A great perennial for planting and establishment in late summer through fall is perennial verbena. Here is Lanai Blush White at the LSU AgCenter Hammond Research Station. (Photo by Allen Owings. Click on photo for downloadable image.)

News Release Distributed 09/07/12

Perennials are plants that live for three or more years and often require two or more years from seed to flower. Gardeners are showing renewed interest in herbaceous perennials because they often need less maintenance, less water and fewer pesticides than annual bedding plants.

Perennials are easily used as ground covers, mixed with annuals, grown in containers and as accents or specimen plants. Many perennials are short bloomers and are best mixed with others that bloom at different times or included with other plants as part of an overall design.

Consider the site before selecting your plants. Although many perennials, such as ferns, tolerate heavy shade, most perennial plants require abundant sunshine. 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.

Though most perennials may take a couple of years to flower from seed, many are as easily started as annuals. The quickest way to have blooming plants, however, is by vegetative propagation, such as by dividing old plants or rooting stem cuttings.

Plants produced vegetatively have all of the traits of the original plant. Propagation by division may seem difficult at first, but most gardeners find that dividing crowns and roots and separating bulbs takes little experience and can be mastered quickly. Try dividing monkey grass for experience, then move on to daylilies, and before long you will have the hang of it.

Perennial plants with shallow roots are easily pulled apart by hand. Long, fibrous roots can be pulled apart with a hand fork. Thickly intertwined roots may need more forceful separation or cutting with digging forks. Replant only those segments with strong roots and a few intact leaves or crowns.

In general, it is best to divide perennials during their dormant or "off" season; divide spring bloomers in fall and fall bloomers in spring. Some perennials may need dividing every three or four years or they will slowly crowd themselves into clumps of nonflowering leaves and roots.

Many perennial plants may be propagated from stem cuttings, which does not disturb the plants’ roots. Take stem cuttings during 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, but leave a few leaves to provide a source of energy for root initiation and growth.

You may not think about planting perennials this time of the year, but the success of fall through late-winter planting is good.

Good choices for herbaceous perennials for Louisiana include lantana, perennial verbena, butterfly bush, Mexican heather, coneflower, rudbeckia, perennial salvia, iris, daylilies, Shasta daisy, coreopsis and many more. Be sure to select perennial flowers appropriate for your particular site and growing conditions. Select varieties that have been proven superior in LSU AgCenter trials.

You can see more about work being done in landscape horticulture by viewing the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals.

Rick Bogren