How to Grow Cirsium Plants in your Garden

Gardener's HQ Guide to Growing Plume Thistle, Scotch Thistle, and other Thistles

Thistles are thought of as weeds by many people.

However with them being the symbol of Scotland many people away from home with thoughts of the highlands like to grow them.

Despite them being spiky in nature Cirsium have pretty heads of purple that can be dried.

Cirsium arvense
Cirsium arvense – Field Thistle.

Cirsium vulgare
Cirsium vulgare, both photographs by Matt Lavin.

They make great plants for a wild garden.

Cirsium also known as the Scotch thistle can reach a metre in height.

Cirsium Growing and Care Guide

Common Names: Plume Thistle. Thistle: Pasture; Spear; Scotch; Clustered; Ashland; Slough; Peregrine; Field; Meadow; Fountain; Summer; Swamp.
Life Cycle: Hardy perennial, or biennial that is usually grown as a hardy annual by gardeners.
Height: 30 to 80 inches (50 to 200 cm).
Native: Asia, Europe, North Africa, North America.

Growing Region: Zones 3 to 10.
Flowers: Summer and early autumn.
Flower Details: Purple, pink, yellow, cream, white. Feathered hairs.
Foliage: Prickly leaves, deeply lobed.

Sow Outdoors: 1/8 inch (3mm). Following last frost or autumn. Spacing 12 to 24 inches (30 to 60 cm).
Sow Indoors: Germination time: two to three weeks. Temperature 70°F (21°C). Two weeks before expected last frost. Transplant outdoors following the last frost.

Requirements: Full sunlight or light shade. Good drainage. Moist soil.
Family: Asteraceae / Compositae
Miscellaneous: Some species have culinary use.

How to grow Scotch thistle - Cirsium

The seeds of scotch thistles can be sown in either autumn or after the last frost of spring. They should be sown at a depth of 3 mm (1/8th inch).

If started to be grown indoors first, then Cirsium takes about two to three weeks to germinate at a temperature of 21 to 24 degrees Centigrade (70 to 75°F).

The seedlings should be planted out in early spring, when it is still possible to get a frost with a spacing of about 60 cm (2 feet).

They can grow in either partly shaded or sunny parts of the garden that has good drainage.

Scotch Thistle pretty much cares for itself.

Common Questions

How many members does the Cirsium genus have?

The Cirsium genus has around 60 to 200 species, depending on the taxonomy system used. They vary greatly in morphology and habitat requirements.

Do members of Cirsium make a good garden or landscaping plant?

Some Cirsium species make good garden plants, especially in wildflower meadows and pollinator-friendly gardens, thanks to their attractive, nectar-rich flowers.

Which Cirsium species are most frequently grown by gardeners?

The most frequently grown species is Cirsium rivulare (Brook Thistle), valued for its feathery foliage and bright flowers.

Are members of the Cirsium plant genus fragrant?

No, members of the Cirsium genus are not known for their fragrance, but rather for their interesting form and vibrant flowers.

What is the perfect location to grow Cirsium?

Cirsium prefers full sun or partial shade and thrives in well-drained soil. They tolerate a variety of soil conditions and are relatively drought-resistant.

Is Cirsium invasive in the USA?

Yes, certain species like Cirsium arvense (Canada Thistle) are invasive, particularly in the northern states, due to their prolific seed production and aggressive growth.

How do I remove Cirsium plants from my garden?

Removal of Cirsium involves cutting before seeding, hand-pulling, or using specific herbicides. Ensure to remove all root fragments as they can regrow.

Summary

The Cirsium genus, part of the Asteraceae family, is native to regions across the globe. These biennial or perennial plants, known as thistles, are recognized for their spiky foliage and thistle-like, pink or purple flowers that bloom in summer.

Cirsium should be planted in a sunny location with well-drained soil. They can be grown from seeds sown in spring or fall. Regular watering is needed, but they are fairly drought-tolerant once established. Given their aggressive nature, they may require control to prevent them from becoming invasive.

I hope that you enjoyed this guide on how to grow Cirsium plants. You may also enjoy the following Gardener's HQ Asteraceae growing guides: How to grow Wormwood and Xanthium strumarium plants.