Red valerian is the common name for Centranthus ruber, an easy-to-grow, old-fashioned perennial that produces bright clusters of small, star-shaped red, pink or white flowers above bluish-green foliage. It is native to Europe and parts of Africa but is grown in flower gardens throughout the world. Common names for this plant include Jupiter’s beard, drunken sailor and keys to heaven.
These highly ornamental plants will grow where nothing else will and are a good choice for areas with dry or poor soil. They do not require a lot of water or care and will spread rapidly, sometimes to the point of becoming invasive. This can be discouraged by removing the dead flowers promptly, because red valerian self sows. The seed heads are similar to those of the dandelion and are carried in the wind. They will become volunteer seedlings, turning up everywhere the following year, if these plants are allowed to set seed.
Red valerian can grow quite tall, often reaching 3 feet (91 cm) in height, making it a good choice for the back of the garden border. They are perfect for wildflower and cottage gardens where they are given plenty of room to spread out. They should be planted where they are exposed to bright sunlight for most of the day for optimum flowering and growth and the brightest color.
When red valerian plants become very large, they can easily be divided to create several smaller plants. They should be watered and cut back so the stems are about 6 inches (about 15 cm) tall before they are dug up. These garden plants form thick, deep roots, so it is important to dig deep to get as much of the root system as possible. The roots should be cut into at least two sections with a sharp knife, though more divisions may be cut if the roots are very big. These pieces can be planted immediately in a sunny spot and should be kept watered until they are established.
It also is easy to grow these perennial plants from seed. The seeds should be barely covered with rich soil and kept moist until they germinate, which takes about two weeks. The seedlings should be planted outdoors when the nighttime temperatures do not drop below freezing, because red valerian will not survive extremely cold temperatures. First-year plants will usually produce flowers during the summer and may bloom again in the fall if they are cut back after the summer flowering is done.