Sea Holly
Eryngium giganteum
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Eryngium giganteum The silver-blue petals of sea holly waft ethereally almost hip-high in the flower bed. And, most likely, you'll find it over in the border, near the foundation plantings, and maybe even in the vegetable garden. Because, although this ghostly giant is a biennial, the plant is more than generous in seeding. As well as flowering its second season and then -- pfft -- going toes up, sea holly actually multiplies. Sea holly seeds so reliably, in fact, that many seasoned gardeners are still convinced the plant is a perennial. Look, it comes back in the same spot year after year. You may think what you wish. We are quite accommodating in this corner of the garden.

Eryngium giganteum is sometimes said to be a bit thirstier than most border plantings. We have not found this to be the case, but if you are of a mind, give it an extra squirt in high summer. And some texts go so far as to say sea holly seedlings resist transplanting. Two things: 1) We have not found this to be the case. At all. And 2) what if it were? You transplant 20 gorgeous ghostly gray plants and only 10 survive? You are still way ahead in our book. Oh, and while you're out transplanting, put three over by that too-big swath of large purple flowers, OK?

Light: Full sun. Hardiness: To 25 degrees below zero. Growth habit: 3 feet tall. Bloom time: Mid- to late summer.