Gardening Q&A: Your mystery plant is a member of the euphorbia genus known as the caper spurge, the mole plant, or more properly as Euphorbia lathyris. Fionnuala Fallon. Sat Sept 09 2023 - 05:00.

He told me that when working around my Euphorbia, ... There is, however, one Euphorbia I would never plant. Despite its reputation, the mole plant (Euphorbia lathyris) doesn’t repel moles.

The weed is caper spurge, Euphorbia lathyris, a native of southern Europe, northern Africa and parts of Asia. Every part of it is poisonous and its milky sap causes allergic reactions.