Family: Linaceae

Origin, Description & Uses
Linum usitatissimum, commonly known as flax, is an annual flowering plant native to a region extending from Türkiye to Iran. It has been cultivated by people for thousands of years and is valued for both its fiber and seeds. Flax typically grows upright with slender stems, narrow leaves, and delicate blue flowers. The plant is widely grown for the production of linen fiber, while its seeds—known as flaxseed or linseed—are used in foods, nutritional supplements, oils, cosmetics, and livestock feed. Because of its long history of cultivation and multiple uses, flax is sometimes planted in gardens, agricultural settings, and educational displays.

Risks & Threats
Although Linum usitatissimum is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that raise concerns for tropical island ecosystems. The species readily produces large numbers of seeds and has the ability to persist in disturbed environments. In regions outside its native range, cultivated flax can occasionally escape cultivation and establish in unmanaged areas. Species with broad environmental tolerance and a history of widespread human cultivation may increase the risk of accidental spread into sensitive habitats. If introduced into suitable environments, flax could potentially compete with native vegetation and contribute to ecological disruption. Because Hawaiʻi’s ecosystems are especially vulnerable to invasive species, Plant Pono recommends choosing low-risk or native plant alternatives whenever possible.

High Risk Traits:

• Naturalized beyond native range
  
• Agricultural weed (volunteers compete with crops)
  
• Congeneric weed (Linum trigynum is a serious weed)
  
• Toxic to animals (cyanogenic glycosides)
  
• Hybridizes naturally with wild relatives
  
• Self-compatible (self-pollinating)
  
• Annual life cycle (rapid generation time)
  
• Intentionally spread by people (cultivation/trade)
  
• Propagules contaminate birdseed
  
• Prolific seed production (>1800 seeds/m²)
  
• Tolerates grazing, herbicides, drought

Low Risk Traits:

• No spines, thorns, or burrs
  
• Palatable to grazing animals
  
• Not shade tolerant
  
• Narrow soil tolerance
  
• No vegetative reproduction
  
• No wind, bird, or external animal dispersal
  
• No persistent seed bank (<1 year)
  
• Low risk of unintentional dispersal