Gardening covers a wide range of cultivation techniques — ultimately, almost everything other than the specific, intensive techniques of agriculture that generally focus on early succession species, from less intensive techniques even to intensive ones that focus on later succession species.
In a very real way, everything gardens, human and otherwise. Even the most committed hunter-gatherer bands toss a few seeds in areas that they frequent. Villages often define themselves in terms of their preferred gardening techniques, though, such as extensively-managed forest gardens. Much of the jungles that cover the Fifth World consist of cultivated and actively managed ecosystems. Collectively, the people of the Fifth World have effectively terraformed the earth.