Question: I recall that an old friend used to deter moles from her garden by planting something around the perimeter. Do you have any idea what this plant was, and does it work?

Answer: There is an old-fashioned annual plant that is sometimes called mole plant or gopher purge. The Latin name is Euphorbia lathyris. This plant exudes an irritating sap and was said to repel moles if simply planted at regular intervals around the garden. Castor-oil plants (Ricinus communis) bear beans that are extremely toxic -- this includes being toxic to people. Castor oil is made from these beans and is often suggested as a repellent for moles -- the extremely toxic component has been removed from the oil. Some companies now sell castor oil-based sprays for the purpose of repelling moles. To be on the safe side, avoid planting castor-oil plants (also called castor beans) and never allow existing plants to flower and fruit.