Wood-poppy (Stylophorum diphyllum) COSEWIC assessment and status report: chapter 3

Species Information

Name and classification 

Scientific name:
Stylophorum diphyllum (Michaux) Nuttall
Synonyms:
Chelidonium diphyllum Michaux; Meconopsis diphylla DC
Common names:
wood-poppy, celandine poppy, mock poppy, yellow poppy
Family:
Papaveraceae (Poppy Family)
Major plant group:
Eudicot flowering plant
Type specimen:
Lectotype species: Paris?

Stylophorum diphyllum, the only North American representative of the genus, was originally described by Michaux (1803) as a species of Chelidonium and was transferred to Stylophorum by Nuttall (1818). Vegetatively it is similar to the Old World species Chelidonium majus, and was reunited with Chelidonium by Prain (1895).

Morphological description 

Stylophorum diphyllum is a hairy, perennial herb up to about 40 cm tall, developing a stout rhizome. Stems, sepals, and sometimes leaves, have few to many stout, multi-cellular hairs. The leaves are pale beneath, mostly basal, with long petioles. They are deeply pinnately divided, almost or quite to the mid-vein, into 5-7 irregular lobed or toothed segments. Flowers are in few-flowered clusters subtended by 2 or 3 more-or-less opposite leaves. The two sepals are hairy and slightly fleshy. The four petals are 2-5 cm long and rich yellow. The stamens are numerous with very slender filaments and oblong anthers. The ovary is densely pubescent, more or less elliptical in shape and narrowed to a long style, which is persistent in the fruit. The fruit is a nodding, greyish-green, soft-bristly, pubescent capsule, splitting by longitudinal clefts into 3 or 4 segments (Gleason, 1952; Ernst, 1962). All parts of the plant have a yellow to orange, bitter-tasting sap. A technical description of the species is given in Gleason and Cronquist (1991).

Line drawings of Stylophorum diphyllum leaf and flower are given in Gleason (1952). More detailed anatomical drawings appear in Ernst (1962). A colour plate is given in Boynton (1918). A drawing by Susan A. Reznicek illustrates an article by A.A. Reznicek (1988). Drawings from sketches made in the field by the senior author are given in Figure 1.

Figure 1. Line drawing of Stylophorum diphyllum by Jane Bowles.

Figure 1. Line drawing of Stylophorum diphyllum by Jane Bowles.

During early spring, the large bright yellow flowers of Stylophorum diphyllum are distinctive and attract attention from some distance. At this season the pubescence is also very obvious as are the pale backs of the leaves. In its vegetative state Stylophorum diphyllum is strikingly similar to the relatively common adventive species from the Old World, Chelidonium majus (greater celandine). In Chelidonium majus the leaves are all alternate. In Stylophorum diphyllum there are one or more basal leaves, with opposite or whorled leaves present on the otherwise naked flowering stem. The flowers of Chelidonium majus are much smaller, with narrower petals only about 1 cm long, and glabrous sepals and capsules. The capsule of Stylophorum diphyllumis ovoid and bristly-hairy whereas that of Chelidonium majus is hairless and linear-cylindric.

Genetic description 

Stylophorum diphyllum reproduces sexually and appears to be capable of both outcrossing and selfing. The degree of genetic diversity among and within Stylophorum diphyllum populations is being determined through the application of molecular genetic markers. This is a work in progress, but early results suggest variation both within and among Canadian populations and differences between Canadian and U.S. populations (Gharebaghi, 1996; Galbraith, pers. comm., 2005). The distance between populations and the unstable nature of the intervening habitat suggests significant barriers to genetic exchange among populations. 

Designatable units 

Stylophorum diphyllum in Canada forms a single designatable unit since the populations occur in close proximity and in the same COSEWIC ecological area (Great Lakes Plains).

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