Most of us do not have the time to commit ourselves regularly to our garden, however much we wish we could. We also have conflicting demands on the garden, it is not just something beautiful to contemplate but also a place to live in and enjoy. So, we end up creating an informal garden that suits our lifestyle. It is none the worse for that.
What is an informal garden? An informal garden is everything a formal garden is not. It is a garden designed around our tastes and lifestyle. The borders are full of plants that we like but not necessarily planted with military precision. The lines are not regular but comfortable and enjoyable, a bit like a favorite chair. There are lots of different things to see, but they are not necessarily connected in such a rigid way as in a formal garden.
There is plenty of room for children to play, and no one gets too hysterical is a ball gets into the beds or the shape of a shrub is spoilt by being turned into a camp. The gardener still takes a lot of trouble over how it is planted and how it looks, but the garden carries with it an air of comfortable informality.
What about informal plants? Virtually any plant is suitable for an informal garden, which is the joy of this garden type (this is why no box containing a listing of recommended plants has been given here). It is the way in which plants are used, not the plants themselves, that is the key.
What you could do is you wish is to create different areas for different plants. For example, if you are particularly fond of plants that favor damp conditions, you could make one big area into a bog garden. Similarly, a rock garden or a gravel bed could be introduced for plants that tend to favor drier conditions.
You can also create a more mixed garden, with annuals, perennials, climbers, shrubs and even trees, combined and arranged as you please. You could also experiment with using colors and textures in various creative ways.