Spanish lilac, valeriana: sowing, planting and care

Description and Botany

Centranthus or Valeriana est une plante vivace herbacée qui fait partie depuis peu de la famille des caprifoliacées comme les chèvrefeuilles et non plus des valérianacées comme sa proche cousine, la valériane officinale (Valeriana officinalis).

Elle pousse naturellement dans les cailloux comme dans l’argile, dans les sous-bois, les prairies humides, les berges des torrents ou le long des routes, sur les talus et rocailles arides des régions montagneuses du monde entier, notamment des régions méditerranéennes du sud de l’Europe à l’Asie Mineure. Elle s’est naturalisée dans de nombreuses régions de France.

Le Genre Centranthus compte 8 espèces de vivaces, annuelles ou bisannuelles. Les quelques espèces cultivées sont des vivaces appréciées pour leur floraison.

L’espèce la plus répandue est le Centranthus ruber, la Valériane rouge, fausse valériane, plus souvent appelé Valériane des jardins ou encore Lilas d’Espagne et ses cultivars. La valériane officinale ou « Guérit-Tout » qui appartient à un genre différent, le genre valeriana, se rencontre fréquemment également dans nos jardins où on la cultive pour ses propriétés médicinales depuis l’Antiquité.

Sur une souche ligneuse, odorante, ancrée sur des rhizomes courts, la Valériane s’élève en une belle touffe arrondie, buissonnante et ramifiée, au port dressé à lâche. La plante a un aspect un rien dégingandé. Elle atteint en moyenne 60 à 80 cm de hauteur pour 50 cm de diamètre, mais peut monter jusqu’à 1 m de haut si le sol lui convient. La croissance est rapide et la plante possède une belle longévité en sol sec et pauvre.

Les racines de Centranthe dégagent un parfum caractéristique, assez peu agréable mais si attractif pour les félins que cela lui a valu le surnom « d’Herbe aux chats ».

Les tiges cylindriques, lisses, creuses, charnues mais cassantes, couvertes de pruine et ramifiées à l’extrémité, portent des petites feuilles caduques à semi-persistantes selon la clémence du climat.

Plusieurs couleurs de Valériane des jardins : Centranthus ruber ‘Albus’, Centranthus ruber, Centranthus ruber ‘Coccineus’ (photo PAP)

Les feuilles glabres et charnues sont opposées le long de tiges, simples entières ou pennatiséquées vers la base de la touffe, ovales, elliptiques à lancéolées. Elles sont composées de 3 à 10 paires de folioles dentées. Les feuilles basales sont courtement pétiolées, les supérieures sont sessiles et engainantes.

Epaisses, elles mesurent de 2 à 20 cm de long et sont de couleur vert jade, à vert bleuté ou vert-de-gris. Le feuillage de la Valériane est aromatique, bien que d’odeur assez déplaisante, il peut s’intégrer aux salades. Si ce sont les racines de valériane qui sont principalement utilisées pour leurs vertus thérapeutiques, le feuillage possède également des propriétés médicinales, antispasmodiques et sédatives.

Très florifère, la Valériane offre une profusion de fleurs légèrement odorantes du printemps à la fin de l’été.

Dès le mois de mai et jusqu’aux premiers frimas d’octobre, les fleurs minuscules étoilées, de 2 à 5 mm de long et aplaties, apparaissent au-dessus du feuillage, groupées en corymbes ramifiées ou en panicules compactes à l’extrémité des tiges charnues.

Les fleurs de la Valériane rouge prennent la forme d’entonnoir. La corolle, composée de 5 pétales, se distingue des autres valérianes car elle est munie d’un long éperon gorgé de nectar.

La floraison des valérianes décline le plus souvent toutes les nuances de roses, allant du rose carminé au lavande rosé en passant par le rouge, elles sont parfois blanches ou d’un joli blanc rosé chez la Valériane officinale.

(©Philippe Giraud-Biosphoto)

Elles dégagent un discret parfum sucré et pénétrant lorsqu’elles s’épanouissent et font d’excellentes fleurs à couper pour les bouquets estivaux.

Cette floraison très abondante et particulièrement nectarifère, attire le vol incessant des papillons, abeilles et bourdons tout au long de l’été.

Ces petites fleurs délicates cèdent la place à des petits akènes plumeux que le vent disperse ça et là, parfois même à de bien curieux endroits, il n’est pas rare d’en croiser entre les pierres d’un muret et dans les moindres recoins ensoleillés !

Rustique au-delà de -20°C, résistante à la sécheresse estivale et aux embruns, la Valériane peut être plantée partout en France. Peu exigeante sur la nature du sol, elle pousse au soleil, indifféremment en sol caillouteux ou argileux, même si sa préférence va aux sols légers, calcaires, pauvres et secs. Sa cousine, la valériane officinale préfère quant à elle, les terrains frais et humides et de préférence mi-ombragés.

Le Centranthe est une plante quasi inratable, une aubaine pour les jardins de graviers, les rocailles sèches, pour fleurir les interstices des murets de pierre sèche. C’est une vivace incontournable dans un jardin sauvage d’allure champêtre ou un jardin de curé où elle donnera du souffle à une grande rocaille, un grand massif de vivaces ou aux talus arides et ingrats bien ensoleillés.

Centranthus ruber et Valeriana officinalis sont toutes deux connues pour leur propriétés sédatives et relaxantes.

Main species and varieties

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Centranthus ruber

This is the typical species. It thrives in gravel as well as in clay. It is ideal for colonising walls and arid areas of the garden.

• Flowering time June to September
• Height at maturity 70 cm

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Centranthus ruber Albus

A lovely wild valerian with white flowers. It has an exceptional flowering duration.

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

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Valeriana officinalis

This is a plant with medicinal properties. Its flower stem can reach 1.5 m. With very good hardiness, it thrives in woodland, rockeries, and by ponds. It naturalises well in wild gardens.

• Flowering time June to August
• Height at maturity 1,20 m

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Centranthus ruber Kempenhof

It bears lovely pink flowers. It is grown everywhere, in borders, in dry banks or rockeries, in the crevices of old walls.

• Flowering time August to October
• Height at maturity 80 cm

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Centranthus ruber Coccineus

We love its rich colour! A curate's garden flower, it self-seeds naturally and requires no care.

• Flowering time June to October
• Height at maturity 80 cm

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Centranthus ruber Star Ruber Mixed - Red Valerian Seeds

A mix of red, white, and pink valerian flowers. Easy to sow in poor soils of rockeries, banks, and on old walls.

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

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Snowcloud Garden Valerian Seeds - Centranthus ruber

A variety of garden valerian with white flowers! It is a very hardy perennial to grow in borders, in dry banks or rockeries.

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

See the product sheet

Young plantation

Where to Plant Valerian or Centranthus

Hardy down to -20°C, resistant to summer drought and sea spray, Valerian adapts to all types of climates. Undemanding in terms of soil type, it is a frugal plant that thrives in difficult conditions. It grows naturally in poor, dry, and sunny soils. Although it can tolerate any well-drained soil, it prefers dry, light, stony, even calcareous and low-fertility soils. Provide it with full sun exposure or light shade: it sometimes tends to lean over in search of light.

Even though it can also grow in any soil, common valerian will thrive more in rich, cool, and moist but well-drained soil and in partial shade.

With its rustic and warm silhouette, Valerian adds charm to soft, cottage-style gardens, where it self-seeds spontaneously among trees and bushes.

With its rapid growth, garden Valerian is ideal for quickly flowering a poor bank, an unsightly old wall, or a brand new garden; it is a born coloniser!

It stands out in Mediterranean gardens, in a dry or gravel garden, in borders, on slopes, in dry rockeries, and in perennial beds scorched by the sun, always bringing a sense of lightness to summer scenes.

Common valerian will find its place by ponds, in shaded undergrowth or in a bed or cool rockery.

Melliferous to the core, valerian flowers are useful in the vegetable garden.

When to Plant Valerian

Valerian can be planted either in spring, from February to May, or in autumn, from September to November, outside of dry and frost periods.

How to Plant Valerian

In the Ground

To plant garden Valerian or Centranthus ruber, do not add compost or fertiliser at planting, just a handful of pebbles or a scoop of gravel to improve drainage, as it has a clear preference for light soils.

In contrast, when planting common valerian, there is no need to add sand; instead, add compost, as it likes rich, compact but well-drained soils that are slightly cool and moist.

For a beautiful quick effect, plant at least 7 to 9 plants per m² spaced 30 to 60 cm apart in all directions.

• Soak the buckets in a basin of water for 15 minutes before planting
• Dig a hole 2 to 3 times the volume of the root ball
• Loosen the soil well, carefully removing roots and stones
• Spread a good layer of gravel and sand at the bottom of the hole
• Place the root ball in the middle of the hole
• Fill the hole with the extracted soil, possibly mixed with river sand
• Lightly compact
• Water once a week to ensure establishment

Centranthus ruber ‘Kempenhof’

When and how to sow valerian seeds

How to sow valerian under cover

Valerian is sown from March to June. You can collect seeds from your garden from June until the frost or choose them from our collection of false valerian or centranthus seeds. Seed germination takes 21 to 30 days.

• Sow your seeds broadcast in a tray filled with potting soil
• Lightly cover the seeds with potting soil
• Lightly press down and water generously with a fine spray
• Place the seedlings in light, without direct sunlight, at a temperature of 18°C to 20°C
• Transplant the seedlings when they are about 5 cm tall into buckets
• Install the young plants in the garden at the end of May to early June when temperatures are warm enough
• Space your plants about 30 cm apart

How to sow valerian in open ground

If the plants start to develop the following spring, you will need to be patient as they will not flower until 3 years later.

• In May, in well-warmed and well-worked soil, sow your valerian seeds broadcast
• Cover them with a thin layer of potting soil
• Press down
• Water generously with a spray and keep the soil moist until germination
• Thin out by keeping only one plant every 30 to 60 cm

Maintenance, pruning and care

How to Care for Garden Valerian or False Valerian

Once well established, Garden Valerian or Red Valerian knows how to be forgotten. It is so robust that it can do without watering, unless you plant it in the height of summer, and requires almost no maintenance. In well-drained soil, Valerians have no enemies and are insensitive to diseases.

Water once a week during the first summer following planting, but do not overdo it.

No fertiliser is necessary as Garden Valerian is an undemanding plant.

The tallest Valerians may tend to flop and require staking.

Regularly remove faded flowers to encourage the renewal of flowering, and after the first flowering, cut back the withered stems by half to promote a resurgence at the end of the season.

It tends to self-seed easily in the most unexpected places if you haven’t cut all the flower spikes. Leave them to seed if you wish to benefit from spontaneous sowing.

How to Care for and Harvest Common Valerian

Common Valerian, unlike its sap sister, is more demanding: make organic fertiliser applications in spring and autumn.

Water it more regularly in summer as it prefers soil that remains cool.

Harvesting Valerian Roots

The roots of Common Valerian contain well-known active principles for their sedative and calming properties.

In autumn, using a fork, from well-established clumps, harvest its roots. They are best consumed fresh, usually in herbal tea, but their taste is very bitter.

Pruning Valerian

Cutting back is recommended after flowering as it encourages the growth of new, more elegant foliage.

At the end of winter, in February-March, using pruning shears, cut back the entire clump to 10-20 cm above the ground to promote branching.

Every 2 to 3 years, in spring or autumn, divide the clumps to rejuvenate the plants.

Multiplication

The Valerian self-seeds abundantly and spontaneously, often in unexpected places if not cut back immediately after flowering. Seeds are harvested at ripeness, if you haven’t cut all the flower stems; otherwise, choose from our valerian seeds. Dividing clumps is also easy.

By sowing

Multiplying valerian by sowing is therefore a simple operation, but you can also collect and transplant spontaneous seedlings when the seedlings have 5 or 6 leaves. Be aware that spontaneous seedlings rarely produce plants true to the parent plant; the colours are random. To successfully sow valerian seeds, read our tips above.

Learn more in our tutorial: Valerian, Lilac of Spain: how to multiply it?

By division

Clumps of Valerian are divided in March from well-established mature clumps.

• Using a fork, gently lift the stump
• Separate a few clumps with roots
• Replant immediately in well-worked soil
• Water regularly to encourage recovery

Associating valerian with the garden

With its slightly loose silhouette, the Valerian is a reliable choice for blurred gardens, countryside gardens, wild gardens, and vicarage gardens. Easy to pair, Valerian evolves freely in a garden, quickly filling empty spaces between vicarage perennial plants such as hollyhocks and foxgloves or summer-flowering shrubs like lavateras or hibiscuses.

An example of a countryside association: Centranthus ruber, Hardy geranium ‘Johnson’s Blue’, Rose ‘Iceberg’ and a pink rose like ‘Jacques Cartier’, Lychnis coronaria ‘Alba’ against a backdrop of Deutzia ‘Mont Rose’ (photo scene ©Andrew Lawson Flora Press – Biosphoto)

It is essential in a pink garden or white garden where it adds a charming and romantic touch.

In a dry naturalist garden, it can be paired with spurges, centauries, poppies, and Damascus nigellas.

Its slightly diffuse habit will benefit from being combined with more sculptural plants like bearded irises, ornamental garlic, or sea holly.

For a profusion of flowers in an impressionistic composition, surround a few clumps of valerian with easy-going perennial plants that have generous blooms, such as potentillas and hardy geraniums, which will spread in all directions and flower from May to August with no maintenance.

Another example of a more tonal association: white delphinium like ‘Galahad’, Oriental poppy like ‘Perry’s White’, Centranthus ruber ‘Albus’ and a daisy like Leucanthemum superbum ‘Becky’

With its true pink flowers, Valerian stands out in soft colour themes: focus on delicate combinations with silver-leaved plants like wormwoods, Echinops sphaerocephalus, helichrysums, dianthus, sedums, or lavenders.

In the height of summer, its soft hues will pair well with yarrow, monardas, agastaches, coreopsis, gauras, phlox, Spanish grass, and cosmos. You can also mix valerian with its white-flowered cousins to create beautiful colourful masses.

Red Centranthus or red valerian will be perfect surrounded by herbaceous peonies and planted at the base of roses, to which it will add an extra touch of grace and colour.

On a low wall, valerian will thrive alongside alyssums, bellflowers, or aubrietas.