St Joseph's Lilies were introduced as an ornamental from Taiwan.

St Joseph’s lilies (Lilium formosanum) are classified as a category 3 invader : ornamentally used plants, may no longer be planted, steps to be taken to prevent  the spreading thereof, particularly in the flood line of water courses and wetlands.

According to the South African alien weeds and invasive plants expert L. Henderson (2001) they are a competitive weed and known to invade grasslands, moist sites, roadsides, plantations.  They are seen as a serious contributor to the degradation of the Grassland Biome.

This is of particular concern regards the Haenertsburg grassland which is critically endangered (less than 5% of the original area still exist) and is now protected. 

An environmental management plan (which also dealt with the removal of alien invasive plants) was drawn up for the Haenertsburg afromontane grassland in 2005, and signed by various stake holders such as the Haenertsburg Environmental Monitoring and Action Group (predecessor of the Friends of the Haenertsburg Grasslands), the Haenertsburg Development Foundation, Greater Tzaneen Municipality, Haenertsburg Rate Payer’s Association, Lepelle Northern Water and adjacent land owners.

Therefore the control of L. formosanum in the Haenertsburg grassland is widely supported.

Tourists can still admire and congregations can still pick the lilies along the roads and in plantations.

Go to SANBI: Declared weeds and invader plants website for a list of declared invaders

http://www.plantzafrica.com/miscell/aliens4.htm