white-flowered leafcup

(Polymnia canadensis)

Conservation Status
white-flowered leafcup
Photo by Greg Watson
  IUCN Red List

not listed


N5 - Secure

SNR - Unranked


not listed


White-flowered leafcup is a large but little-known woodland wildflower. It occurs in the United States from Vermont to Georgia, west to Minnesota and Oklahoma, and in southern Ontario Canada. In Minnesota it is mostly restricted to the southeast corner of the state, where it reaches the northwest extent of its range. It is found in woodlands and forests. It grows under medium to light shade, in moist, loamy, limey (calcareous) soil.

White-flowered leafcup is an erect, perennial forb that rises on multiple stems from fibrous roots and usually also from underground stems (rhizomes). It sometimes forms colonies. It can be 20 to 70 (50 to 180 cm) tall, but in Minnesota it is usually no more than 48 (120 cm) in height. The stems and leaves are not fragrant when crushed.

The stems are erect or ascending and usually have several branches toward the top. The upper stem is moderately to densely covered with long, soft, straight or shaggy hairs, and also with gland-tipped or sticky hairs. The lower stem is hairless or nearly hairless.

The leaves are opposite and mostly 1½ to 8 (4 to 20 cm) long, and ¾ to 4¾ (2 to 12 cm) wide, on 1¼ to 3 (3 to 8 cm) long leaf stalks (petioles). The largest lower leaves are sometimes much larger, up to 16 (40 cm) long and 10 (25 cm) wide on up to 4¾ (12 cm) long petioles. The petioles are green or purplish near the base, grooved on the upper side, and covered with short, soft, glandular hairs. They are sometimes winged for a short distance but only near the blade. Larger leaves often have a rounded leaf-like appendage (stipule) at the base that wraps around the stem. Opposite stipules sometimes fuse together creating a short cup. This is the feature that gives the species its common name.

Lower leaf blades are rounded to heart-shaped or egg-shaped in outline and are often deeply cut into 5 to 7 lobes. They are mostly broadly tapered at the base. The lobes are sharply pointed at the tip. The upper surface is dark green and may be hairless or sparsely to moderately covered with short, soft, curved, sometimes gland-tipped or sticky hairs. The lower surface is pale green and is sparsely to moderately covered with short, gland-tipped or sticky hairs, especially near the main veins. The margins are finely to coarsely toothed. Upper leaf blades are smaller, triangular or egg-shaped, and mostly unlobed.

The inflorescence is a loose, branched, often spreading or nodding cluster of 2 to 5 flower heads at the end of the stem and branches. Each division of the cluster is subtended by a pair of modified leaves (bracts). Flower stalks (peduncles) are densely covered with glandular hairs. At the base of each flower head there is a 316 to (5 to 9 mm) long, ¼ to ½ (6 to 13 mm) in diameter, cup-like whorl (involucre) of 6 to 21 bracts (phyllaries) in two series. The phyllaries are moderately to densely covered with sticky or gland-tipped hairs on the outside. The inner phyllaries are egg-shaped to broadly inversely egg-shaped and are loosely ascending. The outer 2 to 4 phyllaries are lance-shaped to narrowly egg-shaped, slightly longer and narrower than the inner ones, and widely spreading or curved backward.

Each flower head has 5 to 8 ray florets and a central disc with 26 to 40 disc florets. The rays are sometimes reduced to just a minute tube with no flat, petal-like portion (ligule). When a ligule is present it is white, widely spreading, and small, 116 to (2 to 10 mm) long, with three rounded lobes at the tip. The disc florets have 5 petals fused at the base and for most of their length into a tube, then separated into 5 short lobes. The corolla is pale yellow and (3 to 4 mm) long.

Each ray floret is replaced by a single fruit. The fruit is a dry, (3 to 4 mm) long capsule (cypsela) with a single seed. The cypsela is dark brown to black, usually with some reddish mottling, and is bluntly 3-angled or sometimes ribbed.




20 to 70 (50 to 180 cm)


Flower Color


White ray florets, pale yellow disk florets


Similar Species


Moist. Woodlands, forests. Medium to light shade. Calcareous soil.




June to September


Pests and Diseases






Distribution Map



2, 3, 4, 5, 7, 24, 28, 29, 30.










  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  


Asterales (sunflowers, bellflowers, fanflowers, and allies)  


Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Asteroideae  





Subordinate Taxa






Polymnia canadensis var. radiata

Polymnia radiata


Common Names



pale-flowered leaf-cup

whiteflower leafcup

white-flowered leafcup

white-flowered leaf-cup










Modified leaf at the base of a flower stalk, flower cluster, or inflorescence.



Alkaline; rich in limestone; containing a high proportion of calcium carbonate.



A collective name for all of the petals of a flower.



A dry, one-chambered, single-seeded seed capsule, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed from the wall of the inferior ovary and also from other tissues derived from the receptacle or hypanthium, does not split open at maturity, but relies on decay or predation to release the contents.


Glandular hairs

Hairs spread over aerial vegetation that secrete essential oils. The oils act to protect against herbivores and pathogens or, when on a flower part, attract pollinators. The hairs have a sticky or oily feel.



A whorl of bracts beneath or surrounding a flower or flower cluster.



In grasses and sedges, a membranous appendage at the junction of the leaf and the leaf sheath, sometimes no more than a fringe of hairs. In flowering plants, the flat, strap-shaped, petal-like portion of the corolla of a ray floret.



In angiosperms, the stalk of a single flower or a flower cluster; in club mosses, the stalk of a strobilus or a group of strobili.



On plants: The stalk of a leaf blade or a compound leaf that attaches it to the stem. On ants and wasps: The constricted first one or two segments of the rear part of the body.



An individual bract within the involucre of a plant in the Asteraceae family.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.



A small, leaf-like, scale-like, glandular, or rarely spiny appendage found at the base of a leaf stalk, usually occurring in pairs and usually dropping soon.


Winged leaf stalk

A leaf stalk with a leaf-like or membrane-like extension along both sides.





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Greg Watson

    white-flowered leafcup      
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  Greg Watson

Location: Great River Bluffs State Park

white-flowered leafcup

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Created: 8/2/2022

Last Updated:

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