Blue globe thistle

Blue globe thistle: how do you recognise it?

Habit

Upright, sturdy clump 1–1.2 m tall and about 60 cm wide, with branched, grey-downy stems.

Leaves

Deeply cut, thistle-like leaves with spiny teeth; grey-green above, white and felted beneath.

Flower

Spherical flower heads up to 5 cm across, made up of many tiny tubular flowers, from July to September.

Colour

Steel blue to blue-violet; the young buds are silvery grey.

Roots

A deep, fleshy taproot: it makes the plant drought tolerant, but it does not like being moved.

Seed

After flowering, brown seed heads that stay standing in winter; it sometimes self-seeds.

Flowering: July–September · Plants: March–April and September–October · Pruning: March

Why grow it?

• A magnet for bees, bumblebees and butterflies, which crowd the globes from July to September.
• Strong shape: the round, steel-blue globes give structure to a sunny border or gravel garden.
• Drought tolerant thanks to a deep taproot: in dry summers it hardly needs watering.
• An excellent cut flower, fresh or dried; cut just before the globes are fully open, they keep their colour.
• Leave the seed heads standing and birds such as goldfinches come to eat the seeds in autumn and winter.
• Fully hardy and seldom troubled by disease.

Blue globe thistle: where does it grow best?

• Full sun is a must: in shade the stems become floppy and it flowers less.
• Light, free-draining soil: sand or loam, acid to chalky. In heavy, wet clay the root rots in winter.
• Dry soil: poor soil gives sturdier plants than rich, fertile soil.
• An open spot with plenty of light and air; it does very well in a gravel garden or in front of a warm wall.
• Plant 50–60 cm apart, about 3 plants per m², in the middle or at the back of the border.

Light

Sun

Soil type

Sand or loam

Acidity

Not fussy

Moisture

Dry

Size

1.2 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Sea holly: Even more steel blue and spiky shapes, in the same dry, sunny spot.
• Russian sage: A haze of lavender blue at the same time, and just as drought tolerant.
• Yarrow: Flat heads in yellow or terracotta, contrasting with the round globes.
• Feather grass: Soft, swaying stems beside the stiff, spiky shape.
• Coneflower: Pink or white flowers in the same summer months, also loved by bees and butterflies.

Blue globe thistle: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or in September–October, when the soil is neither frozen nor waterlogged.
2. Dig a deep planting hole, at least twice as deep as the pot, so the taproot can easily grow down.
3. On heavier soil, mix coarse sand or fine gravel into the soil for better drainage; compost is not needed.
4. Set the plant at the same depth as it was in the pot, firm the soil and leave 50–60 cm between plants.
5. Water in well straight away and again during dry spells in the first weeks; after that it looks after itself.
6. Use a thin layer of gravel rather than compost around the base: it keeps the crown dry.

Care

Water

Only in the first year, during dry spells. After that, extra water is rarely needed, even in dry summers.

Feeding

Not needed. Fertiliser makes the stems long and floppy.

Support

In a sunny, poor spot it stands without help. In rich soil or partial shade, a few canes or a ring help.

Spent flowers

Cut them off if you do not want seedlings, or leave them for the birds and for winter interest.

Gloves

Wear gloves when you work on the plant: the leaves and flower heads are prickly.

Leave it be

Avoid moving it: the taproot breaks easily and the plant is slow to recover.

Tip: For a dried bouquet, cut the globes just before they are fully open: they stay deep blue and do not fall apart.

Blue globe thistle: when to prune it?

Pruning months: March.

When: Cut the dead stems away in March, just before new growth starts. In summer, only cut flowers for the vase or remove spent globes.

How:

• In March, cut all old stems down to just above the ground, above the young leaves.
• Wear sturdy gloves: the old stems and leaves are prickly.
• In summer, remove spent globes if you want to avoid seedlings.
• For dried flowers, cut long stems just before the globes are fully open and hang them upside down to dry in a dark, airy place.

Caution: Do not cut off the seed heads in autumn if you want to help the birds: goldfinches eat the seeds in winter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Root cuttings

In winter, from December to February: cut 5–8 cm pieces from a thick root and push them upright into a pot of gritty cutting compost, with the top just below the surface. Keep them cold but frost-free.

Seed

Collect ripe seed in autumn and sow it in a pot in a cold frame. Seedlings usually flower from the second year; cultivars do not always come true from seed.

Division

In spring you can carefully divide an old clump, but because of the taproot it does not always take.

Blue globe thistle: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Belgium.
• In winter, wet feet are a bigger danger than frost: on heavy, waterlogged soil the root rots.
• Leave the stems until March: covered in frost the globes are a winter feature, and birds eat the seeds.
• In a deep pot with free-draining compost it can overwinter outdoors; keep the pot dry, for example under a roof overhang.

Diseases and pests

• Aphids: On stems and buds in early summer. Ladybirds usually clear them up; otherwise spray them off with water.
• Powdery mildew: White powder on the leaves in late summer, especially in dry weather. Usually harmless: cut off affected leaves and give the plant room.
• Root rot: The plant collapses or fails to reappear after a wet winter. Plant in free-draining soil, perhaps slightly raised, and do not feed.
• Slugs: They eat the young shoots in spring. Pick them off in the evening and protect young plants for the first few weeks.
• Seedlings: It self-seeds into gravel and bare soil. Remove spent globes or pull out young seedlings early.

Through the year

• January: Rest. Take root cuttings.
• February: Take root cuttings. Leave seed heads for the birds.
• March: Cut away old stems. Plant.
• April: Plant. Protect young shoots from slugs.
• June: Watch for aphids. Support plants in rich soil.
• July: Flowering begins. Cut globes for drying.
• August: Full flower. Remove spent globes if you do not want seedlings.
• September: Last flowers. Plant.
• October: Plant. Collect seed and leave the seed heads standing.
• December: Rest. Frosted stems decorate the garden.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• The name Echinops comes from the Greek echinos (hedgehog) and means roughly ‘looking like a hedgehog’: the spiny globes resemble a hedgehog rolled into a ball.
• Each globe is made up of dozens of tiny heads, each holding just one flower, packed tightly together into a perfect sphere.
• The species name bannaticus refers to the Banat, a region now divided between Romania, Serbia and Hungary.