Essentials
At a Glance
Plant Type
Perennial
Height
24 inches
Width
18 inches
Light
Full Sun, Partial Sun
Zones
4, 5, 6, 7, 8, 9
Water
Low
Humidity
Low
Lifespan
Perennial
Native To
Europe and Central Asia
Toxicity
Non-toxic to humans and pets
The Story
Plant Bio
Eryngium planum, commonly known as blue sea holly, is known for its spiky, blue foliage and unique flower heads. Notable for its resilience to drought and ability to thrive in poor soil conditions.
Bloom Period:
Uses & Benefits:
Marketplace
Where to Buy
Shipping costs Year-round shipping Free shipping
Planting
How to Grow
- Select a sunny location with well-draining soil.
- Tuck seeds just below the soil surface and water lightly.
- Maintain consistent moisture until germination, about 2 weeks.
- Thin seedlings to 12 inches apart once established.
- Mist cuttings in early spring for propagation, keeping soil moist.
- Mulch around plants to suppress weeds and retain moisture.
Pro Tip
Ensure excellent drainage to prevent root rot and encourage healthy growth.
Keep It Thriving
Care Guide
Do
- Water deeply during dry spells 💧
- Prune dead or damaged stems in late winter ✂️
- Apply a balanced fertilizer in spring 🌱
- Mulch to conserve moisture and suppress weeds 🌿
Don't
- Avoid overwatering to prevent root rot ❌
- Don't fertilize in late fall ❌
- Refrain from disturbing roots during growth ❌
- Never leave soil compacted around plants ❌
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Divide | ||||||||||||
| Harvest | ||||||||||||
| Plant | ||||||||||||
| Spring Cleanup |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Companion Plants
Multiply
Propagation Methods
Good to Know
Common Questions
Flat Sea Holly questions
What zones can Flat Sea Holly grow in?
Flat Sea Holly is hardy in USDA Zones 4–9. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Flat Sea Holly deer resistant?
Yes — Flat Sea Holly is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.
When does Flat Sea Holly bloom?
Flat Sea Holly typically blooms in mid-summer through late summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Flat Sea Holly need full sun?
Flat Sea Holly does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
Is Flat Sea Holly drought tolerant?
Yes — once established (usually after the first full season), Flat Sea Holly handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.
More Eryngium to compare
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Eryngium yuccifolium
Big Blue Sea Holly
Eryngium x hybrida 'Big Blue'
Sea Holly
Eryngium elevatum
Blue Glitter Sea Holly
Eryngium planum 'Blue Glitter'
Blue Hobbit Eryngium
Eryngium x zabelii 'Blue Hobbit'
Picos Blue Sea Holly
Eryngium bourgatii 'Picos Blue'
Keep exploring
Explore the genus
Collections featuring this plant
Grow Flat Sea Holly with confidence
See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.
