I thought it was going to be easy to write up eryngiums but it transpires that there are a whole lot of different ones from various habitats and climates. So I will confine my comments to the ones we are growing here. I love these ethereal thistle or teasel-like flowers in the prettiest hazy blue. We have had what I think is Eryngium variifolium in the rockery for a number of years. Despite its decidedly prickly habit and its location too close to the path, the flowers are always a summer delight. When I tried to move it back from the path, I found it had a phenomenally long and tough tap root so it defied my plans. That one has never set seed for us. Some eryngiums are propagated by autumn root cuttings so we plan to try that.
Eryngium planum is taller so needs staking in the garden. It flowers earlier in the season and grows easily from seed. We ordered it through Kings Seeds and this is the first summer we have had a good sized planting of it. I am hoping it will set seed because I think I can use lots of this plant in the summer garden. It doesn’t take up much space so can grow through other plants and the flowers last a long time. Both forms we have are perennials. E. variifolium disappears entirely in winter but neither of us can remember whether E. planum does too or whether it retains a smaller rosette of visible leaves.
Eryngiums belong to the Apiaceae family (with carrots!) not the thistle family. They are often referred to as sea holly but that should more correctly be ascribed to E. maritimum which we have seen growing wild on the coast of Cornwall.
First published in the Waikato Times and reprinted here with their permission.