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Eryngium

Common Name: Miss Willmott's Ghost, Sea Holly

Overview

Cultivars

Big Blue

• Plants are long-blooming.
• Stake flowers when it grows tall.

Miss Willmott's Ghost

• Tall biennial
• Increasingly thorny and thistle-like as it comes into bloom.
• Impressive on moonlit nights.
• After it blooms, it dies.
• Taproot plant; transplants poorly.
• Year 1: Basal rosettes form that over-winter as evergreen rosettes.
• Year 2: Plant sends up flowering stems.

Ongoing Management

Fertilization

Not necessary to fertilize this plant, but can fertilize the plants in spring with a balanced fertilizer.

Watering

• Plant is drought tolerant.
• Withhold water in Fall.

Pruning / Cutting Back

• Deadhead to preserve a neat appearance and encourage new blooms.
  • Or, if left to dry, they make pretty dried flowers.
• Prune plant near ground level @ the end of the growing season. Mulch with pine needles.

Site Selection & Preparation

Eryngium plants prefer well-drained soil and full sun.

1. Amend the soil with compost or other organic matter to improve drainage and fertility.
2. Plant the seedlings at the same depth they were growing in their pots.
3. Space the plants according to the mature size of the species.
4. Water the plants regularly, especially during dry periods.

Propagation

Sea Holly

• Self-seeding may happen under satisfactory growing conditions, but rarely becomes a nuisance.
• Propagation is prohibited for Eryngium x zabelii (Big Blue)

Miss Willmott's Ghost

• Taproot plant; transplants poorly.
• Tall biennial
  • Year 1: Basal rosettes form that over-winter as evergreen rosettes.
  • Year 2: Plant sends up flowering stems.
• Self-seeding may happen under satisfactory growing conditions, but rarely becomes a nuisance.

Seed Collection and Storage

1. Allow the flower heads to dry on the plant completely. The seeds are typically ready for collection when the flower heads turn brown and the seeds begin to loosen.
2. Cut the entire flower head and place it in a paper bag. Shake the bag gently to release the seeds.
3. Separate the seeds from the chaff. A fine-mesh sieve can be helpful for this process.
4. Spread the cleaned seeds on a tray in a cool, dry place for a few days to ensure they are thoroughly dry.
5. Store the dried seeds in an airtight container in a refrigerator. This helps to maintain seed viability for a longer period.

Prior to Planting

To overcome seed dormancy, Eryngium seeds typically require a period of cold stratification. This process mimics the natural winter conditions that the seeds would experience in their native environment.

1. Moisten the paper towels and wring out any excess water.
2. Place the Eryngium seeds on the moist paper towels.
3. Fold the paper towels over the seeds.
4. Place the wrapped seeds in a resealable plastic bag or container.
5. Label the bag with the date and species of eryngium.
6. Place the bag in the refrigerator (not the freezer) for 4-8 weeks. The ideal temperature is around 4°C (39°F).
7. Check the seeds periodically to ensure the paper towels remain moist. If they dry out, lightly re-moisten them.

Sowing Eryngium Seeds

After cold stratification, the Eryngium seeds are ready for sowing.

• The best time to sow eryngium seeds is in early spring, after the cold stratification period.
• Use a well-draining seed-starting mix. A mix of peat moss, perlite, and vermiculite is ideal.
• Process
  1. Fill seed trays or pots with the growing medium.
  2. Moisten the growing medium thoroughly.
  3. Sow the eryngium seeds thinly on the surface of the growing medium.
  4. Lightly cover the seeds with a thin layer of the growing medium or vermiculite. Eryngium seeds require light to germinate, so avoid burying them too deeply.
  5. Gently water the seeds using a spray bottle or misting nozzle to avoid disturbing them.
  6. Cover the seed trays or pots with a clear plastic lid or plastic wrap to maintain high humidity. This helps to prevent the seeds from drying out.
  7. Place the seed trays or pots in a bright location with indirect sunlight. Avoid direct sunlight, which can overheat the seeds.
  8. Maintain a temperature of around 18-24°C (65-75°F) for optimal germination. A heat mat can be helpful in maintaining a consistent temperature.

Germination and Seedling Care

Eryngium seeds typically germinate within 2-4 weeks, depending on the species and environmental conditions.

1. Check the seed trays or pots regularly for signs of germination.
2. Once the seedlings emerge, gradually increase ventilation by opening the plastic lid or plastic wrap for a few hours each day. This helps to prevent fungal diseases.
3. Water the seedlings regularly, allowing the growing medium to dry slightly between waterings. Avoid overwatering, which can lead to root rot.
4. Provide the seedlings with plenty of bright, indirect sunlight. If natural light is insufficient, use grow lights.
5. Once the seedlings have developed their first true leaves, begin fertilizing them with a diluted liquid fertilizer every 2-3 weeks.
6. Once the seedlings are large enough to handle (typically when they have 2-3 sets of true leaves), they can be transplanted into individual pots. Use a well-draining potting mix.

Hardening Off

Before planting the seedlings outdoors, it’s essential to harden them off to acclimate them to the outdoor environment.

Winter Protection

In colder climates, provide winter protection by mulching around the base of the plants.

More Information

Web Sites

• Gardenia.net - Eryngium
  • Gardenia.net - Eryngium Big Blue
• Missouri Botanical Garden - Eryngium giganteum