Spotted Knapweed Centaurea maculosa
Previously known as:
- Centaurea biebersteinii
- Centaurea stoebe ssp micranthos
- Centaurea stoebe ssp stoebe
- Phonetic Spelling
- sen-TAR-ee-ah mak-yoo-LOH-suh
- Description
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Spotted knapweed is an herbaceous biennial or perennial weed in the Asteraceae (aster) family and native to Europe and western Asia. It is considered invasive in many states within the United States, mostly the northwest and north central states. The plant grows on stream banks, pond shorelines, sand prairies, old fields and pastures, roadsides, along railroads, and many open, disturbed areas. It crowds out native species and forage for livestock. The flowers are a vibrant lavender with black margins of the flower bract tips, which give the flower heads a spotted look and is the origin of its common name.
Spotted knapweed prefers to grow in dry, sterile, gravelly or sandy soils, and full sunlight. It usually has a stout taproot below a basal rosette of deeply lobed leaves covered in fine, short hairs. As many as 6 erect stems emerge from the same root crown during a single growing season and grow up to 3 feet tall. The seeds are primarily distributed by the wind. An individual plant may produce as many as 40,000 seeds.
Light infestations of this invasive weed can be managed by pulling the weeds by hand or by mowing early when the plant is just beginning to flower. Plants are less likely to regrow if allowed to form flower stalks before mowing. All management methods must be repeated for several years until seeds stored in the soil become depleted. Spotted knapweed is resistant to some herbicides, likely due to wooly hairs on its stems and leaves limiting retention or penetration of the herbicide.
Insects, Diseases, and Other Plant Problems: Invasive tendencies.
- See this plant in the following landscape:
- Cultivars / Varieties:
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- Tags:
- Cultivars / Varieties:
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- Tags:
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Attributes:
- Genus:
- Centaurea
- Species:
- maculosa
- Family:
- Asteraceae
- Life Cycle:
- Biennial
- Perennial
- Recommended Propagation Strategy:
- Seed
- Country Or Region Of Origin:
- Europe, Western Asia
- Distribution:
- Most every state in the the USA
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Whole Plant Traits:
- Plant Type:
- Weed
- Wildflower
- Habit/Form:
- Erect
- Growth Rate:
- Rapid
- Maintenance:
- High
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Cultural Conditions:
- Light:
- Full sun (6 or more hours of direct sunlight a day)
- Soil Texture:
- Sand
- Shallow Rocky
- Soil pH:
- Acid (<6.0)
- Neutral (6.0-8.0)
- Soil Drainage:
- Occasionally Dry
- Very Dry
- NC Region:
- Coastal
- Mountains
- Piedmont
- USDA Plant Hardiness Zone:
- 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
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Fruit:
- Fruit Color:
- Black
- Gold/Yellow
- Display/Harvest Time:
- Fall
- Fruit Type:
- Achene
- Fruit Length:
- < 1 inch
- Fruit Width:
- < 1 inch
- Fruit Description:
- An achene (about a quarter-inch long) finely hairy, straw-colored at maturity with a tuft of short, stiff, light brown bristles at the tip.
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Flowers:
- Flower Color:
- Purple/Lavender
- Flower Inflorescence:
- Cyme
- Head
- Flower Bloom Time:
- Summer
- Flower Shape:
- Dome
- Flower Petals:
- Bracts
- more than 20 petals/rays
- Flower Size:
- 1-3 inches
- Flower Description:
- Up to 1 in. lavender flower heads with a harsh, prickly, black-tipped bract
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Leaves:
- Leaf Color:
- Gray/Silver
- Green
- Leaf Feel:
- Smooth
- Leaf Type:
- Compound (Pinnately , Bipinnately, Palmately)
- Leaf Arrangement:
- Alternate
- Rosulate
- Leaf Shape:
- Linear
- Leaf Margin:
- Lobed
- Hairs Present:
- Yes
- Leaf Length:
- > 6 inches
- Leaf Description:
- A basal rosette of deeply lobed petiolate leaves approximately 8 inches in size is produced the first year. Pubescent stems form when young with highly dissected leaves that are alternate and may be slightly lobed or linear. Leaves become smaller and less lobed toward the apex.
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Stem:
- Stem Color:
- Gray/Silver
- Green
- Stem Is Aromatic:
- No
- Stem Form:
- Straight
- Stem Surface:
- Hairy (pubescent)
- Stem Description:
- The stem is erect or ascending, slender, hairy and branching, and can grow up to three feet tall. As many as 6 stems emerge from the same root crown during a single growing season.
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Landscape:
- Problems:
- Weedy