Thoroughworts & Bonesets
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.
Identification
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.
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weeping branches |
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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.
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of flowers |
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.
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White Thoroughwort Eupatorium album
Fairly common in dry, sandy soils, especially in the north of the county. Flowers July-September.
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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.
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bracts clustered in their axils |
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.
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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.
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broad, rounded bases |
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.
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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.
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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.
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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.
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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.
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with distinct petioles |
Shaggy Blazing Star Liatris pilosa
A scarce and decreasing species of dry, open, grassy places. Flowers August to October.
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white bristles |
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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.
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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.
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purer white than other species in this group |
nettle-like |