Eryngium planum
Flat-leaved Sea Holly
Common names: Steel-blue Sea Holly, Blue Sea Holly
At a glance
- Light
- Full sun
- Pot size
- from 20 l
- Lifespan
- Perennial
- Flowering
- Jul–Sep
- Hardiness
- Hardy
- Origin
- Native to Germany
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This description was machine-translated.
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.
The care notes were machine-translated from German.
Garden year
FloweringJul–Sep
Soil & site
Soil pH
Soil type
well-drained, lean, sandy, lime-loving
Blue eryngo likes it lean and dry, as in its native sites in steppes and on dry grassland. A well-drained, sandy-calcareous soil without waterlogging is more important than richness in nutrients. On heavy, moist soils the taproot quickly rots, so drainage of gravel or sand helps when planting. Soil that is too rich also makes the stems soft and reduces the lovely steel-blue colour.
Feeding
Light feeder
As an undemanding steppe plant, blue eryngo needs practically no feeding. A thin helping of compost in early spring is entirely enough, and on lean soils you may even leave it out altogether. More important than nutrients is a warm, sunny spot with good drainage.
Overwintering
Blue eryngo is quite hardy and gets through frost without protection as long as its feet stay dry. The plant is more sensitive to wet in winter than to cold; a well-drained site spares you most worry here. You can leave the dead flower heads standing until spring; they look decorative with hoar frost and additionally protect the root zone.
Propagation
Methods
- From seed
- Division
- Cuttings
The easiest propagation is by sowing in late winter; for this the seeds need a cold period as a germination stimulus. Alternatively, older clumps can be divided in spring, injuring the deep taproot as little as possible. Root cuttings in early spring also root reliably. After planting, allow about two years of patience until the plant has properly established and flowers abundantly.
Companion planting
Good neighbors
amaryllis family (Amaryllidaceae)
Umbellifers and alliums confuse each other's pests (carrot fly, onion fly).
For example GarlicOnionLeekChivesWild daffodilRocambole 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 lettuceFrench marigoldCalendulaSunflowerButterhead lettuceCommon coneflower and 73 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 41 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 beanSnow peaWrinkled pea and 36 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.
Some of these explanations were machine-translated.
For your garden
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