BY BOB SOUVESTRE
October 17, 2012
Perennials are plants that live for three or more years and often require two or more years from seed to flower. Allen Owings, LSU AgCenter horticulturist, says that 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 day lilies, 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 do 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, day lilies, 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.
Replanting day lilies
Late summer and early fall are ideal times to lift, divide and replant day lilies. By preparing now, you will be rewarded with a spectacular show of color next year.
The objective is to help the newly divided plants establish good root systems during the fall and late winter. The transplanting process is relatively easy.
Just divide the plant into several clumps of foliage and roots and retain as many of the roots as possible with each division. Before replanting the division, cut back the foliage to one-third of its original height.
Day lilies are very sensitive to proper soil preparation. Loosen the soil and amend it with organic matter, like pine bark mulch or compost. Follow soil test results and lime if the soil pH is low. Then add a light application of fertilizer when you plant the new divisions. A heaping teaspoonful per plant is adequate.
Blend all amendments with the soil thoroughly.
Day lilies should not be planted too deeply. Plant the new divisions at the same depth as the original plant.
A safe rule of thumb is to set the new division so that the point where roots and foliage meet is no deeper than 1 inch below the surface of the soil. Planting at the proper depth is important for maintaining vigorous day lilies.
Many other perennials can be divided and transplanted using the same steps. These include agapanthus or Lily of the Nile, liriope, amaryllis, ginger and iris.
Also, like day lilies, these perennials need to be planted, or transplanted, in the fall to ensure that they will thrive in the spring.
The East Baton Rouge Parish Master Gardeners are offering a Basic Gardening Series session from 6:30 p.m. to 8:30 p.m. Thursday at the East Baton Rouge Parish Jones Creek Regional Branch Library. To register for the free program, call (225) 756-1150.
The research-based educational program will include two topics: “Soil and Bed Preparation” — Winter is the time to get outside and get your flower beds ready for the upcoming seasonal displays. Learn how to create a flower or garden bed and prepare the soil to accept seeds or transplants.
“Growing Roses” — A mystery to most, growing roses is easier than you might think. Learn the basics and finer points of growing them.
Got a gardening question? Write to Bob Souvestre, horticulturist with the LSU AgCenter, at Burden Center, 4560 Essen Lane, Baton Rouge, LA 70809, or email to firstname.lastname@example.org, or call Master Gardeners at (225) 763-3990.