Physocarpus, Physocarpus with elder-like leaves: plant, prune and maintain

Description and Botany

The genus Physocarpus belongs to the family Rosaceae, just like hawthorn or spiraea, but it is unique in forming very decorative swollen follicles after flowering. It was named Neillia, Opulaster, and Spiraea, particularly when Carl von Linné classified it in 1793. The genus, primarily native to North America, includes about ten species of bushes, one of which is native to Southeast Asia. The most cultivated is Physocarpus opulifolius, found in the northeastern quarter of the United States from Quebec to Virginia and from Michigan to Tennessee. It grows in sandy or rocky areas up to 1500 m in altitude.

The Ninebark reaches 1.50 m to 3 m in all directions in the wild, with a bushy, well-branched habit, tending to sucker. The initially upright branches arch with age, giving a graceful, very natural appearance to the bush.

The typical species has trilobed and serratifoliate leaves that resemble those of the viburnum, with a bright yellow-green hue. They are deciduous, alternate, with well-marked veins, measuring between 5 and 8 cm long. Other species have more dissected leaves, such as monogynus, deeply lobed, sticky and villous in capitatus. The cultivars of P. opulifolius are distinguished by the beauty of their foliage colours, which can change, for example, from almost fluorescent golden yellow in spring to lime green, then to coppery yellow in autumn in ‘Dart’s Gold’, or from purple-red to dark purple appearing almost black in summer before igniting in orange and coppery pink in autumn in ‘Diabolo’.

Stunning flowering of Physocarpus ‘Diable d’Or’ (PAP).

The bark is remarkable, exfoliating in several thick layers of beige, ochre to reddish-brown, similar to eucalyptus, which has earned it the Canadian name “wood of seven barks”. The young shoots, slightly reddish, are striate. These adopt more vibrant hues, mahogany or bright red in the cultivars.

The flowers, measuring half a centimetre, appear between May and July in the form of rounded white corymbs tinged with pink, 4-5 cm in diameter, contrasting with the foliage. The flowering resembles that of spiraea, with its pink conical buds that unfold into five rounded petals. The yellow centre of the corolla hosts a multitude of stamen with sparkling orange anthers. They are very nectariferous.

They are followed by clusters of small shiny raspberry follicles that burst when pressed, revealing yellow seeds, which are appreciated by birds. The fruits remain part of the winter, eventually turning black.

The name Physocarpus opulifolia comes from the Greek ‘phusa’, meaning air bubble or vesicle, and ‘karpos’, meaning fruit, referring to the shape of the fruit. Its leaf resemblance to that of the viburnum has earned it the specific name “opulifolius”. Introduced to Europe around 1687, the numerous vibrant cultivars created in recent years have led to a resurgence of Ninebark in gardens.

In the language of flowers, Physocarpus symbolizes pretension, opulence, and wealth, which clearly reflects the generosity of its flowering enhanced by the profusion of its dentate foliage.

Several colours of foliage: Physocarpus ‘Midnight’, Physocarpus ‘Anny’s Gold’, Physocarpus ‘Diable d’Or’ (PAP), Physocarpus ‘Angel Gold’ (Denolf).

The main varieties of Physocarpus

Low Varieties

High Varieties

Physocarpus opulifolius Lady in Red - Ninebark

Compact bush with dense foliage and remarkable juvenile leaves, evolving from red to purple at ripeness. Young leaves appear from spring to summer on twisted brown branches, giving the plant a red and bicoloured appearance. Flowering in white corymbs from May to July, followed by small red fruits tinged with green in autumn.

• Flowering time June to August
• Height at maturity 1,50 m

See the product sheet

Physocarpus opulifolius Amber Jubilee - Ninebark

Recent introduction, a cross between 'Diabolo' and 'Dart's gold'. Dense bush with remarkable foliage evolving from bronze orange to yellow and green, then purple red in autumn.

• Flowering time June to August
• Height at maturity 1,50 m

See the product sheet

Physocarpus opulifolius Little Devil - Ninebark

Dwarf and compact form of Physocarpus 'Diabolo'. Foliage purple almost black in spring to copper orange in autumn.

• Flowering time June to August
• Height at maturity 1 m

See the product sheet

Physocarpus opulifolius All Black - Ninebark

This brand new physocarpus with osier-like leaves is a small deciduous bush with dense growth that dresses in exceptionally dark foliage, almost black until autumn when it turns orange-red. In May-June, it is adorned with pretty pinkish-white flowers. Requiring little maintenance, very hardy and remarkably colourful, it is perfect for small spaces, terrace and balcony arrangements.

• Flowering time June, July
• Height at maturity 1 m

See the product sheet

Physocarpus opulifolius Diabolo - Ninebark

Bushy and dense shrub, remarkable for its foliage so dark purple that it appears almost black then orange red in autumn. It blooms throughout spring, producing corymbs of dark red buds that open into small white flowers. It is not without charm in winter when its bark exfoliates.

• Flowering time June to August
• Height at maturity 2 m

See the product sheet

Physocarpus opulifolius Annys Gold - Ninebark

This new physocarpus is a bushy and vigorous shrub with beautiful acid green foliage margined with yellow to cream from spring to autumn. In June, it is adorned with white corymbs followed by small red fruits. Perfectly hardy and low maintenance, it will shine in a shrub border or a country hedge, preferably in partial shade.

• Flowering time June, July
• Height at maturity 1,75 m

See the product sheet

Physocarpus opulifolius Angel Gold

This new physocarpus has young copper yellow foliage turning golden yellow at ripeness, a very bright colour that it will retain until the end of the season. This upright bush also offers pretty white flowers in June, followed by small decorative light red fruits until autumn. Perfectly hardy, it tolerates sunny exposures well in most of our regions, as well as slightly dry and calcareous soils.

• Flowering time June, July
• Height at maturity 3 m

See the product sheet

Physocarpus opulifolius Diable D'Or - Ninebark

Young copper bronze shoots, turning purple in summer. White flowers grouped in balls in May-June, followed by small red fruits tinged with green in late summer-autumn. Bushy habit. Quite rapid growth.

• Flowering time June, July
• Height at maturity 2 m

See the product sheet

Physocarpus opulifolius Darts Gold - Ninebark

Decorative foliage shrub with golden yellow colour in spring, evolving from lemon yellow to copper yellow.

• Flowering time June, July
• Height at maturity 2 m

See the product sheet

Where, when, and how to plant a physocarpus

Where to plant Physocarpus?

Due to their extreme hardiness, you can plant Physocarpus anywhere in France, provided you give it a cool spot in summer and shelter it from drying winds.

Offer it a deep, humus-bearing, rich, and cool but well-drained, acid to neutral soil. It can, however, tolerate heavy and slightly calcareous soil.

This bush will thrive in partial shade or full sun depending on the climate, knowing that golden or variegated foliage may be damaged by too much sun exposure.

The bush remains decorative in winter, with its bark exfoliating in beige to reddish-brown plates. Plant it in a location that allows you to enjoy it throughout the year.

When to plant?

Physocarpus is a perfectly hardy shrub that is not afraid of late frosts, so it can be planted from November to March when it has bare roots (in the absence of leaves). However, avoid planting during frost periods. In containers, the plant can be planted at any time of the year, but ideally, it is best to avoid periods of intense heat or flowering.

How to plant?

Observe a planting distance of 1 m for low-vigor varieties and 2 m for others. Within a hedge, you can reduce the distance to 1.5 m.

1. Soak the root ball in a bucket of water to thoroughly moisten it.
2. Dig a planting hole 50 cm in all directions.
3. Add a 10 cm drainage layer (gravel, sand…) if your soil is clayey.
4. Add well-rotted manure or compost.
5. Place the plant in the planting hole.
6. Replace the soil and lightly firm it down.
7. Water.
8. Spread a layer of mulch at the base to maintain good moisture around the roots. This will also limit the growth of weeds.

The recovery is easy and quick and requires little maintenance.

For container cultivation, place a 3-4 cm drainage layer at the bottom of the pot (gravel, broken pottery, etc.). Add a mix consisting of 1/3 soil, 1/3 potting soil, and 1/3 coarse sand. Add mulch to maintain moisture (B.R.F, lin flakes, cocoa shells…)

The Physocarpus ‘All Black’ is well-suited for pot cultivation.

Maintenance and pruning of Physocarpus

Keep the soil cool by mulching during summer or plant ground cover plants at its base and water the soil deeply from time to time. In the evenings of hot days, mist the foliage.

Pruning is not essential but you can severely cut back the arching branches to aerate the clump after flowering and encourage the emergence of new flower buds in late summer. The shoots of compact varieties can be reduced by one-third after flowering, but you will not be able to enjoy the fruits.

Keeping old branches allows you to appreciate the cinnamon-coloured bark. It is possible to cut back the bush to 30 cm from the ground if you wish to make the base bushier and prevent it from spreading by producing numerous suckers at the expense of the mother plant.

Multiplication: cutting

The Physocarpus propagates easily in August using semi-lignified shoots. Sowing is possible but does not produce plants identical to the mother plant.

Fruiting of Physocarpus ‘Lady in Red’.

Propagation by Cuttings

To propagate your physocarpus, prepare a pot deep by filling it with potting soil mixed with sand, or carry out your cuttings in the ground if it is light, after aerating it with a fork, then moistening it.

1. Take a lignified shoot 10 cm long from a shoot of the year that is still green but hardened at the base.
2. Remove the leaves near the base of the cutting, and trim the others to reduce the leaf surface.
3. Insert the cuttings two-thirds of their height, ensuring they do not touch each other.
4. Gently firm the soil around to eliminate air pockets and ensure good contact between the potting soil and the cutting.
5. Place them in a humid environment in the shade, for example, by covering them with a cut transparent plastic bottle.
6. Towards the end of September, remove the bottle and place the cuttings under a frame until spring.
7. Separate the rooted cuttings in spring to plant them in individual pots until the following autumn.

Using and Combining Physocarpus in the Garden

Physocarpus forms very attractive medium-sized free hedges between 1.5 m and 2 m high. To create a rustic effect, pair it with Amelanchier, the viburnum sargentii ‘Onondaga’, with its lovely trilobed foliage that flowers just before, the winged euonymus (Euonymus alatus), hawthorn, or even the elder Sambucus nigra ‘Sérénade’, whose foliage colour also changes with the seasons…

An idea for a planting combination: Physocarpus ‘Diabolo’ (FD Richards), Centranthus ruber (Snapp3r), Allium ‘Globemaster’, a sage like the stunning Salvia nemorosa ‘Caradonna’, Penstemon barbatus ‘Coccineus’.

Medium and low vigour varieties will form charming small free hedges, alongside spireas (Spirea arguta, Spirea x billardii), viburnums (Viburnum carlesii ‘Chesapeake’, Viburnum x bodnantense), dwarf winged euonymus (Euonymus alatus ‘Compactus’) or a Neillia affinis… To accompany the changing colours of the Physocarpus, you can plant perennials at the base such as Heucheras or Heucherellas, or even a Cerastostigma plumbaginoides with its small electric blue flowers in summer and autumn.

A beautiful idea for a combination between the purple foliage of Physocarpus opulifolius ‘Diable d’Or’ and the pink inflorescences of Hydrangea arborescens ‘Invincibelle’.

Use golden-leaved cultivars such as ‘Angel Gold’ to brighten a semi-shaded bed or to contrast with the orange-purple foliage of Berberis thunbergii ‘Admiration’, the dark foliage of black elder ‘Black Lace’ or Physocarpus ‘Lady in Red’ or ‘All Black’. Purple varieties will work wonderfully to highlight the light blooms of perennials planted in front or the golden foliage of Euonymus japonicus ‘Aureovariegata’, Leycesteria formosa ‘Golden Lanterns’ or the silvery foliage of shrubby wormwoods or dwarf willows (Salix subopposita, lanata).

→ read on for more inspiration: “Physocarpus: 5 ideas for pairing it in the garden“