Narrowleaf Hawksbeard is an erect annual introduced and somewhat invasive plant, growing from 8 to 40 inches high on stems that branch, sometimes at the top only, sometimes from the lower stem. Stems are grooved, finely hairy and contain a milky juice.
The leaves are alternate and vary by position on the stem. A rosette forms first that resembles the common Dandelion rosette. Basal leaves are stalked and toothed to pinnately and unequally lobed, while the stem leaves are without stalks and decrease in size toward the top of the plant. These are linear to lanceolate, 4 to 5 times longer than wide. Upper stem leaves have entire margins while those below can have a few small teeth to a few small lobes that are backward turning. Margins edges can roll under toward the mid-rib (said to be revolute). The upper surface is smooth while the underside can be smooth or with dense very fine hair. Stem leaves have a thin auricle which clasps the stem.
The inflorescence resembles a panicle or corymb form at the top of the stem branches with around 5 to 20 stalked flower heads although a few plants have been known to have 100+.
The flowers are are ligulate, that is, with rays. There can be 30 to 70 ray florets, all bisexual and fertile, with yellow rays that are 10 to 13 mm long, longer than the phyllaries and toothed at the tip. The flower head is about an inch wide and is part way between being bell shaped and cylinder shape. Each floret has 5 stamens with yellow anthers that tightly surround the style, which is darker colored and has a 2-lobed tip. The outside of the head has 12 to 15 green phyllaries which are lanceolate in shape, 5 to 9 mm long, with pointed tips that are whitish. Their bases are keeled and thickened. The surfaces are hairy with the hair on the inner surface being very short and fine. Immediately below the phyllaries are shorter spreading calyculi, usually around 12 and also hairy, as are the flower stalks which also have several small bractlets on the stalk.
Seed: Fertilized flowers produce a dark reddish-brown cypselae (the seed) which has 10 ribs, is 3 to 4 mm long and narrow, tapered on both ends. There is a soft extensive white pappus attached for easy wind dispersion. Seeds do not need a dormant period for germination. Studies have indicated a single plant can produce over 49,000 seeds (Royer and Dickinson 1999).
Habitat: Narrowleaf Hawksbeard has a slender but deep taproot, growing in waste places, woodland clearings, and recently disturbed sites; it grows on a diversity of soils, but prefers lighter soils. it can be found almost anywhere where there is sun and moisture. It regenerates solely by re-seeding.
Names: The genus Crepis is derived from the Greek krēpis, meaning 'a boot' or 'a sandal' which is no longer clear, but may allude to the shape of the cypselae. It was also the name of a plant in the writings of Theophrastus. The species name tectorum refers to the roofs of houses. When Linnaeus assigned names he used this word for a number of plants that he found growing on the thatched roofs of houses in Sweden. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: There are 24 species of Crepis found in North America and around 200 world wide. C. tectorum is differentiated by being an annual; having phyllaries with a keeled base and fine hair on their inner surfaces; and the dark reddish-brown cypselae. A close relative is C. biennis, not found in Minnesota, which is biennial; has cypselae that are yellowish to reddish-brown and longer - 4 to 7mm; and the inner phyllary surface has matted whitish hairs. What is found in Minnesota is C. runcinata var. runcinata, the Fiddleleaf Hawksbeard, where the basal leaves, resembling a fiddle shape, are entire or weakly lobed, and the stems is smooth. The plant may also be confused with Rough (or narrow-leaf) Hawkweed, Hieracium umbellatum, but that plant is taller, usually not branched below the inflorescence, a perennial, fibrous rooted, the phyllaries are dark-green to reddish without a keeled base. Young seedlings of C. tectorum resemble those of the sow thistles and of Prickly Lettuce, Lactuca serriola, but the later true leaves do not.
Above: Narrowleaf Hawksbeard can have much branching from the lower part of the plant as seen here. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: The flowers have ray florets only, 30 to 70, which open from the outside rows toward the center. Rays have toothed tips. Stamens have yellow anthers and tightly surround the darker style.
Below: 1st photo - Flower nearing full development. 2nd Photo - seed head.
Below: leaves are narrow with pointed tips and of reducing size toward the stem top. Lower leaves can have small to larger teeth that are backward curving. Stem leaves clasp the stem with a pair of auricles.
Below: 1st photo - The underside of the leaf is paler in color and can have dense fine hair. Note the rolled leaf margin. 2nd photo - Seeds are a dark reddish-brown cypselae, 3 to 4 mm long, narrow, with 10 ribs, tapered on both ends.
Below: 1st photo - The upper phyllaries number 12 to 15 with pointed tips that are whitish and a darker green keeled base, hairy. Below are the calyculi, shorter, spreading outward and also hairy. Below the head on the stalk is one of the bractlets. 2nd photo - The stem is grooved, finely hairy. Note the narrow pointed auricle of the leaf.
Notes: It is uncertain when Narrowleaf Hawksbeard entered the Garden. It was not listed by Martha Crone on her 1951 census but did appear on the 1986 and 1990 census - probably wind delivered from nearby property.
Narrowleaf Hawksbeard was introduced from Siberia prior to 1890 and is found in most of North America above the 38th parallel including the far north of Alaska and Canada. In Minnesota it is found in most counties except those of the southwest quadrant and along the Dakota border. In that distribution it is almost the opposite of the only other Crepis species found in Minnesota, the native Fiddleleaf Hawksbeard, C. runcinata var. runcinata.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"