This grower is fairly sure of this plant identification.
Definitely sea holly but I lost the label so exact type is "probably" or "almost certainly".Grown from root cuttings taken this year.
Several available (I didn't expect them all to take!)
Giant sea holly, Sea holly
Eryngium giganteum ‘Silver Ghost’ (Giant sea holly). Small, white flowers are borne with grey-white bracts in mid-summer.
They are fully to half hardy. Grow in sun with fertile well drained soil.
Grown for their flowers, foliage and habit. Suitable for coastal conditions.
Italics = data drawn from parent genus or speciesView Full Plant Finder Record