Red valerian is one of the few perennials capable of transforming an unpromising spot— at the base of a wall , in a rock garden , on a dry slope , or in stony soil —into a cloud of carmine-pink or white flowers for months. But it is also a plant that can self-seed profusely if left unchecked, and it is often confused with common valerian , used in herbal medicine.

In this guide, you will learn how to identify red valerian (Centranthus ruber) , choose the right location , successfully plant , obtain a second wave of flowering , and above all control its vigor to enjoy it without invasion.

Red valerian: what plant are we talking about exactly?

Scientific name, common names and frequent confusion

The “ red valerian ” of gardens most often corresponds to Centranthus ruber (red valerian), a perennial widely cultivated and now largely naturalized in France. It is also called Spanish lilac or garden valerian .

Not to be confused with common valerian (Valeriana officinalis) , whose root is used as a sedative in supplements/herbal teas. The two have different uses and different safety profiles.

How to recognize red valerian (Centranthus ruber) in the garden

Reliable identification points:

• Habit : clump of upright stems, often 60 to 80 cm (sometimes more depending on soil).
• Leaves : opposite, simple, rather lanceolate , glaucous/bluish green.
• Flowers : small tubular flowers in dense corymbs/umbels , carmine pink to red, sometimes white (cultivars).
• Typical ecology : loves warm, dry, stony environments , old walls, rock gardens (plant “saxicole/thermoxerophile”).

Field tip : if you see them spontaneously emerging from a wall crack or a very dry embankment, it's often her.

Why plant red valerian? (concrete benefits)

The perennial “anti-struggle” plant for poor soils

Red valerian is valuable when:

• The soil is poor and well-drained .
• Watering is limited
• You are looking for abundant flowering without fertilization.

It is reputed to be very easy and requires little maintenance if the drainage is good.

A nectar-producing plant that is useful for biodiversity

Red valerian attracts many pollinating insects and contributes to biodiversity in the garden.

Where should I plant red valerian so that it grows beautifully (and stays stable)?

Ideal exposure: sun first

Red valerian clearly prefers full sun . It tolerates partial shade, but flowering and longevity are better in full sun, in dry conditions.

Ground: the key factor (drainage, drainage, drainage)

This is rule number 1:

• dry to normal , very well- draining soil
• Often calcareous and poor = perfect.
• Damp soil / stagnant water = risk of root rot.

Pro tip : if your soil is heavy (clay), don't "compensate" with compost. Instead, create a drainage area : gravel, coarse sand, a slight slope, planting on a mound.

The best locations (the ones that are a hit)

• Base of wall (street side, facing due south)
• Low wall / cracks (spectacular natural effect)
• Rockery
• arid embankment
• Dry massif at the bottom or middle of the massif (depending on height)

These uses are particularly suited to its tolerance to drought and its ability to colonize mineral areas.

When and how to plant red valerian (reliable method)

Planting period

Planting is typically done in the autumn , and the plant establishes itself very well in still-warm soil. It can also be planted in the spring if you manage the watering during the initial establishment phase.

Planting density (for a professional result)

Practical guideline: 4 to 6 plants/m² to obtain a flowering clump without gaps.

Steps (planting in open ground)

1. Open a hole 2 times wider than the pot, not necessarily deeper.
2. Improve drainage (if needed): a layer of gravel + soil/gravel mix.
3. Position the root ball at ground level (avoid burying the crown).
4. Water once to settle the soil, then allow to dry between waterings.
5. Use mineral mulch (gravel) rather than organic mulch in dry soil: this limits moisture at the collar and remains consistent with its ecology.

Planting at the foot of a wall: the trick that changes everything

At the foot of a wall , water sometimes drains poorly and the soil can be very dry… or, on the contrary, compacted:

• Create a drainage strip (gravel/pebbles).
• Avoid frequent watering: 2 deep waterings in the first two weeks are better than a "small glass" every day.

Care: how to keep it flowering without letting it self-seed everywhere

The real lever: cutting off the wilted flowers

Remove the faded flower heads:

• prolongs and can trigger flowering later in the season.
• greatly reduces spontaneous reseeding (seeds).

Method: cut the spent flower stems above a leaf node or at the base depending on the desired aesthetic.

Annual felling (autumn) and stump removal (spring)

• In October the stems can be cut back
• In spring , clean up the old, dry stems before replanting.

Is it invasive?

Red valerian can spread and , more importantly , self-seed easily if you let it go to seed. The good news is that self-sown seedlings are generally very easy to pull up when they are young.

Common mistake : letting all the heads go to seed “for the birds” → you end up with dozens of seedlings the following spring.

Should I water it? Fertilize it?

• In suitable (well-draining) soil, it can withstand summer drought .
• Avoid overly rich soils and excess water: in nourished and watered soil, it can become “too enterprising”.

Propagating red valerian: sowing and division (no fuss)

Sowing: ideal if you want to "naturalize" a slope

Red valerian self -seeds spontaneously; you can also sow in spring under a cold frame (common practice).

Clump division: the most reliable method

The division is easily done:

• in spring when the new shoots appear,
• or at the end of summer .

Expert tip : divide every 3–4 years if you notice a bare center, to keep a dense and flowering clump (renewal recommended).

Varieties and combinations that work (professional rendering)

Varieties/colors

We find the following forms:

• carmine rose / red (very classic),
• white (type 'Albus'/'Alba' according to the catalogues).

Recommended plant associations for dry gardens

In dry gardens, it can be combined with other ground covers and undemanding perennials, for example: aubrieta , alyssum (Lobularia) , snow-in-summer (Cerastium tomentosum) for rock gardens/slopes.

Design logic :

• Grey/silver foliage (cerastium) + carmine pink = sharp contrast,
• White flowers + dried grasses = Mediterranean style.

Red valerian and “benefits”: what can be said without being mistaken

Medicinal use: caution and clarification

Some sources mention traditional “relaxing/sedative” uses of red valerian root in folk medicine. However, the most documented reference to valerian in the health field remains valerian (root) used as a supplement, with precautions for use (drowsiness, interactions with sedatives/alcohol, etc.).

Expert opinion : For a garden site, the safest approach is to treat Centranthus ruber primarily as an ornamental plant and avoid any recommendations for consumption or self-medication. If you mention its use as a "valerian" (sleep aid), do so only to explain the confusion and refer the user to medical advice.

FAQ — Red Valerian

Is red valerian a perennial?

Yes, Centranthus ruber is a very hardy and durable perennial

What kind of exposure is best for red valerian?

Full sun ideally, especially in dry gardens; it tolerates partial shade but flowers best in full sun.

What type of soil is suitable for red valerian?

Poor , calcareous , dry, and above all , well-drained soil . Stagnant moisture promotes root problems.

When to plant red valerian?

Preferably in autumn ; also possible in spring with well-managed post-planting watering.

How can I prevent it from reseeding itself everywhere?

Cut off faded flowers before they go to seed: this is the most effective method to limit spontaneous sowing.

Red valerian and valerian for sleep: are they the same plant?

No. Valerian “for sleep” generally refers to valerian (root) in supplement form, with precautions (drowsiness, interactions with sedatives/alcohol, etc.).

Conclusion

valerian (Centranthus ruber) is a remarkably effective perennial for bringing color to challenging areas: full sun , poor , dry , and well-drained . It rewards you with a long flowering period and significant ecological value. The secret to enjoying it for years to come: good drainage and deadheading to control self-seeding.

If you want a “professional garden” look, plant it in the right place (low wall/rockery/embankment), respect 4 to 6 plants/m² , and plan a small session of pruning the inflorescences every 2–3 weeks in the middle of the season: this is the best effort/result ratio.