Two of the lazy gardener's favorite strategies to achieve the goal of a carefree landscape are to replace as much lawn as possible with gardens and fill them with as many perennials as possible. Designing a perennial landscape is not difficult but it is essential; good stock is more expensive than flats of annuals. Perennials live for years and propagate more plants to fill empty spaces and start new borders; tearing out plants because they are in the wrong place is never cost-effective.
Design your gardens to complement the style and scale of the rest of your landscape. Cottage gardens and formal gardens are each suited to very different sizes and types of properties. Your garden should match your residence and overall landscape but should provide a place to retreat from it, too. Surround it with shrubs, trees or garden walls to establish it as an "outdoor room" on your property.
Establish a color scheme. Monochromatic schemes use shades and hues of one scheme. Complementary schemes use contrasting colors; red-green, purple-yellow and blue-orange in shades of each. An adjacent or analogous scheme uses colors next to each other on the color wheel; yellow-green, red-purple. Use white or complementary colors for contrast to make parts of the garden "pop" to move the eye along.
Utilize form, line and shape to move the eye from back to front and one end to the other. Put tall plants in the back, of course. Plant varieties in "drifts" that undulate through the bed rather than clumps that tend to stop the eye as it moves through the garden. Plan on at least three plants of each variety to avoid a crazy-quilt of too many plants jammed together.
Introduce texture with foliage plants like arum, crotons and hostas. Most perennials need full sun but many need afternoon or dappled shade; introduce moving shade with trees and shrubs. Distinctive flowering plants like daylilies, cranesbill and lilyturf provide focal points as well as texture. Vary placement of accent plants so they don't follow a line but rather appear in waves across the width of the garden.
Provide for a succession of blooms. The garden should have something to see all year. Early, mid- and late-season blooming flowers are easy to organize; you can even alter color schemes as the season progresses. Don't neglect the cooler seasons, though. Plant a Japanese maple for fall color, a redosier dogwood for winter accent or a small evergreen to hold suet holiday feeders for the birds.
Add ornaments and structures that fit the style and scale of your garden. A bench is a must. Water features require space but a pond can be tucked in a quiet corner. Add lanterns for garden dinners or containers for tender plants that will live indoors in the winter. Walks replace more lawn.