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    Epilobiums are often difficult to identify because many of them are interfertile, i.e., they hybridize readily, or as Intermountain Flora states, there is "rampant hybridization in... Epilobium".  Therefore, Intermountain Flora indicates, in about half of the species in our area, "specific distinctions are... vague".  The two species shown below are in this vague group and are highly variable in many of their growth characteristics.

    Linnaeus named this genus in 1753; the word "Epilobium" is from the Greek for "upon a capsule" and refers to the long tubular inferior ovary, shown extending to the left of the pinched area in the left center of this photograph of Epilobium ciliatum.

Epilobium ciliatum

 

Epilobium ciliatum
Epilobium ciliatum (Willowherb)
Onagraceae (Evening Primrose Family)

Foothills, montane. Roadsides, meadows. Summer.
Prater Ridge Trail, Mesa Verde National Park, August 13, 2005.

Epilobium ciliatum can grow in both moist and dry conditions, it can be two-to-six feet tall or just eight inches tall, and it is equally variable in leaf shape, amount of branching of the stem, and other characteristics.  Even the silky fluff that carries the seeds can vary  --  from white to dingy.

The picture at left shows just the lower few inches of a plant over two feet tall.  Leaves are very minutely toothed and stems often reddish.  

Constantine Rafinesque named this species in 1808.  The species has had several dozen other names since then.  "Ciliatum" is Latin for "hairy" and botanically refers to fine, marginal hairs  --  which can be seen as a silvery glow along the edges of some of the seed pods and buds in the two pictures below.

 

Epilobium ciliatum 
Epilobium ciliatum (Willowherb)
Onagraceae (Evening Primrose Family)

Foothills, montane. Roadsides, meadows. Summer.
Prater Ridge Trail, Mesa Verde National Park, August 13, 2005.

Pink flowers are most common for Epilobium ciliatum but white is almost as common and both pink and white flowers can appear on the same plant.

Epilobium ciliatum
Epilobium ciliatum
Epilobium ciliatum (Willowherb)
Onagraceae (Evening Primrose Family)

Foothills, montane. Roadsides, meadows. Summer.
Prater Ridge Trail, Mesa Verde National Park, August 13, 2005.

The long, vertical seed pods shown in the above left picture will soon ripen and split in graceful arches exposing the soft tuft of hairs that are attached to and carry aloft the tiny, brown, minutely ridged seeds.

Epilobium hornemannii (Willowherb)
Onagraceae (Evening Primrose Family)

Montane, subalpine. Meadows, streamsides. Summer.
Kilpacker Trail, August 1, 2000.

Epilobium hornemannii flowers are tiny, pink/white/light-blue, and inconspicuous, but the plant is so common that it eventually attracts attention.  The pictured specimen is lush; other Epilobium hornemannii (see below) may have far fewer and narrower leaves, fewer stems, and be shorter.  Epilobium hornemannii is a highly variable plant.

Exact identification is even more problematic since, as observed above, it also hybridizes .  For instance, E. Hornemannii hybridizes readily with E. lactiflorum which occupies similar habitat as E. hornemannii and, according to William Weber, can be distinguished from E. hornemannii by its "several broad withered leaves [at the base of the stem] at flowering time."  E. hornemannii has "small and inconspicuous or no withered leaves" at flowering time.

Look for Epilobium hornemannii along moist montane and sub-alpine trails, near ponds, and along irrigation ditches.  It is common for Epilobium hornemannii to have red stems and leaves in the spring and to return to these colors in the fall.

Heinrich Reichenbach (1793-1879) named this species in 1824.  Jens Hornemann was a Danish botanist of the early 1800s. (More biographical information.)

Epilobium hornemannii
Epilobium hornemannii (Willowherb)
Onagraceae (Evening Primrose Family)

Montane, subalpine.  Meadows, streamsides. Summer.
Groundhog Meadow Trail, July 31, 2004.

Epilobium hornemannii
Epilobium hornemannii (Willowherb)
Onagraceae (Evening Primrose Family)

Montane, subalpine.  Meadows, streamsides. Summer.
Groundhog Meadow Trail, July 31, 2004.

Epilobium hornemannii
Epilobium hornemannii (Willowherb)
Onagraceae (Evening Primrose Family)

Montane, subalpine.  Meadows, streamsides. Summer.
Colorado Trail near Kennebec Pass, August 12, 2004.

Epilobium hornemannii seed capsules (the dark vertical tubes in the lower and upper right) split in graceful arches (center) and the brown seeds imbedded in tiny white fluff are ready for a breeze.

Epilobium hornemannii
Epilobium hornemannii (Willowherb)
Onagraceae (Evening Primrose Family)

Montane, subalpine.  Meadows, streamsides. Summer.
Colorado Trail near Kennebec Pass, August 12, 2004.

Epilobium hornemannii seed capsules (the dark vertical tubes in the lower and upper right) split in graceful arches (center) and the brown seeds imbedded in tiny white fluff are ready for a breeze.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Epilobium ciliatum

Range map for Epilobium hornemannii

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