You can plant the herb pennyroyal around the base of the tree to keep ants away.
The Sun
Plant herbs in some pots and shove utensils in others.
Times, Sunday Times
I want to plant herbs on my windowsill.
Times,Sunday Times
Some folks say planting the herb horehound will repel grasshoppers.
Houston Chronicle
Consider planting the herbs in the big olive oil tins that restaurants use.
Times, Sunday Times