Evening rain-lily (Cooperia drummondii, also known variously by some athorities as Cooperia chlorosolen or Zephyranthes chlorosolen) of the Amaryllis (Amaryllidaceae) family, formerly of the Lily (Liliaceae) family, occurs in the south-central United States from New Mexico to Kansas to Alabama and then thence south to the Gulf Coast and into Mexico. In Arkansas, it is recorded from five counties scattered in the western portion of the state and is considered of “conservation concern” by the Arkansas Natural Heritage Commission. It is currently the only species of the Cooperia genus known from the state. The specific epithet recognizes Thomas Drummond, an 18th century Scottish naturalist that first discovered this species. Other common names are “cebolleta” (a Spanish word alluding to the plant’s vegetative resemblence to onions [cebollas]) and Drummond’s rain-lily. This species is found in prairies, glades, savannahs and woodland margins in a wide variety of dry to moist soils and in varying sunlight situations. Evening rain-lilies are perennial, herbaceous, bulbous plants that germinate with a single seed leaf or cotyledon (placing them in the class of flowering plants familiarly called monocots). The species has “true bulbs” which have a basal plate (caudex) that produces new roots annually, leaves, flower stems and lateral bublets.* Its life cycle during the temperate months is responsive to rainfall patterns; especially in late summer, hence the common name “rain-lily.”
Leaves continually grow within the bulb at the center of the basal plate with the most immature leaves at the center of a “leaf core.” Leaves appear at the surface, somewhat erratically, in response to air temperature and soil moisture. Leaves are most numerous in spring (without any associated flower stems), absent during hot dry summer months and may appear intermittently during the summer and fall (after flower stems appear in response to rain). Leaves have long, smooth, narrow, grey-green blades that may be 12 or more inches long and ¼ inch wide, with rounded tips. Leaves are in-folded along their entire length (more so near their bases) as a result of having been tightly pressed against other leaves during development within the bulb. Leaves tend to be somewhat twisted and lax, almost floppy.
Each leaf consists of an above-ground blade and an underground conical white base for water and nutrient storage that is concentric around the leaf core of the bulb. Bases are tightly overlapped and are pushed away from the center of the bulb as new leaves develop. With leaf bases being thicker at their mid-section, bulbs become rounded in lateral as well as vertical cross-section. Outermost leaf bases become thinner to a brown, tissue-like tunic before eventually disintegrating.
Photo 1: The twisted and somewhat floppy leaves of evening rain-lily seen in this early April photo grow in clusters from tips of bulbs and bulblets. Each leaf has a thick white base that encircles the bulb’s core of immature leaves.
Flowering occurs sporadically in summer into fall months several days after significant rainfall. A bulb produces one flower stem at a time. Flower stems originate from the basal plate between two leaf bases close to the leaf core. The stems follow the curvature of these two confining leaf bases to emerge at the top of bulbs, slightly off-center (leaves being at the center). Flower stems are pinkish at first, but become mostly green with the approach of anthesis. Upon emergence, the upper portion of the stem is covered by a bluntly pointed spathe that is the same color as the overall stem. The lower end of the spathe joins the stem immediately below the ovary, which is located up to 7 inches below the perianth (corolla + calyx) that emerges from within the spathe. Stems are slender, round to flattened, and hollow. Stems, which may be 12 or more inches long and weakly erect, are smooth and mostly equidimensional their entire length. The spathe peels back to below the ovary and quickly dries.
When a larger bulb is cut laterally at mid-bulb, along with prominently displayed concentric leaf bases, small flattened ellipses squeezed between leaf bases can be seen. These ellipses, lined up along an axis across the bulb, are either stems that have already produced seed (these are flattened brown ellipses) or would have produced stems at a later flowering episode (these are light colored ellipses). With a bulb producing one flower at a time, the sequence alternates from one side of the leaf core to the other.
Photo 2: Bulb-section at center of photo is lower half of a bulb while upper half of same bulb is arranged radially from ‘A’ through ‘O.’ ‘A’ is the leaf core composed of a half-dozen variably immature leaves at the bulb’s center (corresponding to the portion indicated with the arrow on the cross-section). Numbers ‘1’ through ‘5’ indicate stem sites with ‘2’ corresponding to ‘D’ (a wilting flower stem). ‘O’ represents the outer tunic.
Photo 3: In this mid-August photo, stems emerge after significant rainfall. Spathes recede as flowers continue to grow. Arrows point to ovaries.
Flowers gradually open in the evening several days after rainfall and remain open a day or two. Flowers, about 2 inches wide, have three mostly white sepals and three almost identical petals (together referred to as tepals) with a somewhat elongated ruffled oval shape. Tepals are of equal size and shape with a white upper surface along with lighter longitudinal veins. Sepals have pinkish beaks (remnants from when in bud) at their apices with that pinkish color extending partially down their lower sides. Flowers have six stamens with elongate, equal-sized anthers on short, down-bent filaments that position anthers close together and vertically so that the lower ends of the anthers are within the flower’s throat. Filaments are attached (adnate) to the tepals’ base just above the lower ends of the anthers. Pistils, up to 7 inches long, are free-standing from the inferior ovary, up the exceeding long tubular perianth (envelope surrounding sexual organs) with the stigma hidden immediately below the lower ends of anthers.
Photo 4: At full bloom, stems remain pinkish near their bases and above the ovaries (arrow). Note new leaves emerging at base of stems.
Photo 5: Elongate, upright anthers surround and hide the stigma. Three petals are positioned between three sepals. Note beaked sepals of flower and buds.
Flowering stems emerge, flower, and then produce seed over about an 8-day period. With fertilization, the perianth quickly wilts and dries, but may remain on the ovary until seed capsules mature. Ovaries enlarge to form a prominently three-chambered (trilocular) stubby capsule. With bulging chambers, capsule width equals the length. As the capsule dries, the top shrinks back to expose thin, shiny black, papery seeds in loosely layered stacks. Seeds readily fall from the opened chambers with slight movement of the capsule. The plant is a reliable vigorous seed producer due, perhaps, to the close contact of anthers and stigma along with the services of pollen-eating insects.
Photo 6: Seed capsules are composed of three bulging chambers. Flat papery seeds are loosely stacked within each chamber. Note dried perianth remaining attached to green capsule on left.
For a sunny moist to dry garden or natural area, evening rain-lily can surprise a person with the sudden appearance of flowers. The flowers are eye-catching as are the seed capsules. Along with multiplying via offset bulblets, many additional seedling plants should be expected. Seedlings can be controlled by removing capsules prior to maturing.
* Plants that store water and nutrients in fleshy underground structures to survive cold or dry conditions in a dormant state are called “geophytes.” In addition to bulbs, other geophytic structures are corms, tubers, tuberous roots and rhizomes.
Article and photographs by ANPS member Sid Vogelpohl
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