A perennial garden is an aggregate entity, not a discrete collection of plants. There is a surprising amount of interdependency that needs to develop between the neighboring plants, an adjustment that takes years and happens mostly underground.

By the time a perennial garden gets fully established, its roots are so interconnected it gets difficult to remove a plant without affecting the entire flower bed. Its residents jointly rely on the nutrients some of the plants release into the soil, on the shade some other plants cast to protect the moisture of the whole border, and on an entire host of worms, insects and anaerobic bacteria which find safe haven inside their intertwined root systems.
Unlike an annual planting, which can be designed to the gardener’s whim, a perennial garden places restrictions on what can or can’t belong in it. There are plant incompatibilities, crowding issues, divergent watering needs, staggered blooming times, territorial dominance, all of which the plants have to resolve among themselves, and over which the gardener has very little say after the fact. The perennial garden is never the same, it changes its colors and patterns from one week to the next, from one year to the next. It has moods, theme colors, favorites. One year the irises run the show, the next year is all about hostas.

Perennial gardens are planted to last decades, even centuries in some cases, so don’t expect them to behave the same as the cheerful annual borders. Most perennials don’t bloom for at least a couple of years as they get established, others take six to ten years to reach maturity. Through that trying time they look like a lost cause, as if they are intent on bring you to despair while you toil and drip sweat over them in vain, and then all of a sudden everything comes together, when you least expect it, in ways you find difficult to believe.

Author's Bio: 

Main Areas: Garden Writing; Sustainable Gardening; Homegrown Harvest
Published Books: “Terra Two”; “Generations”; "The Plant - A Steampunk Story"; "Letters to Lelia"; "Fair"; "Door Number Eight"; "A Year and A Day"; "Möbius' Code"
Career Focus: Author; Consummate Gardener;
Affiliation: All Year Garden; The Weekly Gardener; Francis Rosenfeld's Blog

I started blogging in 2010, to share the joy of growing all things green and the beauty of the garden through the seasons. Two garden blogs were born: allyeargarden.com and theweeklygardener.com, a periodical that followed it one year later. I wanted to assemble an informal compendium of the things I learned from my grandfather, wonderful books, educational websites, and my own experience, in the hope that other people might use it in their own gardening practice.