I’m not quite sure how the discussion veered off into workers’ clothing when you’re really asking about a color palette for branding purposes. Employee clothing would vary across seasons and might be high-viz chartreuse or olive-drab green or tan-colored t-shirts with a company patch or a bit of screen printing. It’s something to consider as part of the bigger package, but likely not something to drive the the general color scheme.
As for logos, truck graphics, business cards, promotional brochures and that sort of thing, I’d go back to what @OVOAO originally mentioned about pulling the colors from the subject matter — gardening and gardens.
Vegetation is dominated, of course, by green and landscaping is typically punctuated by the colors of flowers that come in most every color from pastel pinks to bright yellows to dark reds and oranges. One possible direction out of many would be to, in some way, duplicate this palette by using green as the dominant color and using flower colors as secondary accents. Keep in mind there needs to be versions of the logo that don’t have all these colors.
Like I said, this is just one idea of many possible solutions.