Members of the Eryngium genus are hardy and half hard perennials.
They have spiny leaves of blue or grey and spiky white or blue flowers that bloom in the second part of Summer.
Depending on the species they can range in 30 cm to 1.2 m in height and therefore make great plants if you want something a little bit unusual in the garden border.
Some common names Eryngium include Sea Holly, Spiny cilantro and Eryngo.
Common Names: Eryngo, Sea Holly, Rattlesnake master.
Life Cycle: Hardy perennial. Half hardy perennial.
Height: 12 to 48 inches (30 to 120 cm).
Native: Europe, Asia, Northern America.
Growing Region: Zones 3 to 10.
Flowers: Middle to late summer.
Flower Details: White, blue, greenish. Cone-shaped. Spiky. Tight umbels.
Foliage: Prickly. Yucca-like. Silver, blue. Basel rosette.
Sowing: Surface. Germination time: one week to three months.
Seed: Method 1: Seeds should first be sown into flats in the autumn. Next sink the flat into the ground in an area that offers shade, preferably close to a wall that faces north. Provide a glass/plastic covering. Keep an eye on the flats to ensure that the soil remains moist. Bring the flats indoors at the beginning of spring and keep at 65 to 75°F (18 to 24°C). Transplant seedlings when they are strong.
Seed: Method 2: Mix seeds in a moist growing medium, then put in flats, wrap in a large plastic bag, then stratify by refrigeration for three weeks. Next bury the flat as described above. Once seedlings emerge transplant them to their final location.
Requirements and care: Full sunlight. Good drainage. Poor soil. Soil pH 5.0 to 7.0. Water during prolonged dry spells. Provide support if needed. Winter gravel mulch. Propagate: by taking root cuttings in the spring.
Miscellaneous: Has long taproots. The species Eryngium yuccifolium gets its common name of Rattlesnake master because it was used as a traditional native Indian cure for snake bites in Northern America.
If you plan to grow Eryngium species such as Sea holly from seed then first they should be planted into a flat within a black bag (in the spring), then placed in the fridge for three weeks. The flat should then be sunk into the ground in a shady location of the garden. germination usually takes anything from one to ten weeks. Once you get Sea Holly seedlings they should be transplanted into an area of the garden that is sunny with good drainage. Sea Holly likes to grow in a soil that is light and slightly acidic to neutral (pH 5 to 7). It is best to space smaller Eryngium at about 40 cm apart and larger ones at between 75 and 90 cm apart.
If you require more Eryngium plants then cuttings can be taken in the spring. Sea holly can pretty much look after themselves but give it a little water in prolonged dry spells and stake larger varieties to protect them from the wind.
I hope that you enjoyed this guide on how to grow Eryngium plants. Updated September 2020.