Eryngium ‘Big Blue’
More commonly known as sea hollies, eryngiums are one of the most eye-catching garden plants, prized for their spiky, typically blue, thistle-like flowerheads, each one surrounded by a pointy ru . The summer flowers are a magnet for pollinating insects, eventually fading to shades of bu in autumn and then providing interest as the weather turns cold and frost highlights the intricate detail of their architectural seedheads.
This is a big and diverse genus, comprising plants that hail from all over the world, where they grow in a range of di erent habitats. This presents gardeners with lots of exciting opportunities, but it can also cause problems when it comes to giving eryngiums the right conditions. “We often get people telling us they can’t grow them,” says National Plant Collection holder Brian Pike. “My tip is to research where the plant grows in the wild. In general, the Old World ones – such as Eryngium bourgatii, E. planum, E. giganteum and E. x zabelii hybrids – will be happy in a sunny position with good drainage and average soil. They don’t want to be waterlogged in winter, but they do need a wet spring, so water them if the weather is dry.”
Eryngium ‘Big Blue’ is a superb selection, with sti , upright stems bearing flowers in a shade of steely, metallic blue. Since they thrive in hot, sunny spots and free-draining soil, eryngiums are a great candidate for a gravel garden, where they’ll make a striking, architectural impact, and possibly seed around – eryngium seedlings look like docks at first, so if you want to keep them, be careful not to weed them out by accident. Team them with other plants that are at home in sunny spots, with contrasting colour and form.