Daniel Gill, Merrill, Thomas A. | 1/29/2007 10:53:48 PM
By Dan Gill
LSU AgCenter Horticulturist
When you finally reach the "been there, done that" stage with the cycle of planting annuals, you might consider that perennials offer exciting challenges and great fun.
February is a good time to transplant or divide perennials already in your landscape, and now through April is an excellent time to plant new perennials.
Perennials are plants that live for three or more years. Unlike annuals, perennials do not die after flowering and setting seeds.
Technically, trees, shrubs and lawn grasses all are perennials, but gardeners generally use the term "perennial" as an abbreviation for "hardy, herbaceous perennial" – a group of nonwoody plants that reliably survive winter cold and are grown for their attractive flowers or foliage. Some perennials are evergreen and never go completely dormant, while others loose their leaves and essentially disappear at certain times of the year, usually winter.
Utilizing perennials is not necessarily more difficult than growing annuals, but it is different. Because they will become a part of your garden for a number of years, using them effectively does require learning more about the plants.
Keep in mind when an annual is finished blooming it is pulled out and replaced with something that will continue blooming. When a perennial finishes blooming it is left in place, and other plants in other locations must continue the floral display.
Gardeners frequently move perennials around – trying to find a location where they will look and grow their best or just trying out different combinations. Many times we are unfamiliar with exactly what a perennial will do for us until we have grown it in our own gardens. After a year or two, a gardener may realize that another location for the plant would be better.
If transplanted now, most perennials will barely miss a beat, particularly if you are careful to dig up most of the root system and replant immediately in a new location. If you wait and try to transplant later in the season, warmer weather makes it more likely perennials will suffer increased transplant shock.
Do not transplant perennials currently in active growth at this time, such as Louisiana irises, acanthus, calla lilies and Easter lilies.
Some perennials are best divided every year or two, but most can be left alone for two to three years or even longer. Dividing helps control the size of the plant and the space it occupies, as well as rejuvenating it. Dividing perennials also is a good way to create more plants you can share with friends or plant in other areas of your landscape.
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. Then decide how many pieces to divide the clump into. Generally, each division should have several crowns or shoots. Next, 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 – being sure to be careful and wearing leather gloves to protect yourself.
Once that’s done, replant or pot up the divisions immediately.
Early spring is a good time to plant perennials – although perennials may not look like much when you purchase them this month. That’s one of the reasons newer gardeners, who are 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 in two or three months, or even at the end of the summer, to value them in February.
Plant perennials into well-prepared beds – spacing them according to information on the label, references or local advice. Most perennials will grow considerably larger than the size of the young plant you purchase. Do not crowd them.
Plant with the top of the root ball even with or slightly above the soil of the bed. Many perennials will rot if planted too deeply. If the roots are in a tightly packed mass, pull apart and spread the roots out somewhat when planting. A small amount of slow-release fertilizer also may be placed in the planting hole. Firm the soil around the plant and then water newly planted perennials thoroughly. Mulch the bed to control weeds, but do not cover the perennial plants.
Success with perennials in Louisiana depends largely on proper selection, which begins with a general rejection of perennials that only grow well north of hardiness zone 8. To survive here, perennials must be able to endure the heat, humidity and rain of summer and the diseases that season brings.
Growing conditions for the area where you intend to plant a perennial also should be noted, and you should select perennials that will thrive in those conditions.
Flower colors also are very important. Decide on a color scheme. Select perennials that bloom at various times of the year for extended displays of color.
Heights must be considered, and don’t forget to choose perennials with a variety of textures and growth habits to create interest and contrast in the composition.
For more information and recommendations of perennials that do well in Louisiana, I recommend "Perennial Garden Color" by William Welch and "Perennials for the Coastal South" by Barbara Sullivan.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.