LAUSR

The invasion of Opuntioideae (cacti) was assessed at national, European, and global levels >14 years ago and requires an urgent update. At present, only three species of this subfamily are retained in the official list of the Swiss Federal Bureau of Environment, two of them being potentially invasive. About 550 new observations of Opuntia Mill. and Cylindropuntia (Engelm.) F. M. Knuth in the Swiss Cantons Valais, Vaud, and Ticino have been entered in the Swiss Info Flora database. Our observations include the revision of previously registered and new stations, using a revised taxonomy presented here. Our study covering the last 5 years reveals 12 species, each with a specific ecology. Four species have an invasive potential at a local level in the xeric Central Valais. We characterized the habitat of each species by bedrock and soil type, exposure, and microclimate. Opuntia mesacantha (ex O. humifusa Complex) and O. phaeacantha are currently invasive in the municipality of Sion. Opuntia cymochila (hitherto lumped with O. phaeacantha) is dominant in the municipality of Fully, and Opuntia engelmannii is expanding east of Fully. In Ticino and the Jura foothills, adaptations to 2–3-fold annual precipitation and limestone bedrock are explained by the different soil properties and root systems of Opuntias. Methods of control, in particular, the uprooting currently practiced in Fully and Sion, are discussed.