Eupatorium: Planting, Growing and Care

Description and botany

The Eupatorium genus belongs to the large Asteraceae family. These tall perennials are all native to North America, with the exception of Eupatorium cannabinum, which is European.

Boneset is a hardy perennial with a bushy habit, naturally thriving in cool, even moist environments. It flourishes spontaneously in marshy meadows, ditches or woodland areas, and works wonders in our gardens when planted near a pond.

Its upright stems, often purple in colour, bear deciduous foliage in varying shades of green, turning yellow or brown in Eupatorium coelestinum and Eupatorium rugosum ‘Braunlaub’. The variety Eupatorium rugosum ‘Chocolate’ offers a delightful chocolate hue during summer before turning green when flowering begins.

Boneset foliage is typically finely lance-shaped and slightly toothed, though this spear-like form is more spread out in Eupatorium coelestinum or rugosum. The perfoliate boneset is particularly striking with its pairs of opposite, stem-piercing leaves lacking petioles. The European species stands out as an original, with E. cannabinum displaying divided leaves resembling those of Indian hemp, giving it a slightly wilder appearance than other species.

Eupatorium cannabinum – botanical illustration

Boneset flowers appear as elegant corymbs in pink, white or purple, with a light and airy appearance. Blooming begins in July, though sometimes later, but compensates with rapid, vigorous growth ensuring spectacular flowering until late summer and sometimes into October, depending on the species.

Highly nectar-rich, Eupatorium flowers attract numerous butterflies and pollinating insects, making them valuable allies near vegetable plots. This hardy perennial also works wonders in borders or large beds, either alone or combined with other moisture-loving plants. Tall species like the purple boneset, reaching 2m, are perfect for background planting. At 80cm tall, Eupatorium coelestinum is better suited to border planting in natural gardens.

Easy-going, boneset thrives in all regions provided the soil remains moist, even during the driest summers. Beyond this essential requirement for good flowering, this perennial needs no maintenance and even self-seeds. Once dried in late autumn, simply cut it back and await its return next spring!

Different boneset foliage: Eupatorium perfoliatum, Eupatorium rugosum ‘Chocolate’, Eupatorium cannabinum ‘Plenum’, Eupatorium rugosum, Eupatorium maculatum ‘Atropurpureum’.

Species and varieties

Eupatorium cannabinum Plenum

This species gets its name from its foliage resembling that of cannabis. Its burgundy-coloured stems are topped with large double flowers in corymbs. The antique pink to violet-pink colour stands out beautifully against its deep green foliage.

• Blütezeit September to November
• Höhe bei Reife 1,50 m

See the product sheet

Eupatorium coelestinum

This compact perennial offers a beautiful blue-tinged pom-pom shaped flowering from July, reaching up to 10 cm in diameter. Its deciduous foliage of very deep dark green turns chartreuse green during flowering.

• Blütezeit August to November
• Höhe bei Reife 80 cm

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Eupatorium maculatum Atropurpureum

This tall perennial stands out from its counterparts thanks to its almost black purple stems. Its large inflorescences also display a very intense purple that contrasts wonderfully with its deep green foliage.

• Blütezeit September, October
• Höhe bei Reife 2 m

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Eupatorium perfoliatum

This sturdy perennial provides an original display with its pairs of opposite leaves attached directly to the stems without petioles. Its flowering in large creamy-white corymbs emits a slight vanilla scent. Its medicinal properties are widely used in herbal medicine.

• Blütezeit September to November
• Höhe bei Reife 1,10 m

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Eupatorium rugosum Braunlaub

This tall perennial features imposing deciduous foliage that gives it a very bushy habit. Its large green leaves take on brown hues during spring, as do its white inflorescences in late summer.

• Blütezeit September, October
• Höhe bei Reife 1 m

See the product sheet

Eupatorium rugosum Chocolate

This variety gets its name from the chocolate-brown colour of its foliage, which turns green by late summer. Its flowering in soft corymbs of small white flowers is carried by stems of intense purple.

• Blütezeit October, November
• Höhe bei Reife 1,20 m

See the product sheet

Planting Eupatorium

Where to plant it?

Eupatorium is a very hardy (down to -15°C) perennial that adapts to all climates, with one condition: it needs moist, even wet soil that never dries out. In dry soil, it wilts quickly and its foliage takes on a scorched appearance. Although it prefers heavy, clay soils, it can thrive in any ordinary, moist and well-drained soil.

Apart from this requirement, eupatorium is not fussy. It doesn’t matter what the soil pH is or how polluted the air is—it settles easily in any garden. In urban areas, it’s particularly perfect for adding a wild touch and promoting biodiversity. Eupatorium is indeed very nectar-rich and will certainly attract pollinating insects, especially butterflies.

Eupatorium flowers are very nectar-rich.

For vibrant colours and beautiful flowering, choose a sunny spot if possible. However, eupatorium is naturally found at forest edges, so it doesn’t mind partial shade.

We don’t recommend growing it in pots, as this doesn’t do justice to its bushy habit and slightly wild look. Instead, eupatorium works wonderfully in borders, as a backdrop or for adding height, as well as in wildflower meadows, flower beds, or even as a standalone feature. Its preference for moist soils also makes it an ideal candidate for pond or stream edges.

When to plant eupatorium?

Eupatorium is best planted between February and April. Be cautious if you live in a mountainous climate, as young shoots may be vulnerable to late frosts. It can also be planted in autumn, between September and November, particularly in warmer climates like Mediterranean regions.

How to plant it?

• Prepare the soil by loosening it deeply with a garden fork.
• Enrich the soil by mixing in well-rotted compost.
• Dig a hole 3 times the size of the root ball.
• Place the plant, ensuring the crown (where roots meet stems) is level with the soil surface.
• Firm the soil and water thoroughly.

We recommend planting 3 to 5 plants per square metre to ensure a lush, bushy effect.

Maintenance

When grown in fresh, rich and clayey soil, the boneset requires no maintenance. In ordinary soil, a small addition of compost in early spring will encourage its regrowth.

Be aware that in dry soil, the boneset develops poorly and wilts quickly. Water regularly to maintain constant moisture at the base of your plants. Mulch to limit water evaporation and thus reduce watering. An excellent way to recycle your grass clippings, for example!

Dried clumps: Eupatorium cannabinum / Eupatorium maculatum ‘Atropurpureum’.

In any case, cut back the dried clump in late autumn to early winter. This operation helps maintain a compact shape the following spring. Cut each plant back to 10 cm from the ground when it is no longer decorative, between November and January. No need to mulch, it withstands cold temperatures down to -15°C.

Boneset is known for self-seeding very easily. A trait you can take advantage of in a wildflower meadow, but which may be problematic in flower beds. Nothing alarming though, as young plants are easily pulled out, making it simple to remove them if they become too numerous. You can also prevent self-seeding by removing faded flowers as they appear. This will also stimulate the emergence of new blooms.

In spring, watch out for slugs, which are fond of tender young shoots. If you face a gastropod invasion, treat with an organic slug control product, such as Ferramol. Otherwise, this perennial proves resistant to both diseases and pests.

Propagation: Sowing and Division

Boneset can be easily propagated by sowing or division.

Sowing Boneset Seeds

Boneset self-seeds naturally. If you wish to transplant the young seedlings, wait until they are sufficiently developed, in September-October.

You can also collect the seeds once the flowers have dried thoroughly. Store them in a dry, dark place and sow them in spring, between March and May, once the risk of frost has passed:

• Sow thinly in a seed tray using a “seed compost”.
• Place the tray in a cold frame until the seedlings reach about ten centimetres in height.
• Then transplant into individual pots.

Eupatorium maculatum seedlings.

Planting out in the ground is done in autumn, or the following spring in climates with harsh winters, particularly in mountainous areas.

Dividing Boneset

Boneset is a perennial that divides easily in early spring, between March and April. To do this:

• Dig up the clump using a sharp spade.
• Separate it into several sections, ensuring each has sufficient roots.
• Replant immediately and water.

Combining Eupatorium in the Garden

Boneset is an ideal plant for brightening the edge of a pond, a non-flooded bank or a damp ditch. Consider, for example, Eupatorium cannabinum ‘Plenum’, which has a slightly wilder appearance than its relatives. Take advantage of its rustic charm and spreading nature by planting it in a wildflower meadow, where its nectar-rich blooms will delight butterflies and other pollinators. It will work wonders on its own or alongside other moisture-loving plants like purple loosestrife or yellow loosestrife.

An example of a damp-soil planting combination: Lysimachia ephemerum, Lythrum salicaria, Eupatorium cannabinum ‘Plenum’.

Its rapid growth makes it a perfect plant for quickly creating a dense, verdant backdrop in borders. Pair the deep purple stems and flowers of Eupatorium maculatum ‘Atropurpureum’ with Echinacea purpurea ‘Magnus’. Add contrast and lightness with the soft white spikes of Veronicastrum virginicum var. album and the silky tufts of Stipa tenuifolia. To perfect this rustic look and add even more depth, tuck in a few plants of Verbena bonariensis with its airy mauve panicles.

A lovely mixed-border planting idea: Sedum ‘Autumn Joy’ (syn. ‘Herbstfreude’), Echinacea purpurea, Eupatorium maculata ‘Atropurpureum’, Perovskia ‘Blue Spire’.

The exquisite foliage colour of Eupatorium rugosum ‘Chocolate’ is also an excellent way to highlight plants with lighter foliage, such as the lime-green leaves of a hosta. It will also contrast elegantly with white blooms. Opt for tall flowers, like the graceful spikes of Cimicifuga.

Eupatorium coelestinum works wonders in a pastel-coloured border, paired with dahlias, petunias, or asters, which also appreciate moist soil.

A planting combination example: Miscanthus sinensis ‘Red Chief’, Aster ‘Pink Buttons’, Eupatorium coelestinum, Dahlia ‘Crème de Cassis’.

Finally, planting it as a standalone specimen will create a beautiful focal point in your garden. Choose among the tallest varieties, which can reach up to 2m (E. cannabinum or maculatum).

Did you know?

Eupatorium is one of the emblematic plants in Piet Oudolf’s garden, the famous landscape designer of the “Dutch Wave”. His naturalistic gardens are composed of numerous varieties of perennials and grasses, selected with unparalleled artistry to create an ever-evolving “prairie garden” scene.

In Hummelo, among the many varieties cultivated in this naturalistic paradise, the Eupatorium maculatum ‘Riesenschirm’ reaches its full height (2m) and offers a most exquisite display with its large, deep purple-pink inflorescences.

Historical anecdote

The eupatory owes its name to Mithridates VI Eupator, a king who ruled long ago in Persia, around 110 BC. The monarch, fearing poisoning and convinced of the immunity provided by his antidote, allegedly regularly consumed a preparation made from hemp agrimony (Eupatorium cannabinum). However, there is no proof that the plant in question wasn’t confused with agrimony, which bears strong formal similarities, along with numerous medicinal properties.