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Selecting Perennial Plants for the Garden

By Laura Pottorff, Colorado State University Cooperative Extension agent, horticulture and plant pathology

If you are looking for a flower garden that will be a long-term investment in your home landscape, you'll want to consider planting perennials -- flowering plants that bloom year after year.

Unlike annuals -- the bedding plants that you will begin to see from now on in garden centers and other stores -- perennials do not die out each winter. They last through the year and send out new and stronger stalks and foliage each spring.

In most cases, it's easy to tell the difference between annuals and perennials, but not always. So the first thing you'll need to do is be sure of what you are buying. Cost is one clue. The initial cost is greater for perennials, but the plants are a permanent addition to the garden. In the long run, they may be less expensive than buying annuals each year.

You can plant tall perennials at the back of a border and shorter plants in front. With a little planning, it is possible to plant masses of successively blooming flowers for an all-season display. After three years, most perennials need dividing, giving you and your friends hundreds of new plants.

  • Prepare the soil well before you plant. This is the most important phase in producing a perennial garden. Colorado soils can be heavy clay or very sandy. The structure of either soil type can be changed by adding organic matter such as Canadian sphagnum peat moss, well-rotted manure or garden compost. Spread two to three inches of the organic matter over the soil and rototill or double-spade it in. Add a well-balanced fertilizer at this time. Don't take short cuts with soil preparation. When planting a perennial garden, you have just one chance to do it correctly. Once the plants begin to spread their roots, soil amendment becomes a difficult matter, indeed.

  • Select plants that are suitable to the selected site. Most garden centers will display information listing the specific exposure, soil and cultural requirements for each plant. In the absence of signs with this information, read the tag on each variety. Note the amount of sun the plants will receive. Is wind a factor? Many tall flowers do not tolerate wind and snap easily; other tall varieties bend with the wind and perform beautifully. Wind can damage shorter plants too.

Here are some planting hints for perennials.

  • As a general rule, don't plant perennials deeper than they were in the pot.

  • Firm the soil lightly around the plants and water thoroughly with a soft spray nozzle attached to a hose.

  • Protect newly planted perennials from wind for a day or two.

Established perennials may need to be divided every three or four years to maintain vigor. Perennials that bloom in the spring and early summer (peonies and poppies) usually are divided in the fall or when foliage dies. Medium to late summer and fall flowering types (chrysanthemum and aster) should be divided in early spring before growth begins. Iris and day lilies usually are divided immediately after flowering.

Photograph courtesy of Judy Sedbrook.

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Date last revised: 01/05/2010