In fact, it is not even related to holly (Ilex spp.) and looks like a grey-leaved thistle.
Sea holly, Eryngium maritimum, is a herbaceous plant that inhabits coastal sand dunes.
Eryngium maritimum can be found from Scotland to the Mediterranean and North Africa.
It grows in among the sand dunes and has evolved several adaptations to enable survival in this harsh environment. The grey leaves help reflect the hot sun, waxy leaves reduce water loss and the long taproot anchors it into the sand and reaches deep down for moisture. These adaptations make it a very drought-tolerant plant, great for a sunny, dry, free-draining spot.
Because of the long taproot it dislikes disturbance and needs to be planted in its final location as a small plant.
As well as the attractive grey-green foliage with prominent silver veins, it bears blue teasel-like flowers backed with large grey bracts in summer which persist well into the autumn.
This makes a long-lived display, great for cut flowers. It can be grown easily from seed, reaching 60cm tall when established.
Eryngium maritimum is growing on the lower side of the lowest path through the Mediterranean Garden at Dunedin Botanic Garden.
• Dylan Norfield is the Geographic and Arboretum Collection Curator at Dunedin Botanic Garden.
