Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Square-stalked St. John's-wort, Hypericum tetrapterum, in Peel Region, Ontario: a new non-native vascular plant species for Eastern North America.

Abstract

The Eurasian Square-stalked St. John's-wort (Hypericum tetrapterum Fr.: Hypericaceae) was found growing in an open Eastern White Cedar (Thuja occidentalis L.) swamp in Caledon, Regional Municipality of Peel, Ontario. This is the first record for eastern North America; previous North American occurrences have been on the Pacific coast in Vancouver, British Columbia, Canada (1991), and in Wahkiakum County, Washington State, USA (2003).