Epilobium coloratum (Purple-leaf Willowherb)

Plant Info
Also known as: Cinnamon Willowherb, Eastern Willowherb
Genus:Epilobium
Family:Onagraceae (Evening Primrose)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; wet; marshes, swamps, bogs, fens, shores, river banks, ravines, swales, wet prairies, wet woods
Bloom season:July - October
Plant height:12 to 40 inches
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 4-petals

[photo of flowers] Flowers are single at the top of the stem and arising from leaf axils in the upper half of the plant. Flowers are white to pink, ¼ to 1/3 inch across with 4 notched petals. In the center is a white club-shaped style surrounded by 8 stamens of varying lengths.

[photo of sepals, buds and hairs] The 4 sepals cupping the flower are narrowly oblong-elliptic and shorter than the petals; in bud, the sepal tips are usually distinct and may flare out some. Flower stalks are short, less than ½ inch long. Between the flower and stalk is a slender ovary about an inch long and slightly wider than the stalk. The sepals, stalk and ovary are all variously covered in short, curved hairs, the hairs sometimes in lines; a few gland-tipped hairs may be mixed in.

Leaves and stems: Leaf attachment: alternate Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are mostly opposite though usually alternate on the upper stem, mostly narrowly lance-oblong, 1½ to 5 inches long, ¼ to about ¾ inch wide, often with a long taper to a pointed tip, and short-stalked. Edges are irregularly toothed, the teeth mostly crowded and the space between them (sinus) usually well-rounded. Color is dull green, sometimes with purple spots.

[photo of hairs on upper stem] Leaves on the lower plant are hairless, those nearer the flowers may be sparsely covered in short, curved hairs especially along the midvein, and may be mixed with sparse gland-tipped hairs. Stems are usually single, many-branched taking on a bushy appearance, green to purple or purple-spotted, especially at the leaf nodes. The lower stem is hairless, the upper stem variously covered in short, curved hairs, often in lines running down from the leaf stalk (decurrent), and may be mixed with sparse gland-tipped hairs. Vegetative buds (turions) are not produced.

Fruit: Fruit type: capsule/pod Fruit type: seed with plume

[photo of fruit] The ovary elongates up to about 3 inches as it matures, drying to brown then splitting lengthwise from the top down in 2 to 4 segments, the sides curving away and releasing the numerous seeds. Seeds are somewhat cone-shaped, brown, about 1.5 mm long, the surface covered in minute bumps (papillose); at the tip is a tuft of long, cinnamon-colored hairs to carry them off in the wind.

Notes:

Purple-leaf Willowherb is a common species found in all manner of wet places from southeastern Minnesota through the central and northern parts of the state. The Minnesota Willowherbs can be split into 2 groups, based on whether leaves are toothed or not. The toothed group includes natives Fringed Willowherb (E. ciliatum) and Purple-leaf Willowherb (E. coloratum). A third species, the non-native Great Hairy Willowherb (E. hirsutum) is not known to be in Minnesota but is present in Wisconsin and may eventually naturalize here; it has much larger, purplish pink flowers with a 4-parted style and leaves are all stalkless and mostly clasping.

Distinguishing the two natives can be something of a challenge. The most distinct characteristic between E. ciliatum and E. coloratum is the color of the hairs on mature fruit: E. ciliatum is white and E. coloratum is cinnamon-colored, though is quite pale when immature. If mature fruit or hairs are not available some combination of more subtle characteristics may lead to a positive ID:

  • E. ciliatum tends to be less bushy than E. coloratum.
  • E. ciliatum leaves are commonly more egg-shaped with a blunt tip and are somewhat shiny, especially when young, where E. coloratum leaves are commonly more narrowly lance-oblong with a pointed tip, often with a long taper to the tip, and have a dull surface.
  • The teeth on E. ciliatum leaves are little more than tiny glands, tend to be widely spaced (but not always), and the sinus between teeth is flattish to slightly concave, where E. coloratum teeth are more irregular, usually closer together and the sinus deeper and usually well-rounded (but not always).
  • E. ciliatum midstem leaves are stalkless or minutely stalked, those of E. coloratum are usually all distinctly short-stalked.
  • E. ciliatum flower buds are usually rounded at the tip, the sepal tips not dramatically distinct, where E. coloratum sepal tips are pretty distinct, and may even flare out a bit.
  • E. ciliatum tends to bloom 2 to 4 weeks earlier than E. coloratum; we noted E. ciliatum blooming in late June and E. coloratum in mid to late July. Both may bloom through September.
  • The hairs on E. ciliatum tend to be a mix of straight and curved hairs where E. coloratum hairs are mostly curved; glandular hairs are more numerous on E. ciliatum than E. coloratum, especially on sepals and ovaries.
  • E. ciliatum seeds are minutely grooved in lines and have a short neck (beak) between the tip of the seed and the hairs, where E. coloratum seeds are covered in tiny bumps (papillose) and have no beak.
  • E. ciliatum may produce vegetative buds (turions) where E. coloratum does not.
  • Some references note that the leaf veins of one of these are quite conspicuous and the other not so much, but there are conflicting reports and we have not found this to be a reliable distinction. The main lateral veins can be prominent on both.

Most of these traits are variable and differences can sometimes be very subtle, so when in doubt inspect multiple specimens to get a consensus. A hand lens can be very helpful.

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More photos

Photos by K. Chayka taken in Anoka and Ramsey counties. Photos by Peter M. Dziuk taken in Anoka and Sherburne counties and in his garden.

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