Description: This native perennial plant is 3-6'
tall and unbranched, except for flower-bearing stalks near the apex of the
plant. The central stem is stout, round, and purple-spotted or purple. It is
often covered with
fine white hairs. At
intervals along the central stem, there are whorls of 4 or 5 yellowish green
leaves. These leaves are up to 8" long and 2½" across. They are ovate to
narrowly ovate, and have serrated margins and conspicuous veins. At the apex of
the central stem, there are rather flat-headed clusters of pink or purple
flowerheads spanning several inches across. Each flowerhead is about 1/3" long,
and contains from 8-20 disk florets and no ray florets. Each disk floret has 5
tiny lobes and a conspicuous thread-like style that is pink or pale purple. The
narrow bracts at the base of each flowerhead are often pink or purple, like the
disk florets. The flowering stalks are pink or purple-spotted and often have
fine white hairs that are quite short. The blooming period usually occurs from
mid- to late summer, and lasts about a month. The flowers are often fragrant.
The florets are replaced by achenes with hair-like bristles. They are dispersed
by the wind. The root system is fibrous, and sometimes produces rhizomes. This
plant often forms small colonies.
Cultivation: The preference is full or partial sun,
and wet to moist conditions. This plant can tolerate occasional flooding if it
is temporary. The soil can contain high amounts of organic matter, or
significant amounts of gravel or sand if it is sufficiently
moist.
Range & Habitat: Spotted
Joe-Pye Weed occurs occasionally in the northern half of Illinois, and is rare
or absent elsewhere (see
Distribution
Map). Habitats include moist black soil prairies, sand prairies, sedge
meadows, marshes, fens, and swampy thickets with small trees or shrubs. It's
not often found in highly disturbed areas.
Faunal Associations: The nectar of the flowers
attracts long-tongued bees, butterflies, and skippers. The caterpillars of some
moth species feed on various parts of Eupatoriadelphus spp. (Joe-Pye
Weeds),
including Schinia trifascia (Three-Lined Flower Moth; eats flowers),
Papaipema eupatorii (Eupatorium Borer Moth; bores into stems), and
Haploa clymene (Clymene Moth; eats foliage). The seeds are a minor
source of food to the Swamp Sparrow. The foliage is apparently not a preferred
food source for mammalian herbivores, but it may be eaten occasionally by deer,
rabbits, or livestock.
Photographic
Location: A moist sandy thicket at Hooper Branch Savanna Nature
Preserve in Iroquois County, Illinois. Unfortunately, the flowers of the plant
in the upper photograph are starting to wither away.
Comments: Recently,
the Joe-Pye Weeds have been separated from the Bonesets; they have been
assigned to the genus Eupatoriadelphus, rather than Eupatorium.
Many sources of information will still refer to this species as Eupatorium
maculatum. The Joe-Pye Weeds differ from the Bonesets by their whorled leaves,
while the latter group of plants have opposite leaves. Spotted Joe-Pye Weed
differs from Eupatoriadelphus fistulosus (Hollow-Stemmed Joe-Pye Weed)
and Eupatoriadelphus purpureus (Sweet Joe-Pye Weed) by its rather
flat-headed clusters of flowers, purple-spotted or purple stems that are often
pubescent, and flowerheads consisting of 8-20 disk florets. The other species
of Joe-Pye Weed have more dome-shaped clusters of flowers, stems that are
hairless, and flowerheads consisting of 4-7 disk florets. Sweet Joe-Pye Weed is
more often found in woodlands than wetlands, while Hollow-Stemmed Joe-Pye Weed
is a wetland species that occurs primarily in the southern half of
Illinois.