Red valerian, Centranthus ruber, is a drought-tolerant herbaceous perennial that blooms all summer long and makes a good cut flower. Its sprays of small crimson, pink or white nectar-rich flowers are scented and attract bees, butterflies and other pollinators, in particular the fascinating humming-bird hawk moth (Macroglossum stellatarum).
Red valerian is not the same as the herb known as common valerian, Valeriana officinalis. While red valerian has no toxic effects it also has no medicinal value, whereas the root of common valerian is used in herbal medicine.
How to grow and care for red valerian
Grow red valerian in full sun in an informal, dry or wildlife garden, on walls and banks. It will flower from early summer through until early autumn, and even later in milder areas. Fading flowers should be cut back to avoid self-seeding.
Where to grow red valerian
Red valerian thrives in neutral to chalky, well-drained soils in full sun. It tolerates partial or lightly dappled shade but may not flower so prolifically. In rich soils or more shady spots, it may need staking. Growing to a height of 1m, with oval green leaves all the way up the stems, it makes a good mid-border plant, but it will also grow well in walls, gravel, rock gardens and seaside gardens.
How to plant red valerian
Red valerian is hardy and can be planted in autumn or spring, as well as in mild spells during winter. Plant it to the same depth as it was in its pot and, if planting in summer, water regularly over the first few weeks until established. Plant red valerian with other sun-loving cottage garden plants like sea holly (Eryngium maritimum), Oenothera lindheimeri, common harebell (Campanula rotundifolia), and perovskia.
How to care for red valerian
Red valerian is very easy to grow. It’s extremely drought tolerant and doesn’t need watering or feeding, even in poor soils. It’s a great coloniser, the wind carrying its fluffy seeds, so to limit its spread, cut back the flower heads before the seeds ripen. This will also encourage more blooms, extending the flowering period. Mature plants form clumps that slowly spread to up to 60cm across and become woody. It isn’t invasive, as young plants can be pulled up easily and older more established clumps can be lifted with a spade. If removing from dry stone walls, take care not to damage the structure.
How to propagate red valerian
Red valerian can be propagated by seed, division or basal cuttings. From March, sow seed indoors onto moist compost, lightly cover with compost and place in a plastic bag. Germination takes three to four weeks. When the seedlings are large enough to handle, transplant into larger pots and plant outside from late April, 30cm apart. Alternatively, from April onwards, sow seed outdoors where it is to flower. Remove any weeds, rake the soil and sow the seed sparingly, raking again to give it a light covering of soil. Some weeks after germination, thin the seedlings, keeping the most vigorous ones, to 30cm apart.
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If red valerian is already established in your garden, you can propagate it by division. As well as producing more plants, this technique can revitalise old plants, stopping the root system from becoming congested. In autumn, when the flowers have faded, or in spring, when new shoots are just emerging, dig up the whole clump using a garden fork. Shake off any surplus soil and use a spade or gardening knife cut the rootball into several segments, each with its own roots and stems. Remove the woody centre of the plant. Pot up any segments you want to give to friends and replant the remaining divisions in separate planting holes about the same size as the rootball. Water in thoroughly to settle the soil around the roots.
Finally, you can propagate red valerian by taking cuttings. In spring, when new shoots are about 15cm long, use a sharp knife to cut just below a bud. Take several cuttings, remove all but the top leaves on each stem and space the cuttings out in a pot of gritty free-draining compost. Cover the pot with a plastic bag and leave it in a cool, light position indoors. After germination, thin the seedlings to 30cm apart, keeping the most vigorous ones.
How to prune red valerian
No pruning is required. Cut back fading blooms to prolong flowering and limit the spread of seeds. In autumn, remove any dead leaves and compost.
Pests and diseases
Red valerian is generally pest and disease free and it isn’t eaten by deer.
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