Onagraceae

Onagraceae – Evening Primrose Family 

About 20 genera and 650 species of Evening Primrose occur world-wide.[i] Simple, pinnately veined leaves can be opposite, alternate, whorled, or all basal.[ii] Members of the genus Epilobium, common to the West Eugene Wetlands, have opposite leaves lower down on the stalk and become alternate further up the plant.[iii] Onagraceae inflorescences are variable and can be spikes, panicles, or solitary flowers. The delicate blossoms of this family have four sepals and four petals fused into a floral cup (hypanthium).[iv] Onagraceae can have an equal number or twice as many stamens as petals. Inferior ovaries mature into a long, dry capsules comprised of four many seeded chambers containing many fluffy wind dispersed seeds.[v]

  

Epilobium desniflora – Dense Spike Primrose

EPDE.jpgSpecies Code: EPDE

Growth Habit: Erect annual forb growing 30 to 100 centimeters tall, central stem single or somewhat branched, covered with tiny hairs, and small attractive flowers emerging from axils of upper leaves.

Leaves: Except for near the base of the plant where leaves are opposite, most are alternately arranged. All leaves are sessile (attached directly to the stem), with lower leaves being lance-shaped and 1.5 to 5 centimeters long.[vi] Dense upper leaves are oval to lance-shaped, with subtle teeth on the margin.[vii]

Flowers: Colorful inflorescences are arranged in crowded spikes nestled in leaf axils. Four bright pink (sometimes white) petals form a 1.5 to 4 mm long floral tube with green calyx lobes 2 to 9 mm long.[viii]

Fruits: Produces 1 to 2 mm, glabrous, wind dispersed seeds within 4 to 11 mm long capsules.[ix]

Ecology: Facultative Wetland Species (FACW), a Hydrophyte that occurs mostly in sites that are wet in spring but dry by late summer and tolerates dryer areas.[x]

Chamerion angustifolium (formerly Epilobium angustifolium) – FireweedEPAN

Clarkia amoena ssp. Lindleyi – Lindley’s ClarkiaCLAM

Clarkia purpurea ssp. Quadrivulnera – Wine Cup ClarkiaCLPUPA

Epilobium brachycarpum –  Tall Willow HerbEPBR

Epilobium campestre –  Small Willow Herbepca

 

 

 

[i] Simpson, M. Plant Systematics 2nd ed. Academic Press, Burlington, MA. 2010. 353.

[ii] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 272.

[iii] City of Eugene, Seed Collection Maual, Epilobium densiflorum, 2009.

[iv] Simpson, M. Plant Systematics 2nd ed. Academic Press, Burlington, MA. 2010.

[v] Elpel, T. J., Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, 2004. 99.

[vi] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001.

[vii] Guard, J. (1995). Wetland Plants of Oregon and Washington. Lone Pine Publishing, Edmonton, Alberta. 104. 118.

[viii] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 276.

[ix] City of Eugene, Seed Collection Manual, Epilobium desniflorum, 2009.

[x] USDA Plants Database: <https://plants.usda.gov/core/profile?symbol=EPDE&gt;