Flowering Perennials for Georgia Gardens Prepared by Paul A. Thomas, Extension Horticulturist Plants are classed according to their growth cycle as Some sources have suggested that perennials are not annuals, biennials or perennials. Annuals are short-lived well suited to the Southeast. This simply is not true. Many plants that complete their entire life cycle within one perennials perform exceedingly well in Georgia and the growing season. Biennials normally do not bloom until the Southeast in general. Not all perennials perform well here, second season, form seeds and then die. Perennials live but then not all perennials perform well in the Northeast from year to year, with varying bloom times. or even in England. Remember, much of the existing Perennials are also classed as woody (trees and shrubs literature regarding perennials is based on conditions that produce woody above-ground stems and branches that where cooler summer climates prevail. So exercise care in live from year to year) or herbaceous (plants that produce choosing plants well adapted for your particular area. comparatively soft tissues which often die back to ground Most perennials are completely winter hardy, although level at the end of the growing season). Herbaceous there are a few so-called tender perennials that are some- perennials persist by means of various underground times injured by low temperatures. The limiting factors in storage structures—bulbs, corms, tubers, tuberous stems, perennial adaptability in the Southeast are often heat toler- tuberous roots and crowns. ance and diseases that prevail in hot, humid climates. The distinction between annuals and perennials, woody and herbaceous, is not always sharply defined because climate influences growth potential. Further, those SELECTION In addition to climatic adaptation, perennials should be biennials and perennials that bloom the first year along selected based on their ability to perform well and con- with tender perennials (those actually killed by frost) are tribute to specific landscape needs. Height, spread, color, often treated as annuals in the landscape. time and length of bloom, and plant habit should be given This publication is devoted specifically to herbaceous careful consideration. Some perennials are tolerant of poor perennials (subsequently referred to simply as perennials), drainage, others totally intolerant. Sun and shade tolerance primarily to those that persist from crowns and/or fleshy varies. All these factors are important in selecting and us- roots. For information on bulbous-type herbaceous ing perennials correctly. perennials (daffodil, canna, dahlia, etc.), refer to Extension In most cases, a given species has many varieties avail- bulletin 918, Flowering Bulbs for Georgia Gardens. able, which greatly extends the size and/or color range of the species. Commercial catalogs are a good source of USE information on varieties. Purchasing plants by botanical There has been a resurgence of interest in perennials. name and variety is a good idea because common names Home gardeners are becoming more aware of perennials vary from region to region. and so are commercial landscapers. Because perennials live from year to year, they offer a BED PREPARATION certain permanency to the landscape. They are virtually Good bed preparation is extremely important for perenni- unequaled in providing year-round color and interest; als. Remember that you are making a long-term planting; it variations in colors, sizes, habits and time of bloom is much easier and much less disruptive to improve the soil are almost endless. Although many gardens and garden and correct drainage problems before planting. borders feature perennials exclusively—the classic English Beds should be deeply spaded, to a depth of at least 8 perennial border is legend—most often their best use to 10 inches if possible. Many perennials are deep-rooted. comes in the skillful combination with other plants in the Some perennials grow well in sandy soils, but most prefer total landscape. soils higher in organic matter and with better water-hold- also tend to prevent soil crusting, which retards water ing capacity. Heavy clay soils should be amended with penetration, and prevent soil from splashing on lower sand, perlite or coarse bark to improve drainage. Good leaves and flowers. Mulches also provide an added degree drainage is critical to the success of many perennials. To of winter protection. A word of caution: Heavy mulches test for drainage, dig a hole about 10 inches deep and fill that hold moisture can be detrimental, particularly to plants with water. The next day, fill the hole again and see how subject to crown rot. Pine bark, pine straw, wood chips and long the water remains in the hole; if it drains away in a variety of other materials are used successfully. eight to 10 hours or less, drainage is satisfactory for most Maintenance fertilization is essential to the continued perennials. In some situations, it may be necessary to in- growth of perennials. An application of 8-8-8 or 10-10-10 stall under ground drainage lines or construct raised beds. (1.5 pounds per 100 square feet) should be applied in early Have the soil tested. A pH of 6.0 to 6.5 is optimal for spring and once or twice again during the growing season. most perennials. Most Georgia soils are acid and require Maintenance fertilization practices should be based on soil the addition of lime to correct pH. In the absence of a soil tests; application of phosphorus is frequently unnecessary test, add a complete fertilizer such as 8-8-8 or 10-10-10 at once adequate soil levels become established. Water the the rate of a 1.5 pounds per 100 square feet. Incorporate bed after application so that the fertilizer enters the soil the fertilizer and lime, and rake the soil surface smooth. and is available to the plant. Wash any fertilizer off the foliage to prevent fertilizer burn. PLANTING A well-prepared bed requires little cultivation. Deep Many perennials can be seed propagated, but most home cultivation is likely to injure roots and often uncovers gardeners prefer to start with established plants. Most weed seeds, which can then germinate. Weed control perennials can be planted in fall or early spring. Many should usually be done by hand weeding or with the use perennials are now produced in containers, which aid in of herbicides. Exercise extreme caution when using a transplanting and establishment, but many are still field herbicide. Very few are suitable for use around perennials. grown and shipped bare root and dormant. Fall planting is Read the label carefully to be sure it will not injure often better because it gives the plant more time to become desirable plants. established before the start of active growth. Many perennials are top heavy and require support to Unless instructed otherwise, position the crown of the prevent them from bending or falling over during wind and plant at or just below the soil surface. Planting depth is rain. A number of methods can be used to lend support, but critical; if the crown is planted too deeply, it may develop simple wire, plastic or bamboo stakes are often the easi- crown rot. Untangle and spread the roots. Fill the planting est. Done correctly, the plants grow to cover the stakes so hole with soil, gently firm it around the roots and water that they need not detract from the appearance of the plant. thoroughly. You may want to mark or protect the plants, Be careful not to twist the ties too tightly because girdling since when dormant they may be forgotten or stepped on may result. accidentally. CARE AND MAINTENANCE It is a misconception that because perennials last from year to year they require little maintenance and care. While some perennials survive with little care, more require some attention to look their best. In many cases perennial beds require more work than annual beds, which can be com- pletely renovated rather easily each year. But the rewards of perennials make the added maintenance worthwhile. Figure 1. Tie the plant securely to the stake but not so Perennials vary in their drought tolerance, but more tight as to cause girdling. require an ample moisture supply at least during periods of active growth. Do not rely on normal rainfall; irrigate if To maintain vigorous growth, remove mature flowers; necessary. Allow the water to penetrate deeply. Frequent, do not allow seeds to form. Removal will often stimulate light waterings are not advisable because they wet only growth of side shoots on which additional flowers the upper soil depths and result in shallow root growth and will form. Remove dead foliage and stems in the fall. wet foliage and flowers, an invitation to many diseases. Remember that it is natural for the tops of many perennials Soaker hoses and drip irrigation systems work well with to be killed to the ground by frost. Some herbaceous perennials. perennials have evergreen foliage. Mulching helps conserve moisture, control weeds and improve the overall appearance of the garden. Mulches UGA Extension Bulletin 977 • Flowering Perennials for Georgia Gardens 2 DIVISION AND PROPAGATION have special requirements, often a need for chilling, before While the length of time varies, most perennials eventually germination can occur. Be sure you know these specific become overcrowded and require division. Mature clumps requirements before attempting to propagate perennials. can be cut or pulled apart. Divisions should usually contain three to five shoots or growing points. Discard any weak DISEASE AND INSECTS or diseased divisions. The time to divide perennials varies No plant is completely immune to insects and diseases; somewhat, but is most often fall or early spring, coinciding perennials are no exception. A wide spectrum of insects with desired planting dates. Many perennials are easily and diseases can attack perennials and may require control propagated in this way.