How long should you wait after having a discectomy until you can begin to play golf again?

Depends. In general people can resume most activities almost immediately. I usually tell people to limit heavy lifting, bending, twisting for about a month to let the soft tissues (skin, muscle) heal. Ask your surgeon for specific restrictions; if there was a large hole in the outer disk, more time for healing may be needed.
For a lumbar . Procedure it would ideally be at least 12 weeks after surgery assuming no residual pain symptoms.