Name: Eryngium x zabelii ‘Big Blue’ aka big blue sea holly
Type of Plant: A striking perennial for full sun and well-drained soil. Hardy in Zones 5 to 9.
Why I Love/Hate this plant Big blue sea holly is an upright variety of a perennial plant with thistle-like flowers. Some varieties of Eryngium can flop, but if planted in full sun and grown on the leaner side (less water, no fertilizer) this one is upright and strong. The flowers are almost electric blue, and the bees adore them.
A Word to the Wise: This plant is most striking in late June and early July. After flowering it doesn’t bring much to the perennial party, so plant it behind some taller growing annuals, perhaps, so that once it’s finished the foliage is a bit hidden.
Do not grow this plant where it gets hit by frequent irrigation and do not fertilize annually. This makes a good cut flower, but you might want to wear gloves and long sleeves when you cut the stems because of the prickly nature of the leaves and flowers.
The color on the flowers lasts longest in areas where the nights are cool but the days are sunny…perfect for Cape Cod.