He acknowledged he and a mate, Darryl Ireland, had also painted park benches in the central town area while Mr Howard's father Graham, a Buller District councillor, re-stained some timber park benches.
"We'd like to have the place look as good as possible, and it's really nice to be active rather than sit at the office desk all the time..." the mayor said.
"We like to take a bit of pride in the place and, as I say, it's just nice to get out and do something."
Shovelling soil into the high school's pop-up garden containers and planting them was no chore for his wife, who loved gardening, her husband said.
Charles, also a keen gardener, will drive past another pop-up garden being installed by council-owned company, WestReef Services, on the main street.
If he fancies, the prince can chill out there in a limestone seat, made by Tai Poutini Polytechnic.
The seat is due in Westport tomorrow.
"It's a big couch - it's got sort of two couch ends then it's got slats in between of rimu timber," Mr Howard said.
The prince may not notice, but a Nelson firm has also steam-cleaned Westport's main street footpaths at a cost of several thousand dollars.
The work was overdue and it was timely to get it done before Charles' visit, Mr Howard said.
He noted that Westport Airport had looked spectacular for the last royal visit, by the Queen - who never actually ventured into Westport - in 1953.
"I do think it is good for a town to be able to put itself forward in a good light," Mr Howard said.
"It doesn't have to cost the earth. If you want to get it all together from various voluntary efforts, it's good."
Mr Howard admitted he could face a bit of an identity crisis when he meets Charles on Saturday.
Westport has become the capital of the fictional South Pacific country,
Becara, for the month-long military exercise and Mr Howard is playing the role of Becara president, Walter Kiaheri.
He said he would meet Charles at Westport Airport as President Kiaheri, then revert to Buller's mayor after the five-minute drive into Westport.
-Westport News