Castor oil is said to work, at least for a while, on both moles and gophers. Moles only eat insects, not plants, so they wouldn’t have eaten the treated grass.

Homeowner only wanted to drive away the gophers and moles, but worries that the castor oil might have killed them, along with some ground squirrels.

Garden centers sometimes sell dedicated gopher repellent sprays, but fish emulsion, blood meal, castor oil, hot peppers, and predator urine may also help repel gophers.

The spikes send out electronic pulses through the ground that will deter moles. One option: Solar Powered 6-Pack Mole Repellent Ultrasonic for Vole, Snakes, Gopher (Buy from Amazon, $32.99).

Homeowner only wanted to drive away the gophers and moles, but worries that the castor oil might have killed them, along with some ground squirrels.