Thoroughworts & Bonesets

Late-flowering Thoroughwort Late-flowering Thoroughwort Spotted Joe-pye-weed Blue Mistflower

What are they?

The group of plants known as thoroughworts or bonesets are members of the Composite family - or Asteraceae as it is known technically. Most were originally in the genus Eupatorium but this has now been split into a number of closely-related genera. This group is largely characterized by having relatively large, flat-topped heads of white or pink (occasionally blue-purple) flowers, each individual flower being small and petal-less - or appearing so.

Where are they found?

Most species are found in open habitats, especially old fields, rough grassy areas and edges of wetlands and other swampy ground.


As the flowers in this group are all rather similar, most species are best identified by differences in their leaves. Pay particular attention to how the leaf is attached to the main stem of the plant and whether the leaf has a petiole (stalk) or whether the leaf clasps the stem with a rather broad base. Most species flower from late July through October.

Dog-fennel      Eupatorium capillifolium

A southern species, formerly considered rare in New Jersey, but in recent years has been increasing throughout Cape May County, often in regenerating, previously disturbed ground. Flowers late September-October. The upright, tight clumps of stems with fine, hair-like leaves are distinctive; especially so when the pendulous branch tips are laden with fluffy white flower clusters.
Dog-fennel Dog-fennel Dog-fennel Dog-fennel
Flowers on pendulous,
weeping branches
Flowers close-up
Thread-like leaves

Late-flowering Thoroughwort      Eupatorium serotinum

A localised species at the north-eastern edge of its North American range. Often a plant of swampy margins, but also occurs as an adventive in old fields. Flowers mid August to late October. Rather variable in appearance but the rough-toothed leaves with long petioles should identify it.
Late-flowering Thoroughwort Late-flowering Thoroughwort Late-flowering Thoroughwort
Relatively open clusters
of flowers
Ragged-toothed leaves
on long petioles

White-bracted Thoroughwort      Eupatorium leucolepis

Common and widespread in wet soils, especially around old sand diggings and similar habitats. Flowers August-September.
White-bracted Thoroughwort White-bracted Thoroughwort White-bracted Thoroughwort
Flower bracts
Narrow, toothed leaves

White Thoroughwort      Eupatorium album

Fairly common in dry, sandy soils, especially in the north of the county. Flowers July-September.
White Thoroughwort White Thoroughwort White Thoroughwort White Thoroughwort
Flower bracts
Oval-shaped leaves

Hyssop-leaved Thoroughwort      Eupatorium hyssopifolium

Widespread and quite common throughout Cape May in dry, sandy, open areas including fields, dunes and roadsides. Flowers late July-October. The narrow leaves are distinctive among plants of this group, but could be confused with narrow-leaved plants from other groups, e.g. Sweet Everlasting. On Hyssop-leaved Thoroughwort note the pale glandular dots on the leaves.
Hyssop-leaved Thoroughwort Hyssop-leaved Thoroughwort Hyssop-leaved Thoroughwort Hyssop-leaved Thoroughwort
Close-up of flower clusters
Narrow leaves with leaf-like
bracts clustered in their axils
Close-up of leaf showing
glandular dots

Rough Boneset      Eupatorium pilosum

Quite widespread in rough grassland, such as roadsides and along powerline cuts. Flowers July to October. A roughly downy species.
Rough Boneset Rough Boneset Rough Boneset Rough Boneset
Open flower clusters
Close-up of flowers
Paired leaves are toothed
and without petioles

Round-leaved Thoroughwort      Eupatorium rotundifolium

Widespread and quite common around Cape May, especially in dry, sandy ground. Flowers July-October. A variable species with several forms, but the rounded, rather rough, leaves should identify it.
Round-leaved Boneset Round-leaved Boneset Round-leaved Boneset
Paired leaves with
broad, rounded bases
Leaves variable but always
with well rounded bases

Common Boneset      Eupatorium perfoliatum

A common species of swampy margins and damp ground. Flowers August to October. A very distinctive species due to its paired leaves which join together and form a collar around the stem - referred to as perfoliate. Often gets large and top heavy and then prone to flopping over. Much favored by many insects in late summer and fall.
Common Boneset Common Boneset Common Boneset
Close-up of flowers
Distinctive paired leaves
clasp the stem

Sweet Joe-pye-weed      Eutrochium purpureum

Found in a few wet locations on richer soil in the south of Cape May County. Flowers July to October. Stems have a slight 'bloom' to them and flowers form large, round-topped heads.
Sweet Joe-pye-weed Sweet Joe-pye-weed Sweet Joe-pye-weed Sweet Joe-pye-weed
Flowering head
Flowers close-up

Coastal-plain Joe-pye-weed      Eutrochium dubium

A scarce plant of damp hollows along woodland edge. Flowers July to October. Stems purplish towards the top, spotted lower down, leaves usually clearly three-veined at the base and flowerheads made up of much smaller numbers of flowers - typically 5-8 rather than nine or more.
Coastal-plain Joe-pye-weed Coastal-plain Joe-pye-weed Coastal-plain Joe-pye-weed
Flowers close-up

Spotted Joe-pye-weed      Eutrochium maculatum

A plant of open, wet areas, especially grassy meadows and powerline cuts. Prefers limey or chalky soils which limits its distribution in Cape May County. Flowers August to October. Stems purplish towards the top, spotted lower down.
Spotted Joe-pye-weed Spotted Joe-pye-weed Spotted Joe-pye-weed Spotted Joe-pye-weed
Flowering head
Flowers close-up

Blue Mistflower      Conoclinium coelestinum

Favors the margins of swamps and sometimes the upper edge of saltmarsh areas. Flowers August to October. The blue-violet flowers of this species are very distinctive and unlikely to be confused with any other species, though similar to the Mexican flossflowers (Ageratum) which are planted in gardens and may be found as volunteer weeds.
Blue Mistflower Blue Mistflower Blue Mistflower
Flowers in close-up
Leaves broad at base but
with distinct petioles

Shaggy Blazing Star      Liatris pilosa

A scarce and decreasing species of dry, open, grassy places. Flowers August to October.
Shaggy Blazing Star Shaggy Blazing Star Shaggy Blazing Star Shaggy Blazing Star
Close-up of flowers
Leaves with stout
white bristles

Shaggy Blazing Star
Flowers sometimes white

Climbing Hempweed      Mikania scandens

(Climbing Hempvine) Common and readily found in swamps and wet margins, especially on the edges of reedbeds where it scrambles and climbs through the reed stems. The 'Joe-pye-weed' type flowers and climbing stems make for a unique combination.
Climbing Hempweed Climbing Hempweed Climbing Hempweed
Habit in reedbed
Close-up of flowers
Leaves triangular and stems
twining on other plants

White Snakeroot      Ageratina altissima

Though the flowers resemble those of the closely-related bonesets and thoroughworts, this plant has a very different style of growth; rather than forming discreet, tight clumps of stems, it spreads and forms extensive colonies which carpet the ground. Favors richer soils in wooded areas where it prefers to grow in the shade under trees. Particularly common south of the Cape May canal, notably around Cape May Point and in woodland at Higbee Beach WMA.
White Snakeroot White Snakeroot White Snakeroot
Close-up of flowers which are
purer white than other species
in this group
Leaves coarsely toothed and