Botanical Name: Eryngium planum
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Common Name: Blue Sea Holly  
Plant photo of: Eryngium planum
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Water Saving Tip:

Replace turf with groundcovers, trees, and shrubs. If you have areas where no one uses the grass, patches that do not grow well, or a turf area too small to water without runoff, consider replacing the turf with water-efficient landscaping.

  • Anatomy

  • Culture

  • Design

Plant Type

Perennial

 

Height Range

1-3'

 

Flower Color

Blue

 

Flower Season

Summer, Fall

 

Leaf Color

Blue Green, Grey Green, Silver, White

 

Bark Color

n/a

 

Fruit Color

n/a

 

Fruit Season

n/a

Sun

Full

 

Water

Low, Medium

 

Growth Rate

Moderate

 

Soil Type

Sandy, Clay, Rocky

 

Soil Condition

Average, Poor, Well-drained, Dry

 

Soil pH

Neutral, Basic

 

Adverse Factors

n/a

Design Styles

English Cottage, Mediterranean, Ranch

 

Accenting Features

Showy Flowers

 

Seasonal Interest

Summer, Fall

 

Location Uses

Perennial Border

 

Special Uses

Cut Flowers, Naturalizing

 

Attracts Wildlife

Birds, Butterflies

Information by: Stephanie Duer
Photographer: Susan Frommer
  • Description

  • Notes

One of the Eryngium speicies, with violet blue thistle-like flowers and grey-green leaves with a tinge of purple. A striking addition to a perennial border. Grows about 24 to 36 inches tall and half as wide. Tolerates drier soils than other sea holly.
Grow in well drained soil in full sun; tolerates poor sandy soils. Over-fertile soil or over fertilizing may cause plant to sprawl. This is a tap-rooted plant that transplants poorly once established and so is best left undisturbed. Plants are biennial, so in the first year, basal rosettes of foliage form that overwinter as evergreen rosettes. In the second year, plants send up flowering stems, produce flowers and seed before dying. As is the case with foxgloves (Digitalis) and hollyhocks (Alcea), these eryngiums will self-seed and remain in the garden from year to year as if they were perennial unless spent flower heads are deadheaded prior to seed drop. Stock purchased at nurseries is typically in its second year, though you may want to check.