Herbaceous perennials offer easy care and beauty to landscape

John Young, Gill, Daniel J., Owings, Allen D.  |  12/18/2008 10:42:47 PM

Chrysanthemums are among the many perennials to choose from to beautify the landscape year after year. (Click to download. Photo by Mark Claesgens.)

Sustainable Landscape News Distributed 12/18/08

By LSU AgCenter Horticulturists

Perennials are plants that live for three years or more and often require two years or more from seed to flower. Technically, trees, shrubs and lawn grasses are all perennials, but gardeners use the term perennial as an abbreviation for “hardy, herbaceous perennial” – a group of nonwoody plants that reliably survive winter cold and grown for their attractive flowers or foliage.

Some perennials are evergreen and never go completely dormant, while others lose their leaves and essentially disappear at certain times of the year, usually winter.

Because they live for years, perennials reduce maintenance in the landscape compared with annuals. Perennial beds do not have to be cleaned out, prepared and replanted twice a year the way annual beds must be handled. Well-established perennials also generally need less watering to get by, particularly those that are drought-tolerant (such as many ornamental grasses, lantana, black-eyed Susan and coneflower).

These enduring plants are being rediscovered by Louisiana gardeners for their dependable seasonal effects. Perennials are easily used as ground covers, mixed with annuals, grown in containers, used as accents or specimen plants and included with other landscape plants as part of an overall design. Because many perennials bloom for a short period (a few weeks), it is best to combine various perennials that bloom at different times to extend the colorful display.

Also, consider the site before selecting your plants. Some perennials grow in virtually any of the growing conditions found in the typical landscape, from full sun to full shade and well-drained to boggy areas. But, you must carefully match the preferred growing conditions for a perennial with the location where you plant it. Air circulation is important for avoiding diseases – stagnant, warm and humid air creates ideal conditions for diseases. Perennial plants also require properly prepared soil, and a few have specific drainage and fertility requirements.

Although most perennials may take a couple of years to flower from seed, many are started as easily started as annuals. The quickest way to have blooming plants, however, is to purchase transplants at local nurseries. Perennials may not look like much when you purchase them. This is a reason newer gardeners, accustomed to buying annuals in full bloom, are slow to appreciate perennials. You must be able to imagine how they will look when they bloom. Pictures on labels, online and in garden references can help with this.

Gardeners also can create new plants from ones they already have by vegetative propagation, such as dividing old plants or rooting stem cuttings. Plants produced vegetatively have all of the traits of the original plant.

To divide perennials, first dig up the entire clump using a shovel or garden fork. Study the clump carefully and note the crowns or shoots present. Decide how many pieces to divide the clump into. Generally, each division should have several crowns or shoots. Decide where to make the cuts so that you avoid cutting through crowns or damaging shoots. Finally, cut apart the clump with a large, sharp knife. Be careful and wear leather gloves.

Perennial plants with shallow roots may be pulled apart by hand. Replant or pot up the divisions immediately. Try dividing monkey grass for experience; then move on to daylilies, and before long, you will have the hang of it.

In general, it is best to divide perennials during their dormant season; divide spring bloomers in the fall or winter and fall bloomers in winter or spring. Some faster-growing perennials may need dividing every two or three years or they will become crowded and bloom less or outgrow their location.

Many perennials may be propagated from stem cuttings. Take stem cuttings during the spring or early summer, choosing stems that are mature and firm but not yet hardened and woody. Cut off 4- to 6-inch segments using a sharp knife or shears and pinch off the succulent tip and any flower buds to force the cuttings to concentrate their energy on producing roots. Remove the lower leaves that will be below the surface of the rooting medium (such as potting soil) but leave a few leaves to provide a source of energy for root initiation and growth.

You may not think about planting perennials in this time of year, but the success of fall- through late-winter planting is good. Recommended herbaceous perennials for Louisiana include lantana, perennial verbena, liriope, Mexican heather, coneflower, cast iron plant, guara, chrysanthemum, yarrow, rudbeckia, perennial salvia, Louisiana iris, daylilies, Shasta daisy and coreopsis among others.

Be sure to select perennial flowers appropriate for your particular site and growing conditions. Whenever possible, select varieties that have proven superior in LSU AgCenter trials. Come to LaHouse in Baton Rouge to see our herbaceous perennial planting efforts and other sustainable landscape practices in action. The home and landscape resource center is located near the intersection of Burbank Drive and Nicholson Drive (La. Highway 30) in Baton Rouge across the street from the new LSU baseball stadium. Go online to www.louisianahouse.org and www.lsuagcenter.com/lyn for more information.

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Contacts:
Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Allen D. Owings at (985) 543-4125 or aowings@agcenter.lsu.edu
John Young at (225) 578-2415 or (225) 578-2222 or JoYoung@agcenter.lsu.edu
Editor: Mark Claesgens at (225) 578-2939 or mclaesgens@agcenter.lsu.edu

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