I wonder a bit how it is that until last Friday, the 20th, I had never heard of Alfred Austin or his book, The Garden that I Love. How did my garden designer decide on that book to leave for me? I've enjoyed it immensely. It's the kind of book you can pick up and read cover to cover and along the way, fall in love with gardening all over again.
Plus, there is some useful information on how to garden, buried in the story. Useful information like how to space out the plants in a garden.
In his own words...
"A garden is not a collection of curios. It is for the most vigorous, the most lovely, and the most fragrant flowers that room should be found; and many these demand for the full display of their charms that the atmosphere should be seen all round them, and that they should not be too much elbowed by their neighbours. It is, perhaps, a little incautious to say this for it may be pressed into the defense of those terrible villa borders where every plant is a specimen, is duly staked, and tied and trained and they all stand at stated and goodly intervals from each other. I pray you avoid it. But if you run into the opposite extreme and crowd certain herbaceous plants overmuch, you curtail their growth and their grace and incur the risk of losing them altogether." (The Garden that I Love, Alfred Austin, 1894)
In my words, space plants not too close, but not too far apart.
If you crowd all the plants together, you are likely to lose a plant or two that just can't compete with a closely planted, vigorously growing neighbor. But if you space them out too far then it isn't really a garden, where plants play off one another and sometimes support one another, it's just a row of plants.
I can think of no better advice on how to space plants in a garden.