The delicate foliage and the fluorescent color of the flowers make Greek valerian a favorite for shady areas. Direct seed in early spring and it will grow tall and start blooming in mid-spring, sometimes continuing into early summer so you can continuously enjoy these fragrant and wildlife-resistant plants. These plants are easy to grow from seed, and they will very easily self-seed and spread in an uncontrolled (but not invasive) fashion in the garden unless the spent flowers are removed before seeds can fall.
Light
Greek valerian plants prefer partial or dappled shade. Varieties with dark green leaves can handle more direct sun than the variegated varieties, so long as the soil is kept consistently moist.
Soil
Plant Greek valerian in loose, rich, well-draining soil that will remain moist but not wet. It is fussier about moisture than about soil pH but does best with a relatively neutral or slightly acidic soil pH.
Water
Greek valerian plants that receive regular watering will bloom longer and remain attractive into summer. Water regularly to maintain medium moisture levels but avoid soggy conditions. During dry periods, you may need to water more frequently to keep the plants lush.
Temperature and Humidity
Greek valerian prefers a relatively cool summer climate, and it can succumb to high heat in warm southern gardens. Very humid conditions can bring on leaf spot fungal diseases or powdery mildew.
Fertilizer
Polemonium caeruleum is a long-lived perennial in the right conditions and if it is fed properly. Give the plants a boost in early spring with a dose of balanced fertilizer as the new growth is emerging. Feed them again once the faded flowers have been cut back.
Types of Greek Valerian
Look for these kinds of Greek valerian for your garden:
Polemonium caeruleum’ Album’: This variety has white flowers.P. caeruleum ‘Bambino Blue’: Beautiful light blue flowers adorn this variety.P. caeruleum ‘Snow and Sapphires’: With variegated leaves and blue flowers, it is somewhat hardier than the similar Brise d’Anjou.P. reptans ‘Stairway to Heaven’: This variety exhibits blue flowers on variegated foliage that blushes pink in cool weather.
Pelamonium Reptans vs. P. Caeruleum
A closely related plant is Pelamonium reptans, a native wildflower of eastern North America. It has a similar appearance to P. caeruleum, but it is somewhat shorter and even more tolerant of cool conditions. It is a short-lived perennial, however, often behaving as a biennial. The native species is rarely planted in gardens, but there are some good cultivated varieties available, including ‘Blue Pearl’ and ‘Brise d’Anjou’. Despite the name, this plant does not spread by creeping rhizomes, but it spreads readily by self-seeding.
Pruning
In general, Greek valerian requires minimal maintenance. Once the flowers finish blooming, cut the flower stalks back to the plant’s base to encourage repeat blooms. If the foliage starts to look tattered, it can also be cut back and cleaned up. New growth will replace the trimmed foliage.
Propagating Greek Valerian
Greek valerian propagates easily by being divided. Mature Greek valerian plants should be divided every three to four years, or they will start to die out in the center. They divide most easily and successfully in early spring. Here’s how:
How to Grow Greek Valerian From Seed
If you already have a Greek valerian plant, it will self-seed on its own from seeds dropped from flower heads. You can also collect the seeds to replant elsewhere. Greek valerian can be direct seeded in either spring or fall. Loosely cover the seed with soil, then water. Keep the soil moist, and be sure to mark the spot so that you do not disturb it. To start seed indoors, sow two months before your last frost date if you want to transplant in spring, or sow in mid-summer if you want to transplant in the fall. The seeds take up to a month to germinate and should be kept moist until then. Transplant outdoors in spring just before your last frost date, or in early to mid-fall.
Overwinterizing
Prepare this plant for winter by cutting it down completely in the fall after the first frost. After cutting it, place a thin layer of compost over the roots as this will help make the soil nutrient-rich, preparing it for the spring.
Common Pests & Diseases
Greek valerian plants are generally problem-free, but there are a few pests and diseases that will attack, particularly if the plants are stressed. The most common problems are sun scorch and insufficient water, which cause the leaf tips to start browning. Other potential problems include:
Leafminers: Control leafminers by removing affected leaves and/or by treating them with neem oil. Slugs: Eliminate slugs with various homespun methods (such as tuna cans or eggshells) or apply an organic treatment (such as diatomaceous earth or a natural commercial repellent). Leaf spot: Prevent leaf spot by pruning to ensure good air circulation and watering in the morning so the foliage dries during the day. Powdery mildew: Control powdery mildew by keeping the foliage dry (water the ground, not the leaves), pruning for good air circulation, removing affected leaves (as practical), and applying a fungicide as needed.
How to Get Greek Valerian to Bloom
Greek valerian blooms mainly in the mid-spring and summer, but to hopefully extend the flowering of these delicate fragrant flowers and get a second blooming period, deadhead any spent flowers from the first bloom. The soil should be kept moist, not soaked, as this will also help lengthen the flowering time.
