Search ads and local service ads are the only type of Google Ads he should be doing. We've run these very successfully for lawn care/gardening companies, and tree surgeons.
This should be based on keyword and customer research; e.g. what services he offers and what keywords a customer would look for if they're interested, plus what geographic area he wants to work in. This will likely be along the lines of "lawn care/treatment/mowing near me", and similar terms for other tree care and gardening work.
He will need a well optimised website, with landing pages relevant to each of the services he advertises for, with a compelling reason to use him, plus a good sign up lead form/process. This needs testing and tweaking to get the best results, plus you need to ensure you can track all leads (form fills/phone calls etc).
For ads to appear in the Google 3 pack/map pack for relevant searches, he will need a Google Business Profile, that's again well set up, with relevant details, images, plus phone & form tracking.