Campanula petiolata
Campanula petiolata is a flowering plant that is called western harebell when it is distinguished from Campanula rotundifolia or simply harebell when it is considered the same species. It is in the bellflower family. This herbaceous perennial is found in areas of western North America with continental climates. It produces violet-blue, bell-shaped flowers in late summer and autumn. It is closely related to Campanula rotundifolia and is considered either a subspecies or the same species by many botanists.
Description
Campanula petiolata is a slender, prostrate to erect herbaceous perennial 10–50 centimeters tall when fully developed. The leaves at the base of the plant are round to egg shaped in shape, mostly toothed, and usually disappear before the plants flower. The basal leaves are more often ovate than round.The leaves on the lower stem are slightly widened in the middle to resembling a skinny lance point with saw toothed edges. The upper leaves are reduced to being long and thin like a grass blade or just slightly lanceolate. Due to the drier habitats of North America the foliage is firmer than that of Campanula rotundifolia. The leaf surfaces are usually smooth, but are rarely slightly rough in texture with fine hairs.
The flowering stems are usually smooth, but when hairy the very small hairs cover the stem completely rather than being confined to lines on the stem. The stems tend to be more upright than Campanula rotundifolia. The inflorescence is a panicle or raceme, with 1 to many flowers borne on very slender pedicels. The flowers are a bell shape with five points from the five sepals fused together. The flower is sometimes broader than it is long. The flowers are usually a pale lavender to dawn blue in color. Plants with pale white or albino flowers may also occur, the former with a pink-lavender stigma and the later with a creamy white stigma.
When flowering is finished the plant produces a nodding capsule that contains the very minute seeds. It has short underground rhizomes.
Taxonomy
Campanula petiolata was scientifically described and named by Alphonse Pyramus de Candolle in his 1830 publication, Monographie des campanulées. It was subsequently described as a subspecies of Campanula rotundifolia as var. petiolata by Joseph Kaye Henry in 1915. Reprints of some authoritative plant identification books, such as Handbook of Northwest Flowering Plants by Gilkey and Powell, continued to list C. petiolata as a separate species as late as 1961.It is considered an accepted species by Plants of the World Online, World Flora Online, and World Plants. It also is used as a taxon to record observations on iNaturalist. In contrast the USDA Natural Resources Conservation Service PLANTS database lists it as a synonym to Campanula rotundifolia.
Regardless of the validity of Campanula petiolata as a species, modern research indicates the European and North American populations separated due to a colonization event approximately 114 thousand years before the present. North American populations are derived from and most closely related to the Campanula rotundifolia populations of Northern Europe, especially those in Sweden and Ireland.