English Ivy (Hedera helix): Native to the UK, this is highly invasive in North America, where it climbs and smothers trees, disrupts native groundcover, and is difficult to eradicate.
Sea Buckthorn (Hippophae rhamnoides): While native to some British sand dunes, it is highly invasive in other coastal areas of the UK and beyond, altering soil nutrients and shading out native plants.
Rose of Sharon (Hypericum calycinum): Native to southeast Europe/southwest Asia but widely naturalized and considered a ground-cover "thug" in UK gardens, it has become invasive in various temperate regions, including parts of Australia.
Common Ragwort (Senecio jacobaea): Native to the UK, it has become a serious invasive weed in other countries like Australia, New Zealand, and parts of North America, where it is toxic to livestock.
Sycamore (Acer pseudoplatanus): Native to Europe, it is fully naturalized and often considered invasive in the UK, but also behaves invasively in other regions where it dominates, such as parts of New Zealand and the USA, suppressing native species.
Brambles/Blackberries (Rubus fruticosus): While native, they are aggressive invaders in several parts of the world, particularly Australia, where they are listed as a Weed of National Significance due to their ability to form impenetrable thickets.
Note on "Native" vs. "Naturalized" Invasive Species:
Many of the plants considered "invasive" in the UK (like Japanese Knotweed or Himalayan Balsam) are actually non-native, but they are often mistaken for native due to their prevalence. Conversely, plants that are truly native to the UK can become problematic "garden thugs" that, when introduced elsewhere, often exhibit the same invasive characteristics as foreign plants.