Red valerian (Centranthus ruber) is a perennial shrub that is comfortable in alkaline conditions and can even be found growing from limestone mortar in castle walls. Its leaves and roots are occasionally incorporated into salads or made into soup. But these plants are red valerian and should not be confused with true valerian and has no demonstrated medicinal value.
I. Appearance and Characteristics
Valeriana rubra (synonym Centranthus ruber), the red valerian, spur valerian, kiss-me-quick, fox’s brush, devil’s beard or Jupiter’s beard, is a popular garden plant grown for its ornamental flowers.
Valeriana rubra is a perennial plant, usually as a subshrub though it can take any form from a herbaceous plant to a shrub depending on conditions; the plants are usually woody at the base. The leaves are generally 5–8 cm in length. Their form changes from the bottom to the top of the plant, the lower leaves being petiolate while the upper leaves are sessile. The leaves grow in opposite pairs and are oval or lanceolate in shape.
The plant flowers profusely, and though the individual flowers are small (no more than 2 mm), the inflorescences are large and showy. The flowers are small in rounded clusters each with 5 fused petals and a spur. The most typical color is a brick red or purplish red, but colors include deep crimson, pale pink, and lavender. Centranthus ruber ‘Albus’ (about 10% of individuals) has white blooms. Flowering takes place in early summer and, in cool summer areas, continues sporadically throughout the summer and into fall. The cultivar ‘coccineus’ is especially long-blooming. The blooms have a strong and somewhat rank scent.
They are pollinated by both bees and butterflies and the plant is noted for attracting insects. It is used as a food plant by the larvae of some Lepidoptera species including angle shades. Seeds have tufts similar to dandelions that allow wind dispersal, and as such can self-seed freely and become invasive if not properly controlled.
Valeriana rubra is native of the Mediterranean region, ranging from Portugal and Spain to France, Italy, former Yugoslavia, Albania, Greece and European Turkey, and from Morocco to Algeria and Tunisia. It has been introduced into many other parts of the world as a garden escape. It is naturalised in France, Australia, Great Britain, Ireland, Isle of Man and the United States. In the US it can be found growing wild in such western states as Arizona, Utah, California, Hawaii, Washington, and Oregon, usually in disturbed, rocky places at elevations below 200 m.
It is often seen by roadsides or in urban wasteland. It can tolerate very alkaline soil conditions. Because of its ability to tolerate alkaline conditions, Valeriana rubra can tolerate lime in mortar, and may frequently be seen growing on old walls in Italy, southern France and south-west UK.
II. How to Grow and Care
Sunlight
Spur valerian does best in a full-sun position. It can tolerate partial shade too, but it may not produce quite as impressive a bloom through the summer. The plant may flop over if it’s too shaded.
Temperature and Humidity
Spur valerian does not like overly hot and humid summers which is why it won’t grow in tropical conditions.
Watering
A drought-tolerant plant, spur valerian doesn’t need a lot of water. Young seedlings will need light watering, but established plants can cope fine with natural rainfall alone. This plant doesn’t tolerate over-watering well. The only time you’ll need to water a mature specimen is if there has been a prolonged very hot spell and the soil is excessively dry. It is even used in xeriscape gardens with restricted water.
Soil
If you’re looking for a plant that will thrive despite poor soil conditions, spur valerian would be a good choice. It copes with dry, infertile soils incredibly well and will flourish in a compact form in areas where many other plants die off.
It does prefer a slightly alkaline soil type. Limestone can be added to create better growth conditions if your soil is more on the acidic side. If the soil you’re planting in is a richer variety, you may find that the tall spur valerian will benefit from staking.
Fertilizing
As you would expect with a plant that copes well in infertile soils, you won’t need to fertilize your spur valerian.
Pruning
Spur valerian dies to the ground in the winter and bounces back with the appearance of daughter plants around each base in the spring. It self-seeds readily, and cutting it back drastically after the bloom period can help to control any unwanted spread. It also means the bloom will be more abundant the following year. Spur valerian often blooms from early summer to September, so don’t be tempted to cut back the flowers too early.
Propagation
Basal cuttings can be taken in the spring or early summer, or you can divide the roots in spring or fall to produce new plants. Division every few years is recommended as this prevents the central section of clumps from dying off, and it stops the root system from becoming overcrowded. Spur valerian can be propagated through several methods. Here’s how:
- Dig up a clump in spring or fall.
- Look for natural divisions in the root and separate them with your hands or garden shears. Each division should have its own set of roots.
- Plant each 12-24 inches apart and water.
How to Grow From Seed
Growing spur valerian from seed produces good results. If you plan to sow during the winter, pick a sheltered spot, keep the soil slightly moist, and use a tray that can be covered to protect the seeds from any hard frost.
The seedlings can be transplanted into the ground when the temperatures rise, usually around May. Spur valerian seeds germinate rapidly when temperatures climb above 68 degrees Fahrenheit.
Sowing directly into the ground in spring is also possible. As the first leaves appear, it’s a good idea to thin them out, selecting the most vigorous seedlings to keep. Make sure you water the seedlings regularly, but only enough to keep the soil mildly moist. Too much watering makes the plants look weedy.
Overwintering
These plants are quite hardy and will survive cold weather. They die back in the winter and grow from the ground up in the spring.
How to Get to Bloom
In order to produce the most impressive bloom, ensure your plant gets full sun. Spur valerian produces star-shaped flowers in vivid colors. Blooms start in late spring and early summer and last through the fall. Make sure soil is well-draining and deadhead regularly through the summer to prolong blooms.
Pests and Diseases
Spur Valerian is relatively a trouble-free plant and isn’t susceptible to significant pest or disease problems.
III. Uses and Benefits
A perfect border plant, it is a spectacular addition to beds, borders, cottage gardens, coastal gardens, or naturalized areas. Red Valerian is excellent for planting in stone walls.