Russian knapweed (Rhaponticum repens)

Russian knapweed

Also known as: Hardhead thistle

Rhaponticum repens is commonly called russian knapweed and is native to Eurasia. It has been introduced to North American and is a deep-rooted, long-lived plant. Some of these plants have been in existence for over 75 years.

Scientific classification

Species

Russian knapweed (Rhaponticum repens)

Asters bellflowers fanflowers and allies

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30 cm to 1.02 m

Plant Height

Green, Blue

Leaf Color

2.5 cm

Flower Size

Pink, Purple

Flower Color

Deciduous

Leaf type

Summer, Fall

Growth Season

Images of Russian knapweed

Distribution of Russian knapweed

Distribution Map

Russian knapweed has a native range that includes regions in Europe and Asia but has also been introduced to various territories across Europe and the Americas. While spread across continents, in certain areas, russian knapweed is sometimes thought to be a plant that may have an impact on local ecosystems due to its invasive potential. However, such effects are not universally observed and may vary by region.

Native

Cultivated

Invasive

Introduced

No species reported

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Habitat

Roadsides, Riverbanks, Irrigation ditches, Pastures, Waste places, Clearcuts, Croplands

Hemisphere Trend Curve

Northern

Sorthern

Weed Control

Russian knapweed is a perennial plant with deep roots. It is considered a serious crop weed in its native range and introduced areas.

How to Control It

Like other similar perennial weeds, russian knapweed is most commonly managed by depleting the food sources within its roots. This is achieved by removing aerial parts of the plant through cutting, mowing, disking etc. a number of times during the season, especially before the plant produces flowers and fruits. Russian knapweed is a very persistent plant, so this can be an ongoing battle. For this reason, it is advised to also plant some perennial grasses that can compete with russian knapweed and reduce its spread potential.

The use of herbicides is not advised. There are also some biological agents that can be used for russian knapweed control (e.g. the gall wasp Aulacidea acroptilonica, the gall midge Jaapiella ivannikovi). If you opt for biopesticides, consult an agricultural expert to find what is the best species for your geographical area.

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Quickly Identify Russian knapweed

Bright pink to purple thistle-like flower heads

Urn-shaped pink to purple flowers, transitioning to straw color

Ivory achene fruit with tufts of hair (pappus), <1 inch (2.5 cm)

Basal rosette leaves 2-4 inches (5-10 cm) long, pinnately lobed on stem

Distinctive paper-like bracts beneath flowers with spine-tipped scales

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Care Guide for Russian knapweed

Every week

Water

Full sun

Sunlight

Water: Originating from arid regions, russian knapweed exhibits high drought tolerance and requires weekly watering for optimal health. Thriving in well-draining soil that avoids waterlogging, russian knapweed is typically grown outdoors and benefits from conditions that mimic its native habitat's hydration patterns.

Fertilize: To boost russian knapweed's vigor and blooming, apply balanced fertilizer monthly during the growing season and reduce frequency when dormant. Use slow-release formulas for steady nutrients, and ensure to water russian knapweed post-application to enhance absorption and prevent root burn, adjusting seasonally for optimal health.

Pruning: Russian knapweed is invasive and thistle-like, needing careful spring pruning to manage growth. Remove dead stems for healthy development and enhanced air flow. Use clean tools to avoid disease. Refer to local horticultural resources for specific best practices.

Propagation: Russian knapweed, a resilient perennial weed from the Asteraceae family, is best propagated vegetatively due to its invasive nature. Sowing is seldom advised. Gardeners should isolate new plants and use barriers to manage its rhizomatous growth, ensuring healthy conditions for successful propagation.

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Images of Russian knapweed

Distribution of Russian knapweed

Weed Control

Quickly Identify Russian knapweed

Care Guide for Russian knapweed

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