Ask Tomasgreen
What is this? The green berries reveal more than you might think
The berry shape and little star at the attachment point are the deciding clues. Bittersweet is often seen at this stage in autumn before its berries turn red.
Reader: @ullisgullis · · 1 min read

This is bittersweet, Solanum dulcamara. The photograph fits well: small rounded berries in hanging clusters, a persistent star-shaped calyx behind each berry and a dark purple-tinged stem.
In September, the berries are commonly still green or ripening; they turn red later. The whole plant is poisonous, especially the berries, so if it grows where children or pets can reach it, removing the fruit or the whole plant is sensible.
Sources and images 1
- Original reader contribution ↗Reader question