Family: Plantaginaceae

Origin, Description & Uses:
Linaria purpurea (purple toadflax) is native to central and southern Italy, extending to Sicily. It is a slender, upright perennial herb in the plantain family (Plantaginaceae), typically growing 2–4 feet tall with narrow, gray-green leaves and tall spikes of small, tubular purple to lavender flowers. It is widely cultivated as an ornamental plant for its long bloom period, airy texture, and ability to attract bees and other pollinators. Gardeners often use it in borders, cottage gardens, and naturalistic plantings due to its drought tolerance and easy growth in a range of soils.

Risks & Threats:
In Hawaiʻi, Linaria purpurea is naturalized and has demonstrated the ability to persist outside of cultivation. It can produce large numbers of seeds that spread easily, allowing it to establish in disturbed areas and potentially compete with native vegetation. While it may appear delicate in gardens, it can behave more aggressively in suitable conditions, forming persistent populations that are difficult to manage once established. Because of these traits—high seed production, adaptability, and escape from cultivation—it is considered a species of concern for tropical island ecosystems, where it may contribute to the displacement of native plants and alteration of habitat structure. Choosing a low-risk or native alternative is recommended to help protect Hawaiʻi’s unique ecosystems.

High Risk Traits:

• •Broad climate tolerance
  
• Naturalized in California and Hawai'i Island
  
• Several species in the genus are serious weeds (Linaria dalmatica and L. vulgaris)
  
• Dispersed by humans

Low Risk Traits:

• Not a known invasive elsewhere (not widely introduced)
  
• Unarmed (no spines, thorns, burrs)
  
• Non-toxic
  
• Requires full sun
  
• Not tolerant of a wide variety of soils