Thalictrum, pigamon: planting, cultivation and association

Botany

Thalictrum, also known as Pigamon, is a herbaceous perennial plant from the same family as buttercups: the Ranunculaceae. Native to cool, moist mountainous areas, it is most commonly found in temperate regions of the Northern Hemisphere, in America, Europe, and Asia, primarily in China and Japan. In the wild, it grows at altitude, in cool, shaded areas, by torrents, in forests, in meadows, and on grassy slopes.

Vigorous, Pigamon can be planted throughout France, except in very windy regions and Mediterranean climates. Most prefer regions with cool, moist summers. The apparent lightness and delicacy of Thalictrum is deceptive: it is a robust perennial with ironclad health. Perfectly hardy, Pigamon withstands frost and copes well with negative temperatures down to -15 °C, but only for a short duration.

In Greek, Thalictrum means “to green quickly”, referring to its propensity to develop abundant foliage very quickly.

More than 130 species of rhizomatous or tuberous perennials make up this genus. From immense specimens to ground-cover species, every Thalictrum finds its place in the garden. The most commonly cultivated under our latitudes are: the Thalictrum delavayi, which is the most emblematic of the Pigamons and the Thalictrum aquilegifolium, two remarkably floriferous species. Some hybrids, such as the Thalictrum ‘Elin’, are giants that can reach nearly 3 meters in height. Among the most commonly cultivated species, Thalictrum rochebrunianum is one of the most imposing. The Thalictrum actaeifolium and the Thalictrum flavum are notable for their fragrant flowers, not to mention the adorable ground covers like the Thalictrum kiushianum that does not exceed 10 cm.

Thalictrum aquilegifolium – Botanical plate

The large Thalictrum have an upright and airy habit, forming wide, vigorous clumps, more or less spreading, with a span of up to 60 cm. They are perfect for planting in the middle or back of borders in semi-shaded areas, under trees, or in prairie gardens. The smaller ones make good plants for cool rockeries.

A bit slow to establish, Pigamon needs about two years to grow and then express its full potential. However, it is worth the wait because, as the years go by, it becomes more beautiful. Once well-rooted, this rhizomatous perennial grows quickly to form dense clumps. Almost indestructible, it has a beautiful longevity.

In April, from its robust base emerge, slowly at first, very finely divided leaves and large, slender yet sturdy stems, more or less ribbed, very branched, blue-green or purplish-brown, almost black depending on the varieties.

Very quickly, as soon as the temperature warms up, it forms in just a few weeks a large, light, flowering mass made up of a cloud of small flowers.

Spectacular, the feathery flowering gives this large perennial the appearance of a giant gypsophila. From June to mid-September, flexible, very airy flower spikes, which can reach up to 2.50 m high for the Thalictrum ‘Elin’, bear large panicles or loose corymbs, highly branched, containing countless fluffy balls that open into small star-shaped flowers (1 to 3 cm). Pink, yellow, lilac, pure white, or deep violet, they seem suspended in the air, like arachnid constellations, attached to their very fine peduncles. Lacking petals, each flower has simple or semi-double sepals that surround clusters of stamens that are sometimes so prominent that they give the flowers the appearance of fluffy pom-poms reminiscent of gypsophila or mimosa.

Thalictrum delavayi Hewitt’s double

The flowers are sometimes bicoloured with white or pink sepals and contrasting purple or lilac stamens with white tips, green-touched whites, or yellows. The sepals fall more or less quickly at the beginning of flowering, leaving the clouds of star-like stamens to provide the colour. Some cultivars, such as the Thalictrum delavayi ‘Hewitt’s Double’, do not have stamens but double flowers, resembling tiny soft, velvety roses.

The flowering lasts a good month. While Thalictrum delavayi blooms from summer until the end of autumn, the Thalictrum aquilegifolium offers a spring bloom, in May-June.

Fragrance is not the main asset of Thalictrum flowers; however, some species like Thalictrum flavum and Thalictrum actaeifolium are fragrant and exude a light bergamot scent. Particularly melliferous, they attract pollinating insects.

Each pollinated flower produces a small winged fruit. When planted in favourable conditions, in heavy, cool soil, Thalictrum (notably T. aquilegifolium) tends to naturalise by self-seeding spontaneously. As soon as they are mature, the brown seeds disperse, carried by the wind.

The cloud-like inflorescences of Pigamons make lovely airy bouquets both dry and fresh: in a vase, the flowers last a good week after being cut. They are perfect for rustic and romantic bouquets, combined with roses, lilies, or umbellifers.

A lovely foliage reminiscent of that of Columbines

The foliage, of rare elegance, is as interesting as the flowering. Deciduous, it disappears in winter and only reappears late in spring, allowing Thalictrum to be associated with bulbous plants that will occupy the space early in the season. Finely cut and light, it resembles that of certain ferns like capillary, but even more that of columbines: a resemblance that has earned Thalictrum aquilegifolium the nickname “Columbine-leaved Pigamon”. Very fine in appearance and delicate, the toothed leaves, divided into rounded and flat leaflets with 3 to 5 lobes, measure from 10 to 40 cm depending on the species. As they spread, they bring a certain opulence to the plant. The foliage takes on beautiful shades of green, from lime to glaucous slightly bluish and silvery.

While it resembles Gypsophila paniculata, Thalictrum prefers the cool environments of woodland edges; it enjoys bright exposures but without direct sunlight during the hottest hours. Therefore, it should be given a place exposed to morning or evening sun, under the canopy of deciduous trees. In contrast, Thalictrum does not like too dense shadows that would limit its flowering: do not place it in competition with shrubs that could deprive it of light and offer it soil that is too dry in summer. It is better to give it a place sheltered from dry, strong winds that could dry out the foliage and flatten the tall flower spikes.

Very easy to cultivate, and low-maintenance, it does require, however, a rich organic matter soil, well-drained and free of lime to bloom well. While it tolerates a bit of all soil types (except for very poor, dry, and stony soils), its preference typically lies with woodland soil, neutral or acidic. It enjoys light soils, even heavy ones, but that remain cool and kept sufficiently moist with good mulch during the growing season. A cool soil allows it to develop vigorously.

Thalictrum aquilegifolium in woodland

The immense specimens like Thalictrum ‘Elin’ are rarely used in isolation but are planted at the back of borders, associated with other perennials with strong growth or with shrubs that will act as supports, preventing their clumps from falling over unsightly. Ground-cover species, such as Thalictrum kiushianum, are reserved for cool rockeries and flowering walls.

Thalictrum kiusianum and Pachysandra terminalis: a lovely combination for tree base

The specific name delavayi was given to Thalictrum in honour of Father Jean-Marie Delavay, a Christian missionary who, in the 19th century, collected one of the largest botanical collections in China for the National Museum of Natural History in Paris.

Main species and varieties

Popular species

Popular varieties

Our favourites

Thalictrum delavayi - Meadow-rue

It is the best known! A magnificent late-flowering species, essential for summer scenes.

• Flowering time July to September
• Height at maturity 1,70 m

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Thalictrum aquilegiifolium - Meadow-rue

Its finely cut foliage has earned it the nickname Columbine-leaved Pigamon. It bears airy and vaporous clusters, forming a spectacular lilac mist.

• Flowering time July, August
• Height at maturity 1,20 m

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Thalictrum flavum subsp. glaucum - Meadow-rue

Also known as Yellow Pigamon, for its generous flowering of pastel yellow and fragrant flowers resembling mimosa contrasting with its beautifully cut glaucous foliage.

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

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Thalictrum kiusianum - Meadow-rue

This Lilliputian Pigamon, as tall as an apple, is a very floriferous ground-covering species.

• Flowering time May to October
• Height at maturity 15 cm

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Giant Pigamons:

Thalictrum Elin - Meadow-rue

It is a giant! The most elegant of the shadow colossi.

• Flowering time July, August
• Height at maturity 2,50 m

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Thalictrum delavayi Splendide - Meadow-rue

A very beautiful selection with larger than average flowers resembling a giant gypsophila.

• Flowering time July to November
• Height at maturity 1,75 m

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Thalictrum delavayi Splendide Album - Meadow-rue

This variety is a white-flowered clone of the cultivar 'Splendide'.

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

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Thalictrum delavayi Hewitts double - Meadow-rue

An extraordinary cultivar that you must have in the garden!

• Flowering time July to October
• Height at maturity 1 m

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Thalictrum rochebrunianum - Meadow-rue

Thalictrum rochebrunianum: One of the most imposing! Once established, its stems can reach up to 2 m high. From delicate blue-green foliage emerges a cloud of lavender or white flowers.

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

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Thalictrum aquilegifolium Album - Meadow-rue

Remarkably floriferous, we love its resemblance to gypsophila!

• Flowering time July, August
• Height at maturity 1,20 m

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Thalictrum Black Stockings - Meadow-rue

Very original, this recent introduction has large, slender stems that are purplish-brown, almost black.

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

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Thalictrum actaeifolium Perfume Star - Meadow-rue

We love the vaporous clouds of mauve and white pom-poms of this fragrant Pigamon.

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

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Thalictrum delavayi Album - Meadow-rue

Very elegant with its lovely white flowers and lime green foliage!

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

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Thalictrum delavayi Splendide - Meadow-rue

We love its appearance of a giant all-pink gypsophila!

• Flowering time July to November
• Height at maturity 1,75 m

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Thalictrum Elin - Meadow-rue

This giant is the most elegant of the shadow colossi.

• Flowering time July, August
• Height at maturity 2,50 m

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Thalictrum delavayi Splendide Album - Meadow-rue

This white-flowered clone of the cultivar 'Splendide' is of infinite poetry.

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

See the product sheet

Planting and maintenance

When to plant?

Thalictrum can be planted in spring from March to May after the frosts, or in autumn from September to November, after the heat of summer.

Where to plant?

Beneath its appearance as a beautiful perennial that is very easy to grow, Thalictrum has a few requirements: it dislikes hot and drying exposures, dry and violent winds, and competition from roots.

Vigorous, Thalictrum grows almost everywhere in France, except in dry and very windy regions and in Mediterranean climates, as it fears the scorching sun. The Pigamon will withstand summer heat in temperate regions, provided the soil remains consistently moist and cool.

With excellent hardiness, it withstands frost and can tolerate temperatures below -15 °C but only for a short duration.

Thalictrum thrives in a rather shady and well-cleared spot, sheltered from strong winds: it will flourish in partial shade, out of direct sunlight, under deciduous trees that provide a beneficial coolness. It prefers an open situation, which encourages it to reach its full height. Too dense shadows would limit its flowering: do not place it in competition with bushes that would deprive it of light. It also dislikes root competition: so make sure to give it some space!

It has a formidable enemy: the wind. A too windy situation poses a threat to these tall perennials. These lofty, feathery silhouettes are graceful as long as they stand upright! They should be given a spot sheltered from dry and violent winds that could dry out the foliage and cause the clumps to flop.

While it integrates into all settings, it truly shines as a middle or background plant in borders. The tallest varieties (Thalictrum ‘Elin’, Thalictrum delavayi ‘Splendide’, Thalictrum rochebrudianum) should be planted at the back of borders, providing a vaporous relief and striking verticality. Planting them lower down will allow for full enjoyment of their flowering.

Ground-cover species like Thalictrum kiusianum, are perfect for shady rockeries and cool flower beds.

How to plant Thalictrum?

Thalictrum is slow to establish but once well established, after two years, it is very perennial. The secret to growing this vigorous perennial lies in the planting.

• The soil should be cool to moist, but well-drained (excess water in winter can be fatal), slightly acidic, and rich in organic matter. It dislikes dry and poor soils where it will never be lush. It prefers rather heavy to light soils kept sufficiently moist with good mulch during the growing season.
• It tolerates slightly clayey soils but fears overly heavy soils. Do not hesitate to mix well-rotted compost into the soil, about 5 to 10 L, at the bottom of each hole before placing the root ball.
• Keep the soil cool at the base of the Thalictrum with mulch, especially during summer: this guarantees prolonged flowering.
• Once the young plants are established, they should not be disturbed. It is only in the second year that they will begin to thicken and flower properly.
• If you love the delicately cut and lush foliage of Thalictrum, so do gastropods! As the foliage disappears in winter, it is wise to mark the location of the plants with a small stake, to monitor snails and slugs in spring that devour the young shoots. Fern manure can help combat their attacks.
• Plant 2 to 5 plants per m², spaced at least 50 cm apart. Thalictrum dislikes root competition: avoid planting too close to bushes. It is a very airy plant that remains transparent; it is better to plant in numbers for a beautiful effect in a border.
• For giant pigamons, staking is sometimes essential, especially if they are planted in isolation. Keep this in mind: it will prevent the stems from breaking at the slightest gust of wind: a strong gust and your border will look like a battlefield after the storm! Another solution to prevent its flower spikes from collapsing in the middle of the border is to plant the Pigamon with other plants and shrubs, which it can lean on.
• A living mulch made of ground covers like Pachysandra, periwinkles, or bugle will keep the base cool.
• Water regularly during the first summer to encourage rooting.

Maintenance

Once established in ideal growing conditions, Thalictrum is not demanding. Very resistant to diseases, it requires little care and proves to be a beautiful trouble-free perennial, with robust health! As long as the soil remains cool and sufficiently nourishing.

• Every winter, spread a good layer of fallen leaves; as it decomposes, this plant mulch will turn into humus.
• Fertilise each spring with compost to improve drainage in winter and facilitate root development.
• Stake large specimens that are very sensitive to wind if necessary.
• During dry and hot periods, mulch and water very regularly in the evening. It withstands summer heat, provided that watering is daily.
• Pruning is not necessary: simply remove faded flowers regularly to prolong flowering and prevent excessive self-seeding.
• At the end of autumn, cut back the deflowered stems by half.
• Avoid cutting the plant back to the ground in autumn: as its foliage does not reappear until spring, you risk forgetting it!

Possible diseases

Pigamons have only one known enemy: gastropods. Easy to care for, it does not suffer from diseases, except perhaps powdery mildew during dry spells. Watch for slug attacks at the start of the growing season!

Sowing

Dividing clumps is possible but delicate, as the risk of damaging the root is considerable. We do not recommend it, especially since Thalictrum is very easy to sow.

Indeed, sowing is the simplest method: this perennial is very easy to grow from seeds. While some varieties, such as Thalictrum delavayi ‘Hewitt’s Double’, which is sterile, as well as hybrids, do not multiply by sowing, most meadow-rues produce seeds that germinate easily. Sowing should be done in autumn with fresh seeds from the year, harvested as soon as they turn brown, before they dry out, or with seeds sold in packets.

• Sow immediately under a cold frame in a mixture of potting soil and garden soil. This cold treatment will encourage germination.
• Plant the seeds 6 mm deep.
• Allow two to three months for germination; they will sprout in spring.
• Transplant when the seedlings have hardened off well, when they reach 5 cm tall.
• Protect young plants from slugs at the time of planting.

Pairing Thalictrum

A reliable choice for light shade borders, Thalictrum is perfect for brightening up cool areas and playing with shades and gradients. With its tall, airy silhouette, delicate and light foliage, and pastel inflorescences, it transforms a simple perennial bed into a poetic mixed border. It is the ideal companion for old roses, with which it creates opulent and romantic spring and summer scenes. It embodies the charm of English cottages and blurred gardens with a pastoral or cottage feel, bringing height, exuberance, and lightness. It is a must-have in rose gardens.

Thalictrum splendide White against a backdrop of roses: a true marvel for romantic gardens

It thrives in a community, alongside vigorous perennials that will precede or take over its flowering, such as Japanese Anemones, Bleeding Hearts, Aconite, Columbines, Astrantias, Foxgloves, or even perennial Geraniums.

Whether tall or ground-covering, Thalictrum fits into all settings, and can play the dazzling role of a mid-height or background plant creating a ethereal mist or a mossy flowering carpet for cool rockeries.

It creates a happy contrast when associated with less flexible plants like Hostas or ferns and works wonderfully with heather soil shrubs like Hydrangeas with which it composes lush beds.

You can also create a beautiful combination with Lilies, Astilbes or even grasses or Uvularia grandiflora. Thalictrum, flowering in late summer and early autumn, pairs beautifully with Asters that accompany its flowering. And to keep the base of the Thalictrum fresh, consider ground covers like Sweet Woodruff, a carpet of Periwinkles or Pink Bugle.

Another example of association: Thalictrum delavayi Splendide Album with Echinacea Catharina, Aster lateriflorus Chloe, Hosta Sagae, and Adiantum aleuticum Imbricatum

Need more inspiration? Discover our advice sheet: “Thalictrum, Pigamon: 8 beautiful association ideas”.