Iris tenax

Coastal strandCommon name Oregon Iris, or Toughleaf Iris


Occurs predominately on the coasts of Oregon and Washington, occasionally occurs in Northern California

Climate, elevation

Prefers a coastal climate

Occurs from 100m – 500m

Local occurrence

Common and widespread in most of western Oregon and southern Washington west of the Cascade Mountains. There is a separate race in the Klamath Mountains of northern California.

Habitat preferences

Prairies and pastures, open oak and coniferous forests

Plant strategy type/successional stage

Seral: perennial herb

Associated species

Lonicera ciliosa, Lonicera hispidula, Corylus cornuta, Crataegus douglasii var. suksdorfii, Fragaria chilonesis, Carex obnupta

May be collected as:

Seed, divisions

Collection restrictions or guidelines

Seeds easily collected from the large capsules

Seed germination

Seeds germinate with ease

Seed life

Not available

Recommended seed storage conditions

Stored seed should be sown as early in the year as possible in a cold frame

Propagation recommendations

The plant prefers acid and neutral soils. It can grow in semi-shade (light woodland) or no shade. It requires dry or moist soil and can tolerate drought.

Soil or medium requirements

It prefers light (sandy) and medium (loamy) soils and requires well-drained soil

Installation form

Seed - pick out the seedlings into individual pots when they are large enough to handle and either put them in a greenhouse or cold frame for their first year. Plant out into their permanent positions in late spring or early summer.

Divisions - Best done in early September after flowering but it can also be done in March. Larger clumps can be replanted direct into their permanent positions. Pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the spring.

Recommended planting density

9in – 15in spacing

Care requirements after installed (water weekly, water once etc.)

Water regularly; do not overwater

Normal rate of growth or spread; lifespan

Perennial with a moderate growth rate

Grows to 1 meter high by 1 meter wide  

Sources cited

  1. Plants for a Future - http://www.pfaf.org/database/plants.php?Iris+tenax
  2. Flora of North America - http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101717
  3. Dave’s Garden - http://davesgarden.com/pf/go/80105/
  4. USDA Plant Database - http://plants.nrcs.usda.gov/cgi_bin/topics.cgi?earl=plant_attribute.cgi&symbol=IRTE
  5. Society for Pacific Coast Iris - http://www.pacificcoastiris.org/tenax.html
  6. Jepson Manual - http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?Iris+tenax
  7. Burke Museum - http://biology.burke.washington.edu/herbarium/imagecollection.php?Genus=Iris&Species=tenax\
  8. Lady Bird Johnson Wildflower Center - http://www.wildflower2.org/NPIN/Plants/Conditions_Detail.asp?Symbol=IRTE
  9. Permaculture Information Web - http://permaculture.info/cgi-bin/eden?plant=3440

Data compiled by

Kelly Sutton 4/25/2006