<em>Aruncus</em>, goat's beard: to plant, to grow and to care for

Botany

Commonly called “Goat’s beard”, Aruncus is an imposing rhizomatous perennial with divided foliage, abundant, and airy flowering in large, very light white panicles. Botanists recognise between one and four species within this genus. Aruncus dioicus is the main one, the other species sometimes being regarded as synonyms.

Aruncus mainly grows in moist woodlands (and forest edges) of mountains in temperate regions of the Northern Hemisphere. This explains their preference for cool, humus-bearing soils, shaded situations, and their high hardiness. Aruncus dioicus grows wild in France. It is found mainly in eastern regions (Alps, Vosges, Jura…) and in the Pyrenees. It can be encountered up to 1,800 metres above sea level.

Aruncus belongs to the large Rosaceae family, like roses, apple trees, strawberries, potentillas… Although it may seem physically rather distant from these plants, Aruncus does have a family resemblance to Meadowsweet, Filipendula ulmaria (very divided foliage, white paniculate, feathery inflorescences), which also belongs to the Rosaceae. It is amusing to note that Aruncus is itself called Queen of the Woods… Each plant its natural habitat! These plants are also close to spireas (they are also called “woodland spirea”, “spirea Goat’s beard”).

Aruncus dioicus: botanical illustration

In English, Aruncus is commonly called Goat’s beard, Queen of the Woods, sometimes Aronce, or woodland spirea. As the species name indicates, Aruncus dioicus is dioecious, which means there are male plants and female plants.

Aruncus is a vigorous, robust plant that grows quickly. It forms an imposing erect clump made up of long stems. It is better suited to large gardens, and sufficient space should be allowed for it to develop correctly. Aruncus (notably Aruncus dioicus) can reach up to 2 metres in height. There is also a much more compact variety: Aruncus aethusifolius (up to 30 cm high).

Aruncus are perennials that live for a long time. They can easily remain in place for more than 15 years while requiring very little attention.

Aruncus flowers in early to mid-summer, between May and July. The display is impressive but not very long-lived.

The individual flowers are small, but very numerous and form large paniculate inflorescences with a soft, feathery appearance. Flowering is elegant, restrained, graceful. It somewhat resembles that of astilbes or Persicaria polymorpha. The panicles measure between 20 and 50 cm in length and are borne terminally above the foliage.

Flowers are cream-white, which brings a lot of light to shaded corners of the garden and creates strong contrast with the dark green foliage.

In Aruncus aethusifolius, flowers are carried on handsome dark red peduncles, which complement white spikes and green foliage very well.

Flowers are tiny: 3–5 mm in diameter. They consist of five petals and five sepals (as in many Rosaceae), and bear stamens (male flowers) or pistils (female flowers).

As its name indicates (Aruncus dioicus), Goat’s beard is dioecious: there are male plants (bearing only male flowers) and female plants (with only female flowers). Their flowering does not have exactly the same form. Male inflorescences are rather erect, short and dense, made up of flowers bearing numerous stamens, giving a silky, feathery look. Female inflorescences are long and very fine, somewhat more pendulous. Their flowers bear three pistils. Male panicles can appear more spectacular, but female panicles are much more delicate and graceful. However, when purchasing, it is difficult to know whether a plant is male or female, as one must wait for flowering! Foliage and vegetative parts give no indication of plant sex.

Flowering of a female and a male Aruncus plant

Flowers are melliferous, containing nectar that attracts pollinating insects which carry pollen from one flower to another.

Aruncus panicles are useful for arranging bouquets. They provide volume and enhance other flowers such as roses or lilies.

After flowering, inflorescences turn light brown and are much less attractive, so it is advisable to cut them off.

Aruncus also impress with abundant foliage, giving a luxuriant appearance. Leaves are beautifully divided, cut, somewhat reminiscent of fern fronds. They are elegant, graphic, airy. Leaves are very large, measuring between 20 cm and 1 m in length, borne on a long petiole. They are inserted alternately, placed one after another along the stems.

Foliage of Aruncus dioicus (photo Walter Siegmund)

Leaves are divided into many toothed leaflets, ovate or lanceolate in shape, with prominent veins. They have a light, airy aspect, the leaflets not being crowded but spaced on fine, delicate axes. Each leaf comprises at least 20 leaflets.

Foliage is dark green, providing a strong backdrop for white flowering, and makes an excellent background for other coloured blooms when Aruncus is planted at the rear of borders. Foliage develops attractive bronze–orange tones in autumn before dying back. Indeed, this plant is deciduous.

Aruncus produces small follicles (dry fruits) that open when ripe to release brown seeds, toxic to humans but eaten by birds. As Aruncus is dioecious, only female plants produce seed. They tend to self-seed spontaneously in the garden.

Main varieties of Aruncus

Most popular varieties

Our favourite varieties

Aruncus dioïcus sylvestris - Goat's Beard

This is the type species, as found in the wild. It is tall and imposing, majestic, so allow plenty of space to accommodate it. Its flowers gathered in airy, delicate panicles are much admired, as is its very finely divided foliage.

• Flowering time July to September
• Height at maturity 1,60 m

See the product sheet

Aruncus sinensis Zweiweltenkind

This variety is more compact and robust than Aruncus dioicus. It is better suited to exposed, windy sites. It offers attractive divided foliage and generous flowering in panicles.

• Flowering time August, September
• Height at maturity 1,50 m

See the product sheet

Aruncus Horatio

This variety is shorter than Aruncus dioicus. In summer it produces superb flowering in fine, striking white panicles borne on dark red stems. Its foliage develops beautiful autumn colours.

• Flowering time July, August
• Height at maturity 70 cm

See the product sheet

Aruncus aethusifolius - Dwarf Goat's Beard

This is a compact species, better suited to small gardens than Aruncus dioicus, and offering more elegant, delicate flowering. Its flowers are borne on red peduncles. It has been awarded the Award of Garden Merit by the Royal Horticultural Society (RHS).

• Flowering time June, July
• Height at maturity 30 cm

See the product sheet

Aruncus dioïcus Kneiffii - Goat's Beard

This is a fairly compact variety, valued for its very finely divided foliage with narrow segments. It also bears plume-like, creamy-white inflorescences.

• Flowering time July, August
• Height at maturity 80 cm

See the product sheet

Planting

Where to plant?

Best to plant Aruncus in partial shade, although it also tolerates full sun as well as deep shade. It is a good woodland understorey plant, pairing nicely with ferns and hostas. If planted in sun, it will need watering much more frequently. You can adapt its exposure to your location: plant in shade if you live in southern France, and in sun or partial shade in northern France.

Aruncus prefers cool, even moist soils, and will do well at pond edge or near a stream. Use it to create a very natural-looking scene. A substrate of “woodland soil”, as found in forests, is ideal: fertile, humus-bearing, friable and light. Do not hesitate to enrich soil with organic matter. Regarding pH, Aruncus prefers non-calcareous soils, rather neutral or acidic.

We also recommend planting Aruncus out of the wind, which can flatten its tall stems and panicles. Otherwise, staking may be necessary.

As Aruncus is generally quite tall, place it towards back of borders, behind lower-growing plants. It is a plant that grows vigorously and rapidly, forming large clumps. Allow plenty of space around it. Avoid siting it in a confined spot, crowded between other plants, where it would not have room to develop.

Because Aruncus is an imposing, fairly large plant and prefers substrates that remain cool, it is preferable to grow it in the ground rather than in a pot.

More compact Aruncus, such as Aruncus aethusifolius, can be placed at the front of borders or on edges. Likewise, if garden space is limited, favour smaller varieties rather than Aruncus dioicus.

When to plant?

You can plant Aruncus in spring (around April) or in autumn (September–October). The important thing is to avoid periods of intense heat or frost.

How to plant?

1. Start by placing root ball in a basin of water
2. While it rehydrates, dig a planting hole about twice size of root ball. Feel free to add compost.
3. Remove Aruncus from its pot and place it in planting hole.
4. Replace soil around and firm down to ensure good contact between soil and roots.
5. Water generously.

Continue to water regularly after planting. Be vigilant during first year to prevent soil from drying out too much. We strongly recommend applying a layer of mulch.

Care

Aruncus is perfect for natural-style gardens as it requires very little maintenance. It is a perennial that can quite easily be “forgotten” and will persist even without intervention. Its cultivation is fairly similar to Astilbes, which also prefer cool, semi-shaded conditions and are resilient plants needing little attention. You can quite happily plant them together in the garden!

It is best that soil stays cool, especially while plant is still young. You can carry out a few waterings in summer, notably during year of planting. Once well established, Aruncus tolerates periods of drought.

We recommend laying a thick layer of mulch all around the clump, made of dead leaves or BRF (ramial chipped wood). As well as keeping soil cool for longer, this will limit weed growth while enriching soil with organic matter as mulch gradually decomposes. If planted in understorey, leave tree leaves at its base or gather them around the clump, but do not remove them.

Aruncus will appreciate additions of well-rotted compost, as it likes fertile, humus-bearing substrates. Spread compost around the clump and work it lightly into soil by forking.

You can remove panicles once they have faded. Unlike other plants, this will not extend flowering but helps keep a bed looking neat and tidy. However, you can also leave panicles on female plants so they produce seeds and self-sow.

We also recommend cutting Aruncus back in late autumn, reducing plant to ground level. Avoid intervening too early, however, because its foliage turns lovely colours in autumn; it would be a shame not to enjoy them.

You can harvest panicles for use in bouquets.

Aruncus is a robust plant, rarely affected by disease. As for pests, it is sometimes attacked by black aphids, which pierce the plant and feed on its sap, weakening it. Treat by spraying black soap diluted in water. Also beware sawfly larvae. Larvae of these hymenopterans strongly resemble small caterpillars but are not. They chew foliage, usually leaving only veins. Remove affected parts of the plant, search for larvae and, if possible, remove them by hand.

Sawfly larvae devouring Aruncus leaves (photo Line Sabroe)

Propagation: sowing, division

Sowing

As Aruncus are dioecious plants, only female young plants can produce seeds. You can sow their seeds in late winter to early spring. Sowing is fairly easy; moreover, Aruncus can also self-seed.

1. Prepare a pot by filling it with a light potting compost, then firm and level the surface.
2. Scatter seeds across the surface.
3. Cover with a very thin layer of compost.
4. Water with a fine mist.
5. Place the pot under a cold frame.

When seedlings reach a size suitable for handling, pot them into individual pots. Plant out into open ground when they are at least 15-20 cm tall, avoiding frosts (preferably plant between May and September–October).

Division of clumps

Division is carried out in late winter or autumn, and it is best reserved for specimens at least five years old. This operation is not necessary to increase plant vigour or to regenerate it; Aruncus can remain in place for years without being divided. Division is somewhat delicate because the stump is woody, and the roots are more or less tap-rooted.

1. Choose an adult, well-developed specimen several years old.
2. Lift the clump, or (if extensive) at least part of it.
3. Remove excess soil to make the rootstock clearly visible.
4. Cut the rootstock into several segments using a sharp knife.
5. Prepare ground to receive the new young plants from division. Preferably choose a semi-shaded spot on fertile, moist soil.
6. Plant.
7. Water well.

Companion planting in the garden

Obviously, Aruncus are perfect for integrating into a woodland understorey. With their large white panicles, they bring brightness to shaded areas of garden! Plant them with hostas, ferns, brunneras, ligularias, foxgloves, Paris polyphylla, etc. Also discover the delicate, airy flowering of Saxifraga stolonifera ‘Cuscutiformis’! You can plant Aruncus at woodland edge to accompany transition from open area into woodland.

Aruncus integrate well into natural-style gardens, for example with large grasses. Create a wild-style garden, with plants with a very free habit, light, airy flower displays, and large, well-developed foliage. Make use of Brunnera, Solomon’s seal, ferns… Not forgetting the delicate blooms of columbines! Also consider Polemonium, which offers beautiful soft-blue flowers and superbly dissected foliage.

As they appreciate soil that stays cool, Aruncus are perfect on a pond edge, to create a cool, luxuriant atmosphere. Pair them with ferns (Matteuccia, Osmunda…), Filipendula ulmaria, Astilbes, Asian primroses… Also discover the superb flowering of Iris sibirica. You can also grow bogbean, Menyanthes trifoliata.

An idea for a planting combination for a very natural atmosphere, for example on a pond edge: Digitalis mertonensis, Aruncus ‘Horatio’ and Veronicastrum virginicum ‘Lavendelturm’ / Filipendula ulmaria (photo Algirdas) / Primula bulleyana / Aruncus dioicus

As Aruncus is an imposing plant, impressive for its foliage and flowering, you can plant it alone, as a specimen, to really showcase it.

If you want to incorporate it into a border, place Aruncus toward the back. It will set off large colourful flowers of roses, lilies, gladioli or irises, or the bright yellow inflorescences of Lysimachia. You can place lower, groundcover plants in front and around it: alchemilla, hardy geraniums, heucheras, hostas…

Use Aruncus to compose an airy bed, with other light plants that play with the wind and create a sense of movement: grasses, gypsophila, Gaura, flax, Veronicastrum, columbines, Cosmos bipinnatus… Don’t hesitate to pair Aruncus with Astilbes too, as these plants have very similar cultivation requirements and both offer light, feathery flowering displays!

You can also use Aruncus to create a ‘white’ bed, understated, producing a very elegant and timeless garden, with only white flowerings and the green of the foliage. Place alongside them gypsophilas, Saxifraga stolonifera ‘Cuscutiformis’, roses with pure white flowers, lilies, Aegopodium podagraria, Dicentra spectabilis ‘Alba’…

Aruncus integrate easily into shade gardens. Scene with Lysimachia punctata, Hosta, Aruncus, Berberis thunbergii (photo Virginie Douce) / Aruncus dioicus / Hosta ‘Fire and Ice’