastern Australia, southern China (likely India and Indochina as well), and into southern Japan, South Korea and several south Pacific Islands. It is said to be a rapid colonizer in South American sugarcane fields and pasture lands.

This is the famous large flowered, hot pink rain lily, boasting flowers up to 10 centimeters in diameter – a true giant among otherwise dainty size flowers. The flowers are deep pink with darker rosy-red flushing, a white and green center, and deep yellow-orange stamens. The petals are very broad and overlapping, giving the flower a more massive look. Like others of the genus, they flower most abundantly following heavy rain. The leaves are grassy and strap-like, glossy, and purplish near their attachment to the bulb.

This plant tends to flower starting mid summer, during the hottest weather. In Japan I’ve seen it growing in semi-shade near tree lines as well as in full sun. One colony in particular was memorable, growing on a grassy roadside that had been recently burned. Their leaves had all been completely destroyed, yet the large colony was in full, resplendent flower – a testament to this species’ hardiness. This is another zephyr lily that is said to be rather cold resistant, grown up to 2000 meters elevation in parts of South America, though it is probably less hardy than Z. candida.

This species has also been designated Z. grandiflora (an illegitimate name), though several sources continue to place it under this name. This species is also sometimes confused with the smaller flowering Z. rosea. Zephyranthes carinata goes by the common names pink rain lily and pink zephyr lily.

Z. citrina – this plant’s origin is obscure with most reliable sources stating it native to the Yucatan Peninsula, Mexico. Currently, it is found in warm temperate to tropical areas around the world from the southeastern US gulf states, the West Indies (widespread), Central and South America, Hawaii, southern Asia, Japan, the Cook Islands, and parts of Africa.

The most notable feature of this plant is its brilliant yellow flowers. Though quite lovely, they are relatively small, normally not more than 5 centimeters across. They are brilliant yellow, generally cupped, with yellow stamens. The petals are fairly broad and stout, and slightly overlapping. The grass-like leaves are a dull green.

This species tends to flower from late summer into early fall. In my area of Japan it is not a common garden flower, and frankly it has not been a good performer for me in the garden. In the the southeastern US gulf states, from Florida to Texas, it has become naturalized, forming impressive colonies. These are said to be the result of copious seed production rather than by offsets. Interestingly, this species commonly forms seed through the development of embryos without fertilization taking place (apomixis).

Z. citrina is sometimes sold under the name Z. sulphurea. It goes by the common names yellow rain lily and citron zephyr lily. A number of yellow colored “rain lilies” exist, though most are quite rare in cultivation. To see some unusual yellow rain lilies (Zephyranthes species and others) check out Jim Shield’s Garden Notes. Many of these you’ll only see in specialty gardens.

As for cultivation in the open garden, rain lilies are pretty easy provided the climate is adequate. These are plants from humid climates, but as long as the roots remain moist, they can take a lot of heat – after all, they thrive in the gulf coast states of the USA where daily highs in summer commonly exceed 30 C. Their cold tolerance is a more limiting factor. Most sources state USDA cold hardiness zone 7 as their limit, though reports exist of people growing them in zone 6. As for cold hardiness I would rate them as follows from most to least: Z. candida to zone 7, Z. carinata to zone 8 and finally Z. citrina to zone 9, perhaps 8b. With cold protection in winter you can probably push them further, or better yet container grow them so they can be brought in during the peak of winter.

Soil conditions are perhaps less of a problem, since all three can handle moderately acid to neutral conditions well. Organic based soils seem to work well for these, yet they are not picky, growing just fine in sands and loamy soils. They enjoy having moist roots, however they don’t need swampy conditions even though some species are found in wetlands. Of the three, Z. citrina seems the most adapted to drier soils, though all are tough customers once established. In the often waterlogged soils of Japan’s summer monsoon, I’ve found this species a bit difficult to grow long term, though both Z. candida and Z. carinata are easy here.

They will do best in sunny conditions, particularly if your summers are not overly warm, since they like warm soil. They do also seem to grow just fine in light shade, though flower count will probably be much less. At my house I’ve grown all three in moderately sunny conditions and have been rewarded with flowers year after year. These bulbs are the kind that you plant and forget about – they thrive on their own without any need of maintenance. Like Lycoris bulbs however, if you buy them in dried out condition, they will take a year or two to establish, so you may not get many flowers at first.

Luckily, they are quite adaptable to containers provided they have good drainage and adequate moisture. Avoid growing them as wetland or bog plants, especially in containers (though Z. candida can handle these conditions well). Propagation is by offsets or seeds. The seeds need to be planted soon after ripening, but are fairly easy to germinate and grow (especially Z. citrina, which self seeds on its own).

Pests are few, and since these bulbs contain a number of poisonous alkaloids, most creatures don’t mess with them. The fungal disease known as red blotch caused by Stagonospora curtisii (syn. Peyronellaea curtisii) can be a problem during cold, wet conditions. Still, rain lilies seem to ride through outbreaks easily even without treatment.

Zephyranthes bulbs contain a cocktail of alkaloids with cytotoxic effects. A number of species including Z. candida and Z. citrina have been used in traditional medicines for the treatment of a wide range of diseases such as cancer and diabetes. A number of these alkaloids have been found as effective inhibitors of various tumor lines in the laboratory. See these two articles outlining the alkaloids present in Z. citrina and Z. carinata (syn. grandiflora).

Zephyranthes are a genus of dwarf bulbs that are great for both warm temperate and subtropical gardens. Trouble free, self propagating, and lovely to the eye, these bulbs light up any garden in summer.