Immaculately groomed gardens are usually the domains of meticulous and extremely punctual folk. If you're visiting by appointment, don't be late.
Gardens featuring ornamental grasses, astelias, manicured pebble mulches and modern sculptures are almost always owned by people who don't have much creativity but are desperate for others to think they do, so they've hired a professional to design and create a garden like the Joneses'. Don't fart in their garden, because they wouldn't even do so themselves.
Colourful gardens with heaps of flowering plants signify happy, friendly individuals who are usually at peace with themselves and with the world. Nice people to spend time with.
Unkempt, overgrown gardens can sometimes indicate unfortunate occupants who are not well enough or strong enough to keep their surroundings tidy and don't have the means of paying someone else to do so. In other cases they lack respect for themselves and their neighbours and they are downright lazy.
Quirky and original gardens are owned by creative people, usually with a sense of humour and the balls to be themselves.