Eightpetal Mountain Avens – Dryas octopetala

Alaska Wildflowers | White

White flowers of the eightpetal mountain avens in the interior of Alaska

Eightpetal Mountain Avens

Dryas octopetala

Common Names

mountain avens
eightpetal mountain avens

Synonyms

D. octopetala ssp. octopetala

Subspecies

Dryas octopetala f. argentea

Genus: Dryas
Family: Rosaceae (roses)
Order: Rosales
full classification

Duration – Growth Habit


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Perennial – forb/herb

Identification and Information

diagram of mountain avens
Britton, N.L., and A. Brown. 1913. [2]

Mountain avens display heliotropism, tracking the sun throughout the day to maximize the amount of solar radiation hitting the flower [1].

Dryas octopetala is a mat-forming perennial evergreen subshrub that grows 2.5-12 cm (1-5 inches) in height. It grows from a central root with weakly rooting horizontal branches. The leaves are leathery and oblong or ovate to elliptic 3-16 mm long and 0.5 to 6.5 mm wide. The leaf margins are dentate to serrate (differentiating the plant from the entireleaf avens D. integrifolia). The leaf sinuses (the space or indentation between the lobes in the serrated margins) range between 5-50% of the distance to the midvein (centerline). This may be one of the best distinguishing features between another species, the Alaskan mountain avens (D. alaskensis), which often has deeper sinuses, and I will discuss this further below. The top of the leaf (adaxial surface) is dark green and glabrous (hair-free), while the underside (abaxial) is often, but not always, woolly, especially along the midvein.

The peduncle is 11-125 mm (0.4-5 inches) long and supports a single flower. The flowers have sepals that are linear-oblong, 4-7 mm long, and 1.5-2.5 mm wide. Most commonly, each flower has 8 petals, hence the name octopetala, but may have as few as five or as many as 16. The petals are white or cream colored, 9-14 mm long, and 5-9 mm wide. It has numerous yellow stamens with yellow anthers and shorter greenish styles that are 16-32 mm long.

When the flower goes to seed, it develops a characteristic twist with feathery white hairs.

The twisted seed head of the mountain avens
The twisted seed head of the mountain avens

Differentiating D. octopetala from D. alaskensis

D. octopetala is very similar to another species, D. alaskensis, which is only found in Alaska and northern Canada. D. alaskensis was once considered a subspecies of D. octopetala, but in 1988 was designated as an independent species. Many sources today still list D. alaskensis as the subspecies Dryas octopetala ssp. alaskensis.

While the plants generally have some differences in characteristics, the characteristic differences are rather minor and overlapping. In the field, it may not always be possible to tell the difference between the two species.

In general, D. alaskensis may be slightly larger, with longer leaves that are more deeply serrated. The petals are very similar but may be slightly wider in the case of D. alaskensis. The sepals may be another differentiating characteristic, being larger for D. alaskensis and lanceolate to narrowly elliptic vs. linear-oblong for D. octopetala.

The only major difference I spot between the two species is leaf shape and the depth of the serrated margins – note that the images are not to scale (the Dryas alaskensis is actually larger by about 5 cm). Images were taken from the Arctos Collaborative Collection – Herbarium University of Alaska Museum of the North Database. Both samples came from the White Mountain National Recreation Area in the Alaska interior.

As I mentioned, many of the characteristics between these two species have overlapping parameters, so it may not be possible, or at least it may not be easy, to distinguish the two in the field without genetic testing (I always leave my kit at home, rats!). In the end, I don’t know how much it matters to distinguish between the two if you are not a biologist or botanist; it’s just worth noting that because of chromosomal differences, they may not readily hybridize as easily as if it was the simpler case of subspecies.

I wrote a bit about my frustration in dealing with these species in my blog post, Writing an (accurate) wildflower guide is a pain in the ….

Use in climatology and paleoecology

Dryas octopetala is used in climatology and paleoecology because its pollen is frequently found in ice cores and sediment samples. The pollen helps scientists learn more about ecology and climate during cooling and warming periods at the end of the last ice age and glacial retreat.

A major cooling event occurred while the Earth was transitioning (and warming) between the last glacial period into the present interglacial period. While the climate was shifting, starting around 14500 BP, temperatures suddenly dropped to near ice-age conditions between 12900 to 11,700 BP. This roughly 1200-year period is known as the Younger Dryas. The Younger Dryas near-glacial period is named after Dryas octopetala.

Two other shorter stadials take their name after these Dryas plants, the Older Dryas (13800 BP) and the Oldest Dryas (roughly 18000 to 15000 BP).

Dryas octopetala serves as an indicator species for the three Dryas climate events because it is susceptible to changes in temperature and moisture. During the three Dryas events, temperatures in the Northern Hemisphere shifted rapidly and dramatically, causing changes in vegetation and other environmental variables.

During the colder periods of the Dryas events, Dryas octopetala was an essential component of tundra ecosystems that developed in response to the cooling climate. The plant is adapted to cold, dry conditions and can tolerate harsh environments where other plants cannot survive. As a result, its presence in sedimentary deposits and ice cores can indicate past tundra ecosystems and the cooling events that caused them to form.

In addition to its presence in tundra ecosystems, Dryas octopetala is also sensitive to changes in moisture availability. During the warmer periods of the Dryas events, when temperatures and moisture availability increased, Dryas octopetala became less dominant in ecosystems and was replaced by other plant species better adapted to the changing conditions.

Overall, by analyzing the abundance and distribution of Dryas octopetala pollen in sedimentary deposits and ice cores from the Dryas events, researchers can reconstruct past temperature and moisture changes and gain insights into the dynamics of Earth’s climate system during these critical periods.

Uses

For information only (typically historical) – I take no responsibility for adverse effects from the use of any plant.

I found no primary sources documenting traditional food or medicinal uses of mountain avens. Plants for a Future (PFAF) cites a 1981 book by Edmund Launert Called “Edible and Medicinal Plants of Britain and Northern Europe” that the entire plant, harvested before or at flowering time, is used to make an infusion that can be used as a stomach tonic or to treat gingivitis. It also states that the leaves can be used as a tea substitute. Numerous websites make these same claims without reference (including Wikipedia) or referencing only the PFAF page. While I don’t doubt that the leaves can be used to make tea, I put very low stock in these statements regarding medicinal use.

The plant is frequently used as an ornamental plant, particularly in rock gardens or on loose ground. The roots help stabilize the (often rocky) soil beneath.

As stated above under “Information,” the plant is used extensively by scientists and ecologists to study episodes of climate change.


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Distribution and Habitat

Mountain avens have a circumpolar distribution across the entire Arctic, including Europe and Asia. In the United States and Canada, their range descends down into British Columbia, Alberta, the Pacific Northwest states, Utah, Wyoming, and Colorado.

It lives in rocky areas, alpine ridges, and alpine meadows in full sun and is typically found only in mountainous areas up to 1000 m (3200 ft.) in elevation and is most common in arctic tundra zones. It is frequently the dominant plant in areas where it is found.

Classification

RankScientific Name (Common Name)
KingdomPlantae (plantes, Planta, Vegetal, plants)
   SubkingdomViridiplantae (green plants)
      InfrakingdomStreptophyta (land plants)
         SuperdivisionEmbryophyta 
            DivisionTracheophyta (vascular plants, tracheophytes)
               SubdivisionSpermatophytina (spermatophytes, seed plants, phanérogames)
                  ClassMagnoliopsida 
                     SuperorderRosanae 
                        OrderRosales 
                           FamilyRosaceae (roses)
                              GenusDryas L. (mountain-avens)
                                 SpeciesDryas octopetala L. (eightpetal mountain-avens)
 Direct Children:
                                    FormDryas octopetala f. argentea (Blytt) Hultén

References and Further Reading

Guidebook

Field Guide to Alaskan Wildflowers, Pratt, Verna E. pg. 64

Classification and Taxonomy

Dryas octopetala L. Taxonomic Serial No.: 24619, ITIS Database

Uses

no sources

Map and Distribution

Dryas octopetala L. Published in: Sp. Pl.: 501 (1753), GBIF Database

GBIF.org (9 April 2023) GBIF Occurrence Download https://doi.org/10.15468/dl.dht4cx

Description and Information

Dryas octopetala Linnaeus Sp. Pl. 1: 501. 1753., Flora of North America

Mountain Avens (Dryas octopetala), Plant of the Week USDA and US Forest Service by Walter Fertig

Diagram, Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada, and the British Possessions. 3 vols. Charles Scribner’s Sons, New York. Vol. 2: 273. Provided by Kentucky Native Plant Society. Scanned by Omnitek Inc.

The Younger Dryas, NOAA NATIONAL CENTERS FOR ENVIRONMENTAL INFORMATION

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