Rose family (Rosaceae)
This herbaceous perennial plant forms a rosette of spreading to
ascending basal leaves. The basal leaves are up to 12" long and 4"
across, although they are usually less than two-thirds of the maximum
size; they are simple-pinnate with 5-11 pairs of sessile opposite
leaflets and a sessile terminal leaflet. The petioles of basal leaves
are relatively stout and more or less long-hairy, especially toward
their bases; they are light green, whitish yellow, or red. The leaflets
become gradually larger toward the tips of the compound leaves; they
are up to 2" long and ¾" across. The leaflets are elliptic-oblong or
oblanceolate-oblong in shape and coarsely serrated along their margins;
the teeth of the margins have narrow bristly tips. The upper leaflet
surface is yellowish green to dark green, glabrous to sparsely hairy,
and more or less shiny. The lower leaflet surface is white-canescent
from dense minute hairs, and some longer white hairs may
be present. Interspersed between these leaflets, there are often
much smaller secondary leaflets with similar characteristics.
rachises of the compound leaves are similar to their petioles,
except there are grooved above and tend to be less hairy. From the
center of the rosette of basal leaves, one or more widely spreading
stolons are produced that are 1-3' long. At intervals along these
stolons, there are leafy-bracted nodes about 4-6" apart. The stolons
are red, terete, and glabrous to sparsely long-hairy. The leafy bracts
of the nodes are simple-pinnate; they resemble the basal leaves, except
they are much smaller in size (up to 4" long and 1" across). When the
nodes have contact with moist ground, they are able to develop new
roots, from which new rosettes of basal leaves can develop. Solitary
flowers are produced from the nodes of the stolons on long naked
pedicels (floral stalks) about 2-6" long. These ascending to erect
pedicels are light green to red, terete, and nearly glabrous to
long-hairy. Each flower spans about ¾" across, consisting of 5
spreading yellow petals, 5 light green sepals, a ring of 20-25 yellow
stamens, and a central head of 20-100+ yellow pistils. The petals are
obovate or broadly elliptic in shape, while the hairy sepals are ovate,
and often cuspidate (abruptly tapering into narrow pointed tips).
Directly underneath the sepals, there are 5 floral bractlets; these
bractlets are similar to the sepals, except they are usually lanceolate
and sometimes sparingly toothed. Both the sepals and bractlets are
joined together at the base, and they are both shorter than the petals.
The blooming period occurs during the summer and early autumn for 2-3
months. Flowering is more abundant during periods of active growth.
Cross-pollination of the flowers is required for the production of
fertile seeds. The seedheads are cupped along their sides by the
persistent sepals and floral bractlets. Individual seeds are 2–2.5 mm.
long, compressed-ovoid in shape, and grooved along the upper surface.
Because the outer seed coat is somewhat corky from enclosed air
pores, the seeds are able to float on water; they can also be blown
about by the wind. The primary root system consists of a taproot
that often branches. This plant forms clonal colonies by means of
The preference is full sun, wet to mesic conditions, and calcareous
soil containing gravel or sand. This plant doesn't tolerate much
competition from taller vegetation.
Range & Habitat:
native Silverweed is uncommon in NE Illinois, while in the rest of the
state it is absent (see Distribution
Map). Silverweed has a wide distribution in boreal areas of
North America, and it also occurs in Eurasia. Habitats include sand
prairies, moist sand flats (pannes), borders of interdunal swales, low
areas along sandy ponds, small sand dunes, middle to upper beach areas,
and gravelly or sandy areas along mowed paths. In Illinois, this plant
occurs primarily along Lake Michigan. It is usually found in high
quality habitats where there is some natural disturbance from water or
wind, although it can also colonize open degraded areas that are
moist, sandy, or gravelly. This is one of the pioneer plant species
that helps to stabilize the sand in wetlands, low dunes, and beach
Faunal Associations: The flowers are usually
cross-pollinated by various bees and flies, including bumblebees,
cuckoo bees (Stelis spp.), Andrenid bees, and
Syrphid flies (Miyanishi
et al., 1991; Krombein et al., 1979; Discover Life, 2015). Both nectar
and pollen are available as floral rewards. A small number of insects
have been reported to feed on the foliage, sap, or roots of Silverweed
in North America. These species include a flea beetle (Altica
and several aphids (Chaetosiphon fragaefolii, Macrosiphum
and Rhopalosiphoninus latisiphon); see Clark et al,
(2004) and Blackman
& Eastop (2013). Foliage and flowers of Silverweed are
browsed by White-tailed Deer and other hoofed mammalian herbivores,
although they are not eaten by the granivorous American Bison. By
surviving the passage through their digestive tracts, the seeds of this
plant may be spread to new locations by these mammals.
Location: A moist gravelly area along a path and
a low area along a
sandy pond at Illinois Beach State Park in NE Illinois.
A scientific synonym of Silverweed is Potentilla anserina.
description of this plant refers to the typical subspecies, Argentina
anserina anserina. This is the only subspecies that occurs in
Other subspecies have been described that vary in such characteristics
as the hairiness of the foliage, the general size of individual plants,
the presence or absence of an upper groove on the seeds, the relative
size of the sepals versus the floral bractlets, and other
characteristics. It is relatively easy to distinguish Silverweed from
similar species (mainly Potentilla spp.). Compared
to these other
species, Silverweed can be distinguished by the greater number of
leaflets per compound leaf,
brilliant white undersides on its leaflets, sharp bristly teeth along
the margins of its leaflets, and conspicuous red stolons.