How to plant eryngiums

Also known as sea hollies, eryngiums produce rosettes of spiky bracts with cone-shaped centres and slightly spiky silver-green foliage. The thistle-like flowers of these striking hardy perennials will bring a sculptural elegance to most settings, especially dry and coastal gardens. Try mixing with agastaches, echinaceas, lavenders and lilies or interlace with grasses. Excellent cut and dried flowers, they can be used to add a little pizzazz to the Christmas decoration.

Plant in dry, poor to moderately fertile soil in full sun. After flowering, cut back to ground level. As they do not like winter wet, make sure to provide protection.

Eryngiums are supplied as bare-root plants. Always unpack and plant on arrival.

Potential problems, pests and diseases:

• Snails and slugs: these pests enjoy munching on young shoots, stems, leaves and flowers. Watch out for damage!
  
  
• Powdery mildews: these fungal diseases usually caused by planting in the shade or by poor air circulation can be seen in the form of white, powdery coating on the leaves. Cut off any infected material before disinfecting your scissors.
  
  
• Root rot: this soil-borne fungal disease occurs when the soil is too wet and can generally be spotted when foliage starts to yellow and plants begin to wilt and stunt. If left untreated, plants will eventually die. If you suspect an attack, gently remove the plant from the ground, shake off any excess soil and inspect roots for any signs of rot disease — infected material will be brown and mushy. If the plant appears to be infected but still has white, firm roots, cut away any badly affected material before gently cleaning the remaining roots under running water. Replant in fresh well-drained soil before disinfecting your scissors. It is advisable to destroy any badly infected plants.