(beauverd spirea)
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Photo of Spiraea stevenii by Jacob Frank
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Spiraea stevenii is a very common much-branched shrub, with rounded heads of white flowers and
ovate leaves, abundant in lowland forest and
muskeg ranging into subalpine meadows and thickets across Denali. Its woody stems are reddish-brown, and plants grow 30-60 cm tall (sometimes over a meter). The leaves are alternate,
ovate to blunt-
elliptic, the edges
toothed along the upper half. The
inflorescence is a
corymb—a branched cluster, the flowers are all more or less at the same height—making rounded to flat-topped clusters of white flowers. The
sepals are reddish or green, and flowers are often pink in bud. Each small flower has five white, round petals. The
sepals are fused, with five triangular lobes. Flowers have many long, slender
stamens, lending the
inflorescence a fuzzy appearance, as well as several
carpels. Fruits are aggregated
follicles.
Spiraea stevenii is easy to identify as it is the only shrub in Denali with
ovate,
crenate-margined leaves and many small white flowers.
This perennial species flowers in early summer in Denali.
Spiraea stevenii is
monoecious with bisexual flowers. The reproductive biology of
S. stevenii has not been studied. With its many clusters of white flowers, the species is most likely insect-pollinated. Its fruits are
follicles, which split along one seam to release several seeds.
Spiraea stevenii is an amphi-Beringian endemic shrub species that grows from Chukotka to northern B.C. and the western edge of Northwest Territory. In Alaska, this species ranges from the North Slope to the upper Alaska Peninsula and Kodiak Island, and eastward to northern southeast Alaska. The species occurs commonly throughout Denali, from low to mid-elevations, both north and south of the Alaska Range crest.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
This species is mostly found on moderate elevations. Its range in Denali is 122 to 1402 m, with the highest cover at 700-900 m, but it is most likely to be found at 500-700 m. This species is infrequent above 1100 m. Plants have slightly more cover on south-facing slopes. In relation to incline, it has the highest level of cover at moderately steep slopes (12-20 degrees), angles above that are similarly occupied, with almost no cover on low and flat areas.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.
Wet to moist sites.
