About Pulsatilla nuttalliana (DC.) Spreng.
Pulsatilla nuttalliana (DC.) Spreng. produces flowers before its foliage develops, blooming while leaves are just starting to emerge. The stalk holding the flower may be quite fuzzy or nearly smooth, but it is never completely hairless. Below the flower head, a ring of three highly divided bracts surrounds the flowering stalk, and these bracts are very different from the plant’s leaves. Each flower grows at the end of an individual stalk, and a single plant may produce either one or many flowers. Flowers have five to eight lavender, blue-purple, or sometimes pale or nearly white sepals. Plants that bear flowers with higher numbers of sepals will typically revert to the more common six sepals in future years. Petals are oblong to elliptic in shape, and flowers face upward like bells, measuring 20–40 mm long. The center of the flower is bright yellow, with a cluster of 150–200 stamens surrounding numerous styles. The blooming period is very early; flowers often emerge as soon as snow melts, and may be covered by snow again afterward. Flowers close during cold weather and reopen when temperatures warm. After blooming, fertilized flowers develop dry fruits called achenes, each with a feathery 20–40 mm long “tail” formed by the growing style. Fertilized styles change color from whitish to pink or pink-brown, and each achene holds a single seed. The entire seed head looks like a shaggy ball of threads. The stalk continues growing after flowering, moving the seed head far above the leaves and leaving the ring of bracts much lower down. Flowers can produce seed through either cross-pollination or self-pollination, and they exhibit protogyny (female parts develop before male parts) to encourage outcrossing. Pulsatilla nuttalliana is a herbaceous perennial plant that reaches 5–40 cm in height at maturity, rarely growing as tall as 60 cm. Its stems are soft and covered in short, fine hairs. Basal leaves are ternately compound (divided into three parts), and each leaflet is further subdivided, resulting in end segments 2–4 mm wide. The terminal leaflet attaches to the leaf stalk via a very short stalk or is almost completely sessile. The full leaf has a teardrop or obovate outline, and measures 3–5 cm wide, rarely as narrow as 2.5 cm. The plant grows from a large underground tap root, and can also reproduce vegetatively by growing new rosettes from its vertically branched roots. Natural habitats for Pulsatilla nuttalliana include cool northern prairies, open slopes, fescue grasslands, forest granite outcrops, and dry open woodlands in montane and boreal regions. It also grows in human-created habitats such as clearcut areas, roadsides, and the edges of gravel pits. Pulsatilla nuttalliana is widely distributed across North America, ranging from Alaska (U.S.) and Nunavut (Canada) east to Ontario and across all western Canadian provinces. In the U.S., it grows from Idaho east to Wisconsin, and south to Utah, Colorado, and parts of New Mexico, covering all upper Midwestern states and the Northern and Southern Rocky Mountains. NatureServe lists it as globally secure, but also classifies it as a subspecies rather than a full species. It is assessed as critically imperiled in Washington, Illinois, and Ontario. Pulsatilla nuttalliana is cross-pollinated by a range of insects including honeybees, solitary mining bees in the family Andrenidae, bumblebees, and hover flies. Its seeds are dispersed by wind, or when they catch on the fur of passing animals. The plant has low forage value for herbivores because it is mildly toxic, containing protoanemonin. If grazed, it will grow new leaves from dormant buds, and populations of Pulsatilla nuttalliana increase in heavily grazed meadows. It is adapted to habitat disturbances including wildfire, but its seeds do not persist in the soil in significant quantities. Pulsatilla nuttalliana, also called prairie pasqueflower, is rarely grown as an ornamental garden plant, and is often confused with the commonly cultivated European species Pulsatilla vulgaris. It is still a useful ornamental, especially for gardeners interested in North American native species. It is planted somewhat more often in gardens designed to resemble an Upper Midwest prairie, in rock gardens, and for its value as spring forage for bees. Fresh seed of Pulsatilla nuttalliana (and other Pulsatilla species) germinates easily without stratification or other pretreatment, sprouting in about three weeks or slightly longer. Dry-stored seed that has been stored for several months requires 60 days of cool moist stratification, then sprouts at 18 to 21°C. Seeds do not store well, so they should be planted immediately or kept in cool dry conditions. Pasqueflowers can also be propagated vegetatively for gardens or habitat restoration by taking 2–4 cm root cuttings and planting them in well-drained potting medium. Seedlings are difficult to transplant, and transplanting any size of this plant requires avoiding root disturbance by digging with a large amount of surrounding soil. Good drainage is critical for the health of garden-grown prairie pasqueflower. It grows best in moist to dry soils with a neutral to slightly alkaline pH (7.0 to 8.0) and winter snow cover. It is winter hardy in USDA zones 3–5. Unlike some wildflowers, it grows well when 7 centimeters of compost is added to the topsoil. In regions with hot summers, the plant experiences less stress with partial to half-day shade. In regions with cool summers such as mountain habitats and northern prairies, it requires full sun.
