Family: Malvaceae

Origin, Description & Uses
Sida spinosa, commonly known as prickly mallow, prickly sida, or spiny sida, is a small, upright herb or subshrub native to tropical and subtropical regions around the world. It typically grows 1–3 feet (0.3–1 m) tall and is recognized by its yellow flowers, heart-shaped leaves, and small spines that develop near the leaf bases and seed capsules. The species thrives in disturbed areas, roadsides, agricultural lands, pastures, and waste places. In some regions it has been used in traditional medicine, while its fibrous stems have occasionally been utilized for cordage and other minor purposes.

Risks & Threats
Sida spinosa is naturalized throughout the Hawaiian Islands, including Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island, and has been present in Hawaiʻi since at least the 1800s. This species possesses traits that are cause for concern, including prolific seed production, persistence in disturbed habitats, and the ability to spread rapidly in open areas. It can become a troublesome weed in agricultural settings, pastures, roadsides, and natural ecosystems, where it may compete with desirable vegetation and hinder restoration efforts. Because it is naturalized and could detrimentally impact tropical island ecosystems, planting is not recommended. Where suitable, choose a low-risk or native alternative instead. Since Sida spinosa is already widespread in Hawaiʻi, landowners and land managers should focus on preventing its introduction into areas where it is not yet abundant and managing existing populations to reduce further spread and ecological impacts.

High Risk Traits:

• Broad climate suitability
  
• Grows in temperate and tropical climates
  
• Naturalized on the Hawaiian Islands of Kauai, Oahu, Lanai, Maui, Molokai and Hawaii. Widely naturalized elsewhere
  
• A weed of crops, pastures, roadsides, disturbed sites and waste areas
  
• Other Sida species are invasive weeds
  
• May be unpalatable to animals (although some limited browsing may occur)
  
• Shade tolerant
  
• Reproduces by seeds
  
• Self-compatible
  
• An annual, reaching maturity in one growing season
  
• Seeds dispersed externally by adhering to animals and people. Seeds also dispersed as a produce contaminant
  
• May produce prolific numbers of seeds in certain situations
  
• Forms a persistent seed bank (3+ years for a small percentage of seeds)

Low Risk Traits:

• In the Hawaiian Islands, primarily a weed of disturbed areas and waste lands, and generally not considered a significant environmental weed
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control