Antennaria parvifolia Nutt.
Basis for Listing
Antennaria parvifolia (small-leaved pussytoes) has a wide distribution across most states in the western United States and parts of Canada. Its distribution in Minnesota is patchy and scattered and associated with several types of dry prairie and savanna habitats. Since over 98% of the prairie and savanna habitat that was present in the state before settlement has been lost (Minnesota's Remaining Native Prairie), there is a limited amount of potential habitat remaining for the species in Minnesota. In addition, the fragmented habitat remnants in which A. parvifolia occurs are susceptible to invasion by non-native species, sand and gravel quarrying, energy production ventures, and the expansion of residential developments. Antennaria parvifolia was listed as a special concern species in Minnesota in 1984.
Antennaria parvifolia is a low-growing, mat-forming perennial. As with many other species of Antennaria, the plant has a distinctive whitish- or silvery-green color due to the presence of dense white hairs on the leaves. However, unlike in most common species of Antennaria, the white pubescence of the leaves in A. parvifolia rarely erodes away except in very old leaves. Plant height is generally 2-8 cm (0.8-3.1 in.), but can be up to 15 cm (5.9 in.). Antennaria parvifolia has leaves at the base of the plant in a basal rosette (basal leaves) and leaves distributed along the flowering stem (cauline leaves). The basal leaves are mostly spoon-shaped (spatulate), have 1 vein, and a short, sharp, pointed tip. They are 8-35 mm (0.31-1.38 in.) long and 2-15 mm (0.08-0.59 in.) wide. The cauline leaves are mostly linear, 8-20 mm (0.31-0.79 in.) long, and they have a pointed tip. Note however, that there is no flat, membranous appendage (known as a flag) at the tip of any of the cauline leaves as there is in some species of Antennaria.
Antennaria parvifolia has composite flowering heads made up of many tiny flowers. Each stalk has 2-7 flowering heads clustered tightly at the top, and male and female flowers are on separate plants. Female plants have an involucre (the set of overlapping bracts that surround the base of the flower head) that is typically 7-10 mm (0.28-0.39 in.) tall, and occasionally up to 15 mm (0.59 in.) tall. The involucre on male plants is only 5.5-7.5 mm (0.22-0.30 in.) tall. The tips of the bracts (phyllaries), which make up the involucre, can be white, pink, green, red, or brown (Great Plains Flora Association 1986; Bayer 2006).
Seven species of Antennaria occur in Minnesota. Antennaria parvifolia can be distinguished from the others by the spatulate shape of its leaves and by the tendency of the rosettes to be tighter, with more angular-looking leaves, than other pussytoes except for A. microphylla (R. Dana, Minnesota DNR, pers. comm.). Antennaria microphylla has a similar leaf shape, but its leaves are smaller than those of A. parvifolia (no more than 16 mm (0.63 in.) long and 6 mm (0.24 in.) wide). Antennaria parvifolia also has shorter flowering stems than any of the other Minnesota Antennaria species; it has relatively few flowering heads per stem; and the heads are large relative to some other species (Great Plains Flora Association 1986; Bayer 2006).
Antennaria parvifolia is found in several habitat types in Minnesota. All have dry soils and are primarily open communities, allowing for lots of sunlight to reach the ground. More specifically, the species has been found in southern dry prairie, northern dry prairie, and southern dry savanna native plant communities. In Traverse and Lincoln counties, the species grows on clay loam or sandy loam soils over glacial till. Associated species include Bouteloua curtipendula var. curtipendula (side-oats grama), B. gracilis (blue grama), and Hesperostipa comata ssp. comata (needle-and-thread grass). Sites in northwestern Minnesota are associated with ancient sand dunes and beach ridges along the former shorelines of Glacial Lake Agassiz. Some of these sites have fairly intact native plant communities and some are in disturbed areas such as roadsides or gravel pits. Associated plant species in these areas are variable depending on the site. All but one of the populations in eastern Minnesota are located on sandy soils of the Anoka Sand Plain. Associates here include Hesperostipa spartea (porcupine grass), Sporobolus cryptandrus (sand dropseed), and Koeleria macrantha (junegrass). The outlier population is located in disturbed sandy soil in Chisago County.
Biology / Life History
Antennaria parvifolia has an interesting life history trait. Throughout most of its range, populations consist primarily of female plants, which reproduce without sexual recombination (apomictic reproduction). This is the case in Minnesota where most of the plants are female and produce viable seed without being fertilized by pollen. Since most Minnesota plants are female and thus provide no pollen reward (Bierzychudek 1987), and they do not produce nectar either, it is likely that few pollinators visit plants in Minnesota populations. In a small part of the species' range (mostly in Colorado and New Mexico), there are populations where both male and female plants are regularly present and they reproduce sexually. When observing and collecting Antennaria material, it is important to note if male plants are present and if so, the ratio of female to male plants. These details are helpful in confirming which species of Antennaria was observed.
Antennaria parvifolia does spread vegetatively by stolons (aboveground horizontal stems), which lends to its mat-forming growth form. However, the primary mechanism of dispersal is by seed. The seed has a pappus of whitish bristles ringing the top of the seed. As with many plants in the sunflower family, these bristles may be caught by the wind or latch onto passing animals, thereby dispersing seeds to other locales. Seed predation is primarily by Lepidopteran seed predators (Bierzychudek 1987).
Conservation / Management
At this time, little is known about the ecology of A. parvifolia in Minnesota. It apparently has low palatability to livestock and studies in other states have shown that the species increases with grazing (Matthews 1993). This has also been seen in Minnesota, where it appears that light to moderate grazing may benefit the species. In fact, A. parvifolia may not persist in the absence of grazing or other disturbance such as sand blowouts where soil moisture and nutrients allow a dense cover of competing plants to develop (R. Dana, Minnesota DNR, pers. comm.). The open habitats in which the species grows are often managed with prescribed fire, but the effects of fire on A. parvifolia are not known. Therefore, it shouldn't be assumed that fire would be beneficial to the species even though it may occur in fire-maintained habitats.
Best Time to Search
While the leaves are distinctive and may be observed throughout the growing season, the best time to positively identify A. parvifolia is when it is flowering or in early fruit, from late May through June.
Conservation Efforts in Minnesota
Several sites that support A. parvifolia are owned and managed by private conservation organizations and public land management agencies. Some, perhaps most, of these sites are actively managed in some way, though goals and objectives vary. Unfortunately, the full effects of various management activities on A. parvifolia are not being monitored.
References and Additional Information
Bayer, R. J. 2006. Antennaria Pages 388-415 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 19. Oxford University Press, New York, New York.
Bierzychudek, P. 1987. Pollinators increase the cost of sex by avoiding female flowers. Ecology 68:444-447.
Chmielewski, J. G., C. C. Chinnappa, and J. C. Semple. 1990. The genus Antennaria (Asteraceae: Inuleae) in western North America: morphometric analysis of Antennaria alborosea, A. corymbosa, A. marginata, A. microphylla, A. parvifolia, A. rosea, and A. umbrinella. Plant Systematics and Evolution 169:151-175.
Matthews, R. F. 1993. Antennaria parvifolia. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
The Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence. 1,402 pp.