Nodding Onion

Nodding Onion Allium cernuum Lily family (Liliaceae) Description: This perennial plant consists of a tuft of basal leaves from which one or more flowering stalks emerge. The basal leaves are erect, ascending, or arching; they are up to 12" long and up to 8 mm. across. The basal leaves are linear in shape, medium green, glabrous, and smooth along their margins; they are solid and flattened. Leaf venation is parallel. Each leaf is slightly keeled along its midvein. The flowering stalks are up to 1½' long and more or less erect; they are light green or light reddish purple, glabrous, and terete. Each stalk terminates in a nodding umbel of flowers that emerges from a pair of sack-like membranes; these membranes are deciduous. Each umbel spans about 1½–2" across, consisting of 40-60 pedicellate flowers. The flowers are individually about ¼" (6 mm.) across, consisting of 6 spreading tepals, 6 exserted stamens, and an ovary with a style. The tepals are white, light lavender, or pink; they are lanceolate in shape. The stamens have white filaments and yellow anthers. The pedicels are ½–1" long; they are light green or light reddish purple, glabrous, and more or less terete. The blooming season usually occurs during mid-summer, lasting 3-4 weeks. There is no noticeable floral scent. Afterwards, the flowers are replaced by seed capsules; each capsule contains several small black seeds that it splits open to release. The root system consists of a bulb that is longer than it is wide. Both the bulb and foliage of this plant have a typical onion-like scent. Clonal offsets are produced, forming new bulbs underground. Cultivation: The preference is full to partial sun, moist to mesic conditions, and soil containing black loam, sand, or rocky material. While this plant can survive hot dry summers, it does better with more moisture. Foliar disease is rarely a problem. This plant is easy to grow under cultivation, and it will spread gradually under suitable conditions. It is easier to establish plants by transplanting the bulbs of offsets, rather than by attempting to germinate the seeds. Range & Habitat: Nodding Onion is an uncommon plant that occurs only in NE Illinois (see Distribution Map), where it is native. Habitats include black soil prairies, sandy pannes, and thinly wooded bluffs. Much of the prairie habitat where this plant once occurred has been destroyed by development. Nodding Onion is normally found in high-quality natural areas, although it could escape from cultivation into more disturbed areas. Faunal Associations: The nectar and pollen of the nodding flowers attract primarily bees, including honeybees, bumblebees, Anthophorine bees (Anthophora spp.), and Halictid bees (Lasioglossum spp.). Insects that feed destructively on the foliage, bulbs, and other parts of Nodding Onion and other onion species (Allium spp.) include the Onion Plant Bug (Lindbergocapsus allii) and a similar plant bug (Lindbergocapsus ainsliei), larvae of the False Japanese Beetle (Strigoderma arbicola), larvae of the Onion Maggot (Delia antiqua), larvae of the Black Onion fly (Tritoxa flava), larvae of the Onion Bulb Fly (Eumerus strigatus), and Onion Thrips (Thrips tabaci). Mammalian herbivores usually avoid Allium spp., although cattle and other livestock may browse on their foliage along with the grass in pastures, causing an off- flavor in their milk. Photographic Location: The photographs were taken at the wildflower garden of the webmaster in Urbana, Illinois, and at a restored prairie in Meadowbrook Park of the same city. Comments: This plant is easy to identify because of the nodding habit of its umbels of flowers. Nodding umbels of flowers are an evolutionary adaptation that tends to restrict insect visitors to bees. Other insects are more reluctant to hang upside down while attempting to feed on nectar or pollen. The nodding habit may also protect the nectar from rain. Compared to 2 other species that are native, the Cliff Onion (Allium stellatum) and Wild Garlic (Allium canadense), Nodding Onion (Allium cernuum) has wider leaves. Compared to the non-native Field Garlic (Allium vineale), Chives (Allium schoenoprasum), and Cultivated Onion (Allium cepa), the leaves of Nodding Onion are flattened and solid throughout, rather than hollow. Return Butterfly Milkweed Asclepias tuberosa Milkweed family (Asclepiadaceae) Description: This herbaceous perennial plant is 1-2½' tall. Young plants develop from a single central stem, while older plants tiller at the base, sending up multiple erect to ascending stems from a large taproot. These stems are unbranched below, becoming branched above where the flowers occur. The stems are light green to dull reddish purple, terete, and more or less covered with spreading hairs. Densely distributed along these stems, are alternate leaves that differ little in size. These leaves are 2½–3½" long and ½–¾" across; they are linear-oblong to lanceolate- oblong in shape, while their margins are entire (toothless). The tips of the leaves are acute, while their bases are slightly cordate, truncate, or rounded. The leaves are sessile, or they have short petioles up to 3 mm. long. The upper leaf surface is medium to dark green and glabrous to sparsely short-pubescent, while the lower leaf surface is light to light-medium green and mostly short-pubescent. Along the lower sides of the major veins, this pubescence is somewhat longer. The foliage of this plant lacks a milky latex. Usually several umbels of flowers develop from the upper stems and the axils of upper leaves. These umbels span 1–2½" across, consisting of 8-25 flowers each; they are slightly dome-shaped and often horizontally adjacent to each other. Each flower consists of 5 sepals, 5 petals, 5 hoods with horns, and a central reproductive column that is white to light green and short. The sepals are light green, hairy, and lanceolate in shape; they are largely hidden when the flowers open. The petals are more or less orange, lanceolate in shape, and declined (bent downward). The hoods are more or less orange, erect, and curved- ovate, forming open oblique tubes. The horns are more or less orange, sickle-shaped, incurved, and exserted from the hoods (one horn per hood). Usually the petals, hoods, and horns are orange, but sometimes they are reddish orange or yellowish orange. The pedicels are ¾–1½" long, light green or light reddish purple, terete, and more or less covered with spreading hairs. At the base of these pedicels, there are several spreading bracts up to 8 mm. long; they are green, linear-lanceolate in shape, and pubescent. The peduncles of the umbels are ½–2½" long, light green to dull reddish purple, terete, and hairy. The flowers bloom during early to mid-summer and sometimes a second time during late summer to early autumn. The flowers are relatively long-lasting, but they have no noticeable fragrance. Flowers that have been successfully cross- pollinated are replaced by follicles (seedpods that open along one side). These follicles are 4-6" long and ½–¾" across at maturity; they are initially light green, but later turn brown. The follicle surface is smooth and short-pubescent. These follicles eventually split open to release their seeds to the wind. Mature seeds are about 4 mm. long, flattened-oval in shape, brown, and narrowly winged along their margins; the apices of these seeds have large tufts of white hair. The root system consists of a woody taproot that is thick and knobby. This taproot can extend several feet below the ground surface. Cultivation: The preference is full sun, mesic to dry conditions, and an acidic soil that is sandy or rocky. However, this plant will adapt to other kinds of soil, including those that contain loam or clay, if they are well-drained. Although this plant develops somewhat slowly, it is easy to cultivate in open sunny areas once it becomes established. Tolerance to hot dry weather is excellent. If the taproot of a young plant is planted too close to the soil surface, it may become damaged by frost due to heaving of the soil. Range & Habitat: The native Butterfly Milkweed is occasional to locally common in Illinois, except for the western section of the state, where it is less common (see Distribution Map). Habitats include upland sand prairies, hill prairies, cemetery prairies, sandy savannas, open rocky woodlands, shale and sandstone glades (in southern Illinois), abandoned sandy fields, roadside embankments, and areas along railroads. Because of the showy orange flowers, Butterfly Milkweed is often cultivated in gardens. This milkweed is found in both disturbed areas and high quality natural areas. Occasional wildfires are probably beneficial in maintaining populations of this plant as this reduces competition from woody vegetation and taller herbaceous vegetation. Faunal Associations: The flower nectar attracts honeybees, digger bees (Melissodes spp.), leaf- cutting bees (Megachile spp.), Halictid bees (including green metallic bees), thread-waisted wasps (Ammophila spp.) and other Sphecid wasps, and butterflies, including Fritillaries (Speyeria spp.), Swallowtails (Papilio spp.), and the Monarch (Danaus plexippus); see Robertson (1929). The Ruby-throated Hummingbird is also attracted to the flowers. Some insects feed destructively on the leaves, flowers and buds, seedpods, and other parts of Butterfly Milkweed. These insects include larvae of the Blackened Milkweed Beetle (Tetraopes melanurus), the Small Milkweed Bug (Lygaeus kalmii), the Large Milkweed Bug (Oncopeltus fasciatus), larvae of a butterfly, the Monarch (Danaus plexippus), and larvae of a moth, the Unexpected Cycnia (Cycnia inopinatus). Butterfly Milkweed is the preferred host plant of the preceding moth (see Yanega, 1996; Betz et al., 1997; Wagner, 2005). A polyphagous insect, the Curve-tailed Bush Katydid (Scudderia curvicauda), was observed to feed on the leaves of this milkweed (Gangwere, 1961); it may also feed on the flowers. While the foliage of Butterfly Milkweed lacks the toxic milky latex that is typical of other milkweeds (Asclepias spp.), mammalian herbivores nonetheless appear to avoid it.

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