Books and gardeners are helpful; but, like other doctors, they differ.

I think one is often slower to learn anything than one need be, from not making at once for first principles.

If one knew more of these, it would be easier to apply one's own experience, and to decide amid conflicting advice.
Here are a few rough-and-ready "first principles" for you.
_Hardy flowers in hedges and ditches are partly fed, and are also covered from cold and heat, and winds, and drought, by fallen leaves and refuse.

Hardy flowers in gardens have all this tidied away from them, and, being left somewhat hungry and naked in proportion, are all the better for an occasional top-dressing and mulching, especially in autumn._ It is not absolutely necessary to turn a flower border upside down and dig it over every year.

It may (for some years at any rate), if you find this more convenient, be treated on the hedge system, and _fed from the top_; thinning big clumps, pulling up weeds, moving and removing in detail.
_Concentrated strength means large blooms._ If a plant is ripening seed, some strength goes to that; if bursting into many blooms, some goes to each of them; if it is trying to hold up against blustering winds, or to thrive on exhausted ground, or to straighten out cramped and clogged roots, these struggles also demand strength.