1. A weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized
   - lesser knapweed, black knapweed, hardheads

Type of: knapweed

• serger
• serial
• serial killer
• serial monogamy
• serial murderer
• streptobacillus
• streptocarpus
• streptococcal
• streptococcal sore throat
• streptococci
• streptococcic
• streptococcus
• Streptococcus anhemolyticus
• streptococcus mutans
• streptococcus tonsilitis
• streptodornase
• streptokinase
• streptolysin
• streptomyces
• Streptomyces erythreus
• Streptomyces griseus
• Streptomyces scabies
• Streptomycetaceae
• streptomycin
• Streptopelia