Eupatorium perfoliatum is an herbaceous perennial that favors wet and low-lying areas. It is an ideal shrub for rain, woodland, and herb gardens. Often referred to as common boneset, feverwort, thoroughwort, and sweating-plant, this species has properties that go far beyond the ornamental. It is a notable member of the large Asteraceae or aster family, which includes daisies and sunflowers.
Its close cousins under Eupatorium may also be referred to as bonesets or snakeroots. They have a widespread distribution throughout the northern hemisphere. E. perfoliatum is native to eastern North America.
In summer, boneset is distinguished by its downy white flowerheads. These occur as dense flat-topped clusters borne on stems that can grow as tall as 6 feet (183 cm). The plant itself is quite hairy. Upper and lower leaf surfaces, along with the side and central stems, are generously covered in white fluff. Its finely toothed leaves, which occur opposite one another, lack petioles and wrap around the entire stem. The leaf pairs are usually connected at the base, appearing as continuous structures that the stem perforates through (as indicated by the species epithet, perfoliatum).
If you’d like to attract wildlife, boneset is a fantastic plant to cultivate close to your water features. Songbirds, bees, butterflies, and insects find its fragrant blooms hard to resist. It’s particularly important to several butterfly species in their native range as it serves as a food source and habitat for them. It is NABA (North American Butterfly Association) certified as an important nectar source for adult butterflies but is not considered a food source for their larvae.
Boneset Growth, Hardiness & Climate
E. perfoliatum grows as clumps in the wild. It is fairly widespread in wetlands from as far north as Quebec and as far south as Florida, where it is found along stream banks and in thickets, meadows, prairies, and woods. Though it can tolerate full sun exposure, its roots must consistently be exposed to moist soil to prevent the leaves from scorching.
Hardy to USDA zones 3-8, boneset can withstand a wide range of ambient conditions and is generally low-maintenance. It is not sensitive to soil type and can thrive even in sandy soil as long as nutrients are available. It may even grow profusely in compact clay soil, where the roots of other plants are unlikely to survive.
When the substrate is especially fertile, the stems tend to grow tall enough to flop over, requiring stakes to keep them upright. This species naturally spreads through underground rhizomatous growth and can form small colonies. It may not be the best shrub to grow alongside other ornamental plants. Moist pondside or rain garden patches, dedicated just for this species, would work best.
How to Plant Boneset
Boneset can become established in two ways: seed or vegetative propagation. Seeds should be collected once the seed heads are fully dry and split. At this point, they should begin to take wind. If propagating outdoors, seeds can be sown directly onto the ground in fall. Sow a thick layer of them as just a few are likely to germinate in uncontrolled conditions. Those planted in controlled setups should be cold stratified prior to being sown onto a sphagnum moss-based germination medium. The setup should be exposed to daylight and the temperature should be kept at 70 – 85˚F (21 – 29˚C) to increase the chances of germination. The seeds may take 2 – 3 months to germinate.
Once the seedlings are large enough to handle, they should be transplanted to a potting mix. These should not be exposed to night temperatures that dip to below 65˚F (18˚C), and their soil should be kept moist. Seedlings can take up to a year to develop into robust young plants. Once large enough, these can be outplanted into their permanent positions. Keep in mind that a single plant can cover a ground width of 3 – 4 feet (90 – 120 cm).
Vegetative propagation is more straightforward and can be done using either root divisions or softwood cuttings. For best results, divisions should be obtained in fall, just as the plant goes dormant, or in spring, when the first new shoots appear. Cuttings should be taken in late spring. Plant these directly into soil when outdoor conditions are favourable.
How to Care for Boneset
The substrate should never be allowed to dry out completely. You may fertilize boneset during its growth period, but keep in mind that this may cause the shoots to grow too quickly and flop over. Make sure to securely stake any bent shoots, especially if they are exposed to winds. You may deadhead floral shoots once they are spent to prevent the plant from self-seeding.
Though this wildflower species is generally pest, deer, and disease-resistant, regularly monitor the leaves as they may attract leaf beetles, aphids, weevils, and thrips. Manually remove these as soon as they are spotted. To encourage the plant to grow bushier, you may cut down the shoots each spring. Ensure that it receives full sun exposure to encourage flowering.
How to Winter Boneset
Boneset shoots die back as temperatures begin to drop. You may cut them down as soon as leaves or stems turn yellow. The root system is able to persist outdoors through winter, as it enters dormancy, and can withstand temperatures that dip to -25˚C (-13˚F). If winters in your area are colder, you will have to protect the root system with a layer of mulch. Once temperatures begin to rise again in spring, the roots will enter a new growth period, producing new shoots and rhizomes.
Is Boneset Invasive or Toxic?
Due to its spreading rhizomes and self-seeding nature, common boneset may grow aggressively in fertile soil and under optimal ambient conditions. It can outcompete nearby plants and may thus be considered a nuisance plant by some horticulturists. However, it is not included in any official lists of invasive plants across North America or Europe. If you would like to grow this plant alongside other ornamentals or on the edges of a pond, it may be better to restrict its spread to within pots.
E. perfoliatum is a toxic plant. Always handle the plant with gloves as it can cause contact dermatitis. All of its parts contain phytochemicals that may induce unpleasant symptoms if ingested in high amounts. Its leaves have been used to treat dengue fever, but they can also negatively stimulate the digestive system and cause diarrhoea. Pyrrolizidine alkaloids in the plant may be exploited for herbal uses, but this must be done so with caution as these can heavily damage the liver.
Is Boneset Edible? Will Animals Eat it?
Dried boneset leaves are traditionally used to make teas and tonics for the treatment of cough, constipation, and the common cold. Nonetheless, due to the species’ toxic potential, it is not considered an edible plant. Herbal remedies with boneset as the main ingredient are available on the market and are usually safe in moderation, but health officials warn against its exclusive use to treat ailments. There is no clinical evidence that may serve as a guide for its use, and contraindications have not yet been determined.
Due to its bitter taste and hairy texture, grazing animals avoid this plant. It would be an effective addition to a deer or rabbit-resistant garden!
Where to Buy Boneset & Seeds? (UK & US)
Eupatorium perfoliatum can be purchased as seeds, plug plants, or potted plants from nurseries and garden stores within its native range. Online plant portals are also likely to carry this species. Just make sure you’re looking at listings of the actual plant and not homeopathic tablets!
If this species is unavailable, possible substitutions include its close relatives, the Joe-Pye weeds (Eupatorium fistulosum or E. pupureum).
