Description: This native perennial plant is about 2-3' long and more or less erect; it branches occasionally. The light green stems are hairless. The lower stems of individual plants are often decumbent along the ground; rootlets often develop at the nodes of these decumbent stems where the sheaths occur. The alternate leaves are up to 7" long and ¾" across, becoming smaller along the upper stems; mature leaves are spaced about ½–2" apart along each stem. They are green to dark green, oblong-lanceolate, smooth along the margins, and hairless or mostly hairless. Sometimes the leaf margins have fine hairs. The petioles of the leaves are short and slender. At the base of each petiole, there is a membranous sheath (ocrea) that wraps around the stem. This sheath often has lines of short appressed hairs, and there are short bristles along its upper rim.
Each upper stem often terminates into 1-3
narrow racemes of flowers. Each raceme is up to 6" long and more or less erect;
the flowers and their buds are distributed somewhat sparsely along its length.
Each flower is up to 1/8" across, consisting of 5 tepals, 8 stamens, and a
tripartite style. The tepals are white or pink and lack glandular dots.
Usually, only a few flowers are in bloom at the same time on a raceme. At the
base of each flower, there is a small sheath (ocreolea); this sheath has a few
short bristles (less than 1 mm. in length) along its upper rim. The blooming
period occurs from mid-summer to early fall and lasts about 1–1½
months. Each flower is replaced by a shiny black seed that is ovoid and
3-angled. The root system is fibrous and rhizomatous. Colonies of plants are
often formed.
Cultivation: Full or
partial sun, wet to moist conditions, and muddy soil are preferred. Saturated
soil containing sand or gravel is also tolerated. This plant is often found in
shallow water and it almost qualifies as an emergent-aquatic
species.
Range & Habitat: Mild
Waterpepper occurs in most counties of Illinois, where it is occasional to
locally common (see
Distribution
Map). Habitats include swamps, sunny to partially shaded seeps, edges of
ponds, and ditches. This perennial smartweed is more often found in higher
quality wetlands than many other Persicaria spp. (Smartweeds),
especially those that are weedy annuals. However, Mild Waterpepper can adapt to
disturbed wetlands as well. It displays greater tolerance of shade than some of
the other smartweeds.
Faunal
Associations: The nectar of the flowers attracts various insects,
including small bees, wasps, flies, and beetles. The caterpillars of the
butterflies Lycaena helloides (Purplish Copper) and Lycaena
hyllus (Bronze Copper) feed on Persicaria spp. (Smartweeds), as do
the caterpillars of several moths (see the
Moth Table for a listing
of these species). The seeds of smartweeds are eaten by many ducks, rails, and
granivorous songbirds (see the
Bird Table for a listing
of these species). Because the foliage of Mild Smartweed has little or no
peppery flavor, it may be eaten by mammalian herbivores to a greater extent
than the foliage of other smartweeds.
Photographic Location: A buttonbush swamp in Busey
Woods of Urbana, Illinois.
Comments:
This is one of the native species of smartweed and somewhat unusual because it
is reliably perennial. Mild Waterpepper is a member of a complex of species
that are very similar to each other. Other members of this complex include
Persicaria opelousana and Persicaria setacea, which are largely
restricted to southern Illinois. Some authorities regard these latter two
species as variants of Mild Waterpepper rather than distinct species, and there
may be some merit to this view. The species Persicaria opelousana has
flowers with greenish white tepals and its ochreoleae (small sheaths underneath
the flowers) have abundant long bristles (greater than 1 mm. in length). The
species Persicaria setacea has leaves that are conspicuously pubescent
on both their upper and lower surfaces and its ochreae (sheaths at the base of
the petioles) have long hairs and bristles. In contrast, Mild Waterpepper has
hairless leaves (or nearly so), only short appressed hairs along its ochreae,
and short bristles along the upper rim of its ochreoleae (less than 1 mm. in
length). It is also possible to confuse Mild Waterpepper with Persicaria
punctata (Dotted Smartweed) and Persicaria hydropiper (Waterpepper).
Dotted Smartweed has glandular dots on its tepals (which may be difficult to
see) and its mature leaves are more widely spaced along the stems (about
1–3½" apart). Waterpepper has ochreoleae that lack bristles and it
has more widely spaced flowers on nodding racemes. The leaves of both Dotted
Smartweed and Waterpepper have a more peppery flavor than those of Mild
Waterpepper. Another scientific name that refers to Mild Waterpepper is
Polygonum hydropiperoides.