Does anyone know anything about gardening?

Hard agree.

100%

From the RHS, who - despite recently beginning to see the light on this - are not shy about pesticide use generally:

Ants should be tolerated in gardens wherever possible, they do not cause direct damage to garden plants and are an important part of the biodiversity gardens can support. They predate many other invertebrates

Ant control with pesticides in gardens is unnecessary, impractical and ineffective. Pesticide use will also potentially harm other non-target animals having a detrimental effect on garden health.

Many proprietary ant powders, baits, sprays and aerosols are available for controlling ants in and near buildings, these are not suitable for garden use or application on plants or soil and can have a detrimental effect