It is not an especially attractive plant, but its stiff stems make it suitable as a cut flower for fresh and dried flower arrangements. One of its identifying features is that the main stem seems to pass right through each pair of leaves on either side of it as if it were sticking out of a hole or perforation in the middle of a single leaf (giving it its species name perfoliatum). All parts of the boneset are toxic to humans. Resist the temptation to over-fertilize boneset. It will flop over in overly fertile soil (especially in a windy spot) and need staking. This clump-forming perennial spreads via underground rhizomes. So do not plant it in a flower bed that will share space with other plants. Plan on periodically pulling out stray boneset plants to prevent them from crowding out other plants. Boneset attracts butterflies and other pollinators. Deer tend to leave it alone.
Light
Boneset tolerates partial shade. But it will flower better if you give it full sun.
Soil
Tolerant of a wide range of soil conditions, boneset is best grown in sandy soil or clay-type soil. Since this plant prefers its soil to be constantly moist, give it extra water if you grow it in sandy soil. Sandy soils are like sieves; they do not hold water well.
Water
This plant prefers constant moisture. This plant can even withstand a few days of mild flooding. Monitor the soil moisture level by inserting a tip of your finger about an inch deep; the soil should feel moist. If it doesn’t, water it thoroughly. Do not let the soil of the boneset to dry out completely.
Temperature and Humidity
Its above-ground foliage will die back in the winter, but its roots can handle temperatures down to -13 degrees Fahrenheit. It thrives in moisture-filled conditions.
Fertilizer
Boneset performs best in soil with only average fertility. If you are planting it in compost-enriched garden soil, you should not need to fertilize it at all. Do not give it too much fertilizer; only use a quarter-strength and once at the beginning of the growth period in the early spring once the ground has thawed.
Types of Boneset
Closely related to boneset are two other species of Eupatorium:
Purple Joe Pye weed (Eupatorium purpureum) Spotted Joe Pye weed (Eupatorium maculatum)
Both, like boneset, are native to North America and like to grow in wet ground. But both possess greater ornamental value than boneset, for two reasons:
They are taller plants (up to 7 feet tall) and therefore appear better in the landscape.They have pink flower heads, rather than the dull white of boneset.
Pruning
Using sterilized pruning shears, you can cut back the plants once dieback occurs as the cold weather sets in. Or, you can wait until early spring and cut back nearly to the soil level. You can prune back again in the summer to encourage bushy growth and abundant blooms. Deadheading will not help this plant rebloom, but it will help control seed and plant overgrowth.
Propagating Boneset
Boneset is best propagated via sowing seeds or root division. Boneset spreads by underground rhizomes that can often crowd an area. To prevent overcrowding and keep the plant robust, divide the plant at least every three years. Divide in the fall just as the plant appears to die back or go dormant or when new shoots appear in the spring. Here’s how to propagate via division:
How to Grow Boneset From Seed
Seeds can be sown directly in the ground in the fall or the spring after being cold stratified. Cold stratification tricks the seeds into thinking winter is over and it’s time to grow. If direct sowing outside in the fall, scatter many seeds around. You’ll use more seeds to ensure germination success since it is unreliable in an uncontrolled setting. If directly sowing outside in the spring, germination success is more reliable if you cold-stratify the seeds in the refrigerator for at least four weeks. If sowing indoors, start the seeds by cooling them in a refrigerator for 4 to 6 weeks. Using your finger, press the seeds into a bed of moistened sphagnum moss or seedling mix. No need to cover the seeds. Place it in bright, indirect light and keep the temperature between 70 to 85 degrees Fahrenheit. Keep the potting mix moist throughout the process. It can take two to three months to germinate.
Potting and Repotting Boneset
Seedlings are slow growers and can take up to a year before maturing. After a year of growth as a seedling, you can repot it in a permanent location in the ground or a larger planter. Boneset spreads when it grows. It needs a large container—at least 12 to 15 inches in diameter—with drainage holes.
Overwintering
This perennial plant naturally dies back as soon as temperatures fall. Once leaves and stems turn yellow, you can cut them or keep them intact until early spring. The roots can weather temperatures down to -13 degrees Fahrenheit. Protect the root system with a three-inch layer of mulch if you live in an area where you expect a deep winter freeze.
Common Pests
Grasshoppers, flea beetles, lygus bugs, weevils, sawflies, and several species of moth caterpillars like to feed off of boneset leaves. Insect activity leaves the plant looking ragged, but it can recover from infestations. Try less invasive controls first, such as insecticidal soap and horticultural oil, to control bug activity. If those do not work, consider using pyrethrin, a natural pesticide extract derived from chrysanthemum flowers.
How to Get Boneset to Bloom
Tiny, white flowers of boneset have a pleasant, floral scent. They are arranged in fuzzy dull-white flower clusters. It blooms in late summer for about two months. It’s rare for a mature plant not to bloom. However, since this plant is slow to mature, it may not produce blooms in its first growing season. Also, it may have lackluster flower production if the plant is not getting enough water or ample sun. Ensure the plant soil is kept consistently moist and the plant receives at least four hours of sunlight. It is not necessary to deadhead this plant. Deadheading doesn’t do anything for the plant.
Common Problems With Boneset
Boneset is relatively easy to grow and rarely experiences any problems. It does particularly well in wetlands and near water. It is not prone to any usual plant diseases.
Shriveling Leaves
Boneset is susceptible to leaf scorch or shriveling leaves when it does not get enough water. While it can tolerate a short drought, ensure it gets ample water, especially during the hottest summer months.
Foliage or Stems Falling Over
Giving this plant too much fertilizer can cause leggy growth and cause this plant to fall over. Boneset does not require feeding. A compost-enriched soil works best to get this plant the nutrients it needs. If you plan to use fertilizer, dilute it, and only give it once at the beginning of the growing season as new spring growth emerges.
