Eryngium planum
Flat-leaved Sea Holly
Common names: Steel-blue Sea Holly, Blue Sea Holly
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Description
Eryngium planum is a thistle‑like perennial with steel‑blue shimmering foliage and globular flower heads. From July to September it turns sunny beds into a blue sea of blooms, attracting many bees and bumblebees. The plant originates from southeastern Europe and Central Asia and is tolerant of dry, poor soils. Its long vase life makes it a popular cut flower for bouquets and winter arrangements. It is a purely ornamental plant and is not used in kitchen or children’s gardens.
Care instructions
Plant in full sun on well‑drained soil; it tolerates longer dry periods well. Water regularly only during the first few weeks after planting; thereafter rainwater is usually sufficient. On heavy, water‑logged soils add a drainage layer of sand or gravel to prevent root rot. Leave the fruiting heads over winter; they look attractive with frost and provide shelter for insects. For dried bouquets, cut stems just before full bloom and hang them upside down in a well‑ventilated, shaded area.
Soil & site
Soil pH
Soil type
well-drained, lean, sandy, lime-loving
Feeding
Light feeder
Companion planting
Good neighbors
amaryllis family (Amaryllidaceae)
Umbellifers and alliums confuse each other's pests (carrot fly, onion fly).
For example GarlicOnionLeekChivesDaffodilRocambole and 12 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
daisy family (Asteraceae)
Calendula and Tagetes next to carrots keep the carrot fly away with their scent.
For example Head lettuceTagetes patulaCalendulaSunflowerCommon coneflowerFall Aster and 57 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
cabbage family (Brassicaceae)
You can pair celery and dill with all Brassicaceae because they repel the cabbage whitefly with their scent, a proven companion.
For example White cabbageKohlrabiRadishKalebroccolicauliflower and 34 more species in the catalogue
Source: Bio-Gärtnerei Mixed-culture Practice
legume family (Fabaceae)
Peas and beans provide carrot and celery with nitrogen and grow as shallow-rooted plants without competition next to each other.
For example PeaBush beanPole beanBroad beanMarker peaSugar pea and 31 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
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