PlantFiles: Sea Holly
Eryngium planum

This is growing in a poor, somewhat shady area in my yard. Flowers are very interesting; almost look spraypainted!

Blooms mid June to late July in my garden.

I beliewe that this plant has been grown in Finland for decades if not over a century, it is even too weedy in zone 4, propably even 3. But it is unusual (despite being so common), and removing the seedheads is really not a big trouble - and they make nice cutflowers even at late age. You just have to remember to cut them off, othervise your rockery will be run over by them. I grow it with my grasses, and so far I have left a few blooms to set seed to give the single plant a change to make a few daughters. This species is perhaps underestimated, as it lacks the beuty of some of the other eryngiums. I like the leaves, too.

Add another zone 4 survival here. I know it's rated zone 5, but it seems to be holding it's own in zone 4.

I grow the cultivar "Blaukappe" (Blue Cap), which gives steel tiny silver-blue flowers arranged in round clusters. After flowering the heads become a steel blue and can be cut and dried for use in arrangements. My plants here in zone 5 generally grow to about 2.5' and branch nicely. Looks pretty and contrasts nicely next to lambs ears.

Eryngium has an extremely long taproot and so it is hard to move a larger plant. I have had success with moving smaller "babies" which have self seeded close by. You must dig down quite far and remove as much as the taproot as possible - pot or plant immediately. I have had success in giving away several of the babies - or moving to new locations in this manner. Best to move in early spring. Foliage is a nice deep green and grows close to the ground. Needs full sun and very well drained soil. If soil drainage is optimum, can live through months with rainfall exceeding at least 7."

I want to add a note of interest on this plant. Despite a harsh zone 4 winter in Minnesota (-20°F and below with no snow until the end of summer) and their being entirely unprotected an on an exposed boulevard, the nine plants that successfully took from seed last year (no bloom of course) have returned and are now starting to bloom. I didn't notice the Zone 5 specification on the seed packet until this year!

Go figure, I have supposedly hardy plants that just up and died despite all manner of pampering, and these babies defy all odds to return.

I have them planted with yarrow, quaking grass, Bells of Ireland, moss roses, and sedum. Looks pretty good.

Easily grown in dry, sandy, well-drained soils in full sun. Tolerates poor soils. Self-seeds in optimum growing conditions. Tall plants tend to sprawl, particularly if grown in overly fertile soils or in anything less than full sun. This is a taprooted plant which transplants poorly and is best left undisturbed once established.