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Oregon yampah

Scientific Name:
Perideridia oregana
Native Name(s):
  1. Northern Paiute: yampah (Couture et al 1986); yapa (Couture et al. 1986); payapa (Couture et al. 1986); suiyapa (Couture et al. 1986); yapa (Fowler 1989); kazu (Fowler 1989); yapah (Fowler 1989); ya'pa' (Kelly 1932)
  2. Pit River: pEtsku (Garth 1953); paha (Kniffen 1928)
  3. Klamath: E'-pâ (Coville 1897)


Perideridia oregana emanates from tuberous roots that grow in clusters of 2 to 6. Basal blades are divided 1 to 2 times and composed of linear to oblong leaflets. Peduncles grow up to 20 cm with 6 to 10 bractlets and 10 to 29 white ray flowers. Fruits are generally oblong with thread-like ribs and are 3 to 6 mm in length. This species blooms from July to August.

Identification Tips

This species resembles Perideridia gairdneri, but Perideridia oregana is smaller and has broader and better developed bractlets.

Starch granules

Perideridia spp. storage starch granules are trimodal in size, ranging from 3-33 microns with an average size of 11 microns. Heteromorphic shape distribution; diads, triads and fours common. Many grains have central fissures, with ‘Y’ and ‘X’ markings most common. Irregular reniform grains have mesial longitudinal clefts. Cross is bright with symmetrical to wavy arms of a thin to medium thickness.


Perideridia oregana grows in open flats of slopes of pine-oak woodlands at elevations between 60 to 2100 m.


This species grows along the west coast of the United States in California, Oregon and Washington.


Yampah is an important food resource for many native populations. Digging sticks are used to harvest yampah roots in the spring, and may be consumed raw, roasted, or dried for storage over the winter months. 

As food

Northern Paiute: "From early spring well into summer root gathering was an economic activity of great importance.  Women went each day to dig ya'pa', tu˙nu'˙yu, mu'˙a', hu'˙nibui, pa˙si'go', and other roots.  These they prepared by boiling or by pit-roasting, or sometimes preserved by drying in the sun." (Kelly 1932:100-101)

Northern Paiute: "Roots of various members of the parsley family figured prominently in Paviotso diet, particularly ya'pa', commonly known as epos.  Quantities were gathered from the hills east of Surprise, and from the flats near Bear ranch in the south end of the valley.  The roots were rubbed on an open twine tray to divest them of their skins and were subsequently prepared in a variety of ways.  They might be eaten immediately, raw or boiled, or else dried in the sun and stored.  Dried ya'pa' was boiled and sometimes pounded." (Kelly 1932:101)

Northern Paiute: "Early in spring, when the snow was still on the ground, they fished in the creeks and streams.  As soon as the snow melted sufficiently, those camped in Surprise abandoned their winter quarters and crossed to the hills along the east side of the valley, stringing from Cowhead lake south to Poison spring, there to consume food buried the previous year and to dig whatever roots they could find.  All spring and well into summer they continued to wander about, gathering roots which they dried and cached for future use.  Their wanderings did not follow any set scheme; they roamed wherever the food supply seemed most promising.  A considerable range was necessary, however, for roots such as camas are essentially swamp plants, and other such as epos occur only in higher and drier country." (Kelly 1932:76)

Northern Paiute: "yapa is like a sweet potato, about as thick as the forefinger.  It is found in yellow clay and adobe in the canyons.  It is either eaten raw, boiled or roasted.  When it is roasted, it is covered with hot ashes." (Fowler 1989:43)

Northern Paiute: "yapa is dried and pounded and ground on the metate and they make a soup or mush of it by boiling.  It may be eaten raw when it is fresh.  The skin is peeled off the potato.  It is roasted in the hot sand." (Fowler 1989:43)

Pit River: "[In regards to the Hammawi] From April to June the gathering of roots was the important task…From the drying depressions on the mesa above Tulukupi, from the borders of Madeline Plains, came the paha or epos.  This was dried and stored for winter.  From the swamps came the "tule potato," knocked from the bottom with long sticks when the ice still remained; also the camass root and a variety of tulips, not to mention the tule itself.  Then from the higher lands came the berries: salmon berries, bear berries, juniper berries; with the wild plum and wild buckwheat.  All these could be dried, ground, and stored away for the winter." (Kniffen 1928:305)

Modoc: "The chief vegetable food of the Modoc seems to have been tubers and bulbs, notably camass and ipos." (Barrett 1910: 243)

Klamath: " E'-pâ.- A slender, white-flowered, umbelliferous plant, without a popular English name, but rather commonly known among the whites by its Indian designation.  This is one of the earliest spring plants gathered for food, the roots being dug about the 1st of May, at which time the contents are soft and milky.  The root is commonly dried and eaten raw." (Coville 1897:101)

Distribution Map: