Know Your Natives – Aniseroot

Aniseroot (Osmorhiza longistylis) of the Carrot (Apiaceae) family is a herbaceous erect perennial that has pleasantly aromatic roots. It occurs across most of the U.S. from New Mexico to Montana, thence east to the Gulf and Atlantic Coasts, with the exception of Louisiana and Florida. In Arkansas, the species occurs in the Highlands of the northwestern half of the state and on Crowley’s Ridge. The genus name is from Greek words for “aromatic root”. The specific epithet is from Latin for “long-styled”. Other common names include sweet anise, long-style sweet-cicely, and smooth sweet-cicely*. It occurs in moist deciduous woodlands with light to moderate shade in soils enriched with decaying plant material.

Plants have thick, branching tap roots that terminate in long fibrous roots. Crushed roots have an anise scent.

In spring, new buds sprouting from the caudex (stem base) develop into basal leaves and a compressed mass of developing stems, leaves and inflorescences. Fully developed basal and cauline leaves have three pinnate leaflets that may be further pinnately divided into sub-leaflets (ternately pinnate to bipinnate). At the end of the growing season, stems decay while basal leaves may become ground-hugging and persist into spring.

Photo 1: In this early January photo of branching taproots, previous year’s basal leaves persist (extending off top of photo) and buds for new growth can be seen on caudex.
Photo 2: In this early April photo, a mass of developing stems, leaves and inflorescences emerge at center of plant. The large basal leaves are bipinnately compound, as are cauline leaves that will develop later.

Above the basal leaves, mature plants have one or two erect, typically pilose (densely short-pubescent), solid stems that grow to a height of about 2½ feet. Nodes are rather swollen and bear single cauline leaves which may subtend lateral or floral branches. Stems are a light green with lower portions and areas near nodes sometimes purplish. 

Photo 3: Immature ternately bipinnate leaf has a clasping base from which a compound umbel (with white flowers) has grown along with a lateral branch that bears another developing umbel (hanging down). Photo – April 15.

The compound leaves, to about 9 inches long and 12 inches wide, are divided into three principal sections (ternately compound). Leaflets have thin, rather flimsy blades with prominent irregularly wavy (sinuate) margins. They are a dull light to medium green on both surfaces. Stalks of leaves and leaflets are rounded on their upper side and flattened and grooved beneath. Crushed leaves have a light anise scent. 

Photo 4: This plant has two ascending basal leaves and two well-developed, cauline leaves, of which the uppermost subtends a peduncle with white flowers in a compound umbel. Note fine pubescence along purplish stem.

Inflorescences, flowering in mid-spring, are terminal and axillary compound umbels, consisting of one or two slender peduncles about 2 inches long. These terminate in three to six rays, each tipped by 5 to 17 pedicels supporting the umbellets of flowers. Rays are subtended by an involucre of 1-6 bracts, the umbellets by an involucel of 4-6 bractlets. Umbellets bear about 5-17 flowers, of which 5-7 are perfect (having both pistils and stamens), typically arranged around the perimeter of the umbellet, and the rest staminate. Flowers bloom in quick sequence from the outside toward center of umbellets so that fruiting begins while staminate flowers remain at anthesis.

The perfect flowers have no sepals, five white petals, five stamens, and a pistil of two united carpels with two free styles. As flowers open, stamens are curved inward before becoming erect. Stamens and knob-like anthers are initially white, but anthers become light tan as pollen develops. Styles have an enlarged base, the stylopodium, a characteristic of most species in the carrot family. The inferior ovary bears white hairs along longitudinal ribs, similar to the ciliate hairs of the floral bracts. The open corolla is ⅛ inch wide; the ovary at its tip, just below the corolla, is about 1/16 inch wide.

Staminate flowers, about 1/16 inch wide, have more slender pedicels and small bowl-shaped receptacles. Petals and stamens of staminate flowers are similar to those of the perfect flowers, however, the petals remain crimped together–the corolla does not flare outward.

Photo 5: This compound umbel has four umbellets of which the lower three have perfect and staminate flowers while the upper umbellet has staminate flowers only. Stigmas are held well above corollas. Note ciliate pubescence of bracts and bractlets and the ribbed ovaries.

Ovaries that are fertilized mature into long (to 1 inch) slender dry fruits called schizocarps that split into two 1-seeded halves called mericarps. These are slightly flattened and have longitudinal ribs with stiff forward-appressed hairs. Styles are persistent on the mericarps as spiny projections. At maturity, mericarps separate from each other and from the central axis so that only their tips cling to the tip of the central axis. At full maturity, black mericarps are slightly curved with a long spiny proximal tip and a short spiny distal tip (the persistent style). As various animals or birds brush against plants, the spiny tips and side-hairs become entangled in fur and feathers, providing seed dispersal.

Photo 6: In mid-June, schizocarps have split into two mericarps that cling to tips of the central axes. Upper leaf section shows adaxial surface while lower leaf section shows abaxial surface. Dried remnant is the third leaf section. (Parts separated for photo.)

For a native plant garden or natural area with moist soil and partial shade, this non-showy perennial may add extra texture and help in-fill an area. This perennial member of the carrot family does not seem to self-seed agressively. Roots, flowers and leaves are edible in salads or as a garnish.

Fifty-five species of the Carrot family occur in Arkansas, of which a number have bipinnate leaves and compound umbels. Characteristics of aniseroot that aid in its identification include: 1) a perennial species, 2) branched tap roots that have an anise scent, 3) broad leaves with bluntly toothed leaflets, 4) short dense pubescence along stems, 5) umbellets with perfect and staminate flowers, 6) petals of perfect flowers that have clawed tips, and 7) linear fruits. Aniseroot can be separated from the only other Arkansas species in the genus, hairy sweet cicely (Osmorhiza claytonii), by aniseroot’s 1) shorter, less conspicuous pubescence, 2) styles that extend outside corollas, 3) fruits that have prominent spiny hairs on longitudinal ribs, and 4) a stronger anise scent.

Article and photographs by ANPS member Sid Vogelpohl

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