<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 a vapoury flowering in large, very light white panicles. Botanists recognise between one and four species in this genus. Aruncus dioicus is the main species, the others sometimes treated as its synonyms.

Aruncus mainly grows in damp woodland (and at edges) in mountainous areas of the temperate Northern Hemisphere. This explains their preference for cool, humus-bearing soils, shady positions, and their strong hardiness. Aruncus dioicus grows wild in France, mainly in the east (Alps, Vosges, Jura…) and in the Pyrenees. It can be found up to 1,800 metres altitude.

Aruncus belong to the large family Rosaceae, like roses, apple trees, strawberries, potentillas… Although they look quite different physically, Aruncus do show family likeness with Meadowsweet, Filipendula ulmaria (very divided foliage, white paniculate, feathery inflorescences), which is also in Rosaceae. Interestingly, Aruncus is called Queen of the Woods… each species its natural habitat! These plants are also close to spireas (also called “wild spirea”, “Goat’s-beard spirea”).

Aruncus dioicus: botanical illustration

In English, Aruncus is commonly called Goat’s-beard, Queen of the Woods, sometimes Aruncus, or wild spirea. As its species name indicates, Aruncus dioicus is dioecious, meaning there are male plants and female plants.

Aruncus is vigorous and robust, growing quickly. It forms an imposing, upright clump of long stems. It suits large gardens best, and needs plenty of space to develop properly. Aruncus (notably Aruncus dioicus) reach up to 2 metres tall at most. There is also a much more compact variety: Aruncus aethusifolius (up to 30 cm tall).

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

Aruncus flower in early to mid-summer, between May and July. Flowering is impressive but not very long-lasting.

The individual flowers are small, but extremely numerous, forming large paniculate inflorescences with a feathery, soft aspect. Flowering is elegant, understated, graceful. It slightly resembles that of Astilbes or Persicaria polymorpha. Panicles measure between 20 and 50 cm in length and are borne terminally, above the foliage.

Flowering is cream-white, adding much light to shady corners of the garden and creating a strong contrast with the dark-green foliage.

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

Flowers are tiny: 3 to 5 mm in diameter. They have five petals and five sepals (as with 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 will not have exactly the same form. Male inflorescences are rather erect, short and dense, composed of flowers bearing numerous stamens, giving a silky, feathery appearance. Female inflorescences are long and very fine, a little more pendulous. Their flowers bear three pistils. Male panicles may seem more spectacular, but female panicles are much more delicate and elegant. However, at point of purchase it is difficult to know whether a plant is male or female, since one must wait for flowering! Foliage and vegetative parts give no indication of plant sex.

Flowering of a female Aruncus plant and of a male plant

Flowers are melliferous, containing nectar and attracting pollinating insects that transfer pollen from one flower to another.

Aruncus panicles are valuable for bouquets. They add volume and set off other flowers such as roses or lilies.

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

Aruncus also impress with their abundant foliage, lush in appearance. Leaves are beautifully divided, cut, slightly reminiscent of fern fronds. They are elegant, graphic, light. 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 leaflets, dentate, ovate to lanceolate in shape, with pronounced veins. They have a light, airy aspect, leaflets not “stuck” together but spaced on fine, delicate axes. Each leaf comprises at least 20 leaflets.

Foliage is dark green, which makes the white flowering stand out, and provides an excellent backdrop for other colourful blooms when Aruncus is planted at back of borders. Foliage turns nice bronze–orange in autumn before disappearing. Indeed, this plant has deciduous foliage.

Aruncus produce small follicles (dry fruits) that open when ripe to release brown seeds, toxic to humans but appreciated by birds. As Aruncus are dioecious, only female plants will set seed. They tend to self-sow freely 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. Tall and imposing, majestic, so allow plenty of space. Its flowers, gathered in airy, light 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 sturdier than Aruncus dioicus, 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 species Aruncus dioicus. In summer it produces superb white panicles, very fine and striking, borne on dark red stems. Its foliage develops lovely autumn colours.

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

See the product sheet

Aruncus aethusifolius - Dwarf Goat's Beard

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

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

See the product sheet

Aruncus dioïcus Kneiffii - Goat's Beard

A fairly compact variety, prized for its very finely divided foliage in narrow segments. It also bears plume-like inflorescences, cream-coloured.

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

See the product sheet

Planting

Where to plant?

Ideally plant Aruncus in partial shade, although it also tolerates full sun and full shade. It is a good understorey plant, pairing nicely with ferns and hostas. If planted in sun, it will need watering much more frequently. Adapt exposure to your location: plant in shade if you live in the south of France, and in sun or partial shade in the north.

Aruncus likes cool, even moist soils, and will be happy at pond edge or near a stream. Use it to create a very natural scene. A substrate such as “woodland soil”, as found in forests, is ideal: fertile, humus-bearing, loose 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 sheltered from 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 spreads and grows quickly, forming large clumps. Allow plenty of space around it. Avoid planting in a confined spot, crowded between other plants, where it would have no room to develop.

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

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

When to plant?

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

How to plant?

1. Begin by placing root ball in a basin filled with water
2. While it rehydrates, dig a planting hole about twice size of root ball. Add compost if desired.
3. Remove Aruncus from its pot and place it in planting hole.
4. Replace soil around and firm 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 drying out too much. We strongly recommend applying a layer of mulch.

Care

Aruncus is the perfect plant for natural-style gardens, as it requires very little maintenance. It is a perennial that can easily be “forgotten” — it persists even without intervention. Its cultivation is quite similar to that of Astilbes, which also enjoy cool, semi-shaded conditions, are hardy plants and do not demand much care. You can, in fact, plant them together in the garden!

Soil should preferably remain cool, especially while plant is still young. You can provide some watering in summer, particularly during planting year. Once well established, Aruncus tolerates periods of drought.

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

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

You can remove the inflorescences once they have faded. Unlike other plants, this does not extend flowering, but helps keep a bed tidy and attractive. However, you can also leave inflorescences on female plants so they produce seeds and self-seed.

We also recommend cutting Aruncus back in late autumn, reducing the plant to ground level. However avoid doing this too early as its foliage develops beautiful autumn colours; it would be a shame not to enjoy them.

You can harvest the panicles to 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 diluted black soap in water. Beware also of sawfly larvae. Larvae of these hymenopterans strongly resemble small caterpillars, but are not. They nibble the foliage, usually leaving only the veins. Remove affected parts of the plant, search for the larvae and, if possible, remove them by hand.

Sawfly larvae eating the foliage of an Aruncus (photo Line Sabroe)

Multiplication: sowing, division

Sowing

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

1. Prepare a pot by filling it with a light potting compost, then firm and level surface.
2. Spread seeds over surface.
3. Cover with a very fine layer of substrate.
4. Water with a fine spray.
5. Place pot under cold frame.

When seedlings have reached a size suitable for handling, you can pot them on into individual pots. Plant out when they reach at least 15–20 cm in height, avoiding frosty periods (preferably plant between May and September–October).

Dividing clumps

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

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

Companion planting in the garden

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

Aruncus work well in naturalistic gardens, for example with large ornamental grasses. Create a wild-style planting, with plants of very free habit, light flowering and large, well-developed foliage. Enjoy Brunnera, Solomon’s seal, ferns… Not forgetting delicate columbine flowers! Also consider Polemonium, which offers lovely soft-blue flowers and superbly divided foliage.

As they prefer soils that remain cool, Aruncus are perfect on pond edges to create a fresh, lush 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 planting combinations to create 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 as a specimen to really show it off.

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

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

You can also use Aruncus to create a sober “white” border, achieving a very elegant, timeless garden with only white flowers and green foliage. Plant alongside gypsophila, Saxifraga stolonifera ‘Cuscutiformis’, roses with pure white flowers, lilies, Aegopodium podagraria, Dicentra spectabilis ‘Alba’…

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