Sea Holly – Eryngiums

Plant eryngiums where there is bright light, poor soil and good drainage in order to develop a strong, rigid framework and steely patina.

These plants are good low-maintenance plants for hot dry spaces with good drainage.  If grown on damp, heavy soil most eryngiums tend to flop and become a dull, grey-green.

However, eryngiums are very diverse: there are over 240 species worldwide.  Try growing one or two sea holly in the driest hot spots you have.  Some even do well on clay.

allotment-sea-holly-thistle-bee

Sea Holly with Bee on Allotment, 7 July 2018.

Sea hollies are an unusual member of the carrot family (Apiaceae).   They set down deep tap roots and do not like to be moved once planted.   Plants can grow up to 3 feet tall. The plants die down completely in winter and, given good drainage, will return every year. 

  • Water sea holly plants deeply, but infrequently during the first season of growth to encourage the tap root to grow deep into the soil (which is the key contributor to sea holly survival during droughts).  Otherwise, they thrive happily on benign neglect.  In fact, fertile soil makes plants lanky, so withhold fertilizer and extra watering.
  • Deadheading won’t yield additional blooms. Indeed, faded flowers add winter interest long after the first frost occurs, so it is advised to avoid deadheading.  The seedheads last well into winter and add visual interest.

As with many blue flowers, sea holly (eryngium attracts butterflies. If you use this in a coastal garden, consider planting your eryngiums near a fence or building to provide a butterfly-friendly windbreak.

The genus Eryngium belongs to the Apiaceae plant family.  This family contains edible plants like sweet fennel as well as poisonous plants like the water hemlock. The common denominator of the Apiaceae family is that the plants have hollow stems, and that they produce compound umbels, which are small flowers that radiate from a single stem.  From The Spruce

Some interesting sea holly trivia: the first known artist self-portrait in the history of Western art, by Albrecht Durer, shows him as a gallant, well dressed young man who is holding in his hand a sprig of sea holly.  In Germany sea holly signifies man’s fidelity and is sometimes considered to be an aphrodisiac.  Some art historians think that this portrait was painted as a gift to his betrothed Agnes Frey*, whom he married shortly after.

We planted a sea holly at the allotment the summer of 2018.  The big guy was worried it had died but we held off digging it out.  It has returned in 2019 but is not producing any flower heads and growth is low and slow.  We are trying to avoid over-watering as it is planted into heavy clay and probably has less-than-ideal-drainage for a drainage loving plant.  We’ve been quite disappointed but in early August 2019 we noticed a second plant that has appeared at the side of the main plant.  Hopefully this means it’s diverted it’s flowering energies to producing more plants, and will do much better next year.  We can only live in hope!