Fact Sheet ST-371October 1994

Magnolia grandiflora

Figure 1. Middle-aged Southern Magnolia.

Southern Magnolia 1

Edward F. Gilman and Dennis G. Watson2

INTRODUCTION

This large, stately, native North Americanevergreen tree with its large, beautiful, saucer-shaped,fragrant flowers is almost a Southern landscapetradition (Fig. 1). It has been selected as the state treeof Mississippi. Capable of growing at a moderate rateto a height of 80 feet or more with a 30 to 40-footspread, Southern Magnolia forms a dense (more openin the shade), dark green pyramidal shape, the lowerbranches often bending to the ground. However, formand growth rate on seedlings is incredibly variable.Some are dense and make great screens, others arevery open with large spaces between branches; somehave a narrow, almost columnar form, others are aswide as they are tall. Select from the many availablecultivars to ensure the desired shape and density. Thetrunk on large specimens can grow to more than threefeet in diameter, and frequently grows straight upthrough the center of the crown. Branches aretypically numerous and small in diameter. Removethose few branches which occasionally form weak,tight crotches.

GENERAL INFORMATION

Scientific name: Magnolia grandifloraPronunciation: mag-NO-lee-uh gran-dih-FLOR-uhCommon name(s): Southern MagnoliaFamily: MagnoliaceaeUSDA hardiness zones: 7 through 10A (Fig. 2)Origin: native to North AmericaUses: espalier; wide tree lawns (>6 feet wide);recommended for buffer strips around parking lots orfor median strip plantings in the highway; screen;

shade tree; specimen; residential street tree; no provenurban toleranceAvailability: generally available in many areas withinits hardiness range

1. This document is adapted from Fact Sheet ST-371, a series of the Environmental Horticulture Department, Florida Cooperative Extension Service,Institute of Food and Agricultural Sciences, University of Florida. Publication date: October 1994.

2. Edward F. Gilman, associate professor, Environmental Horticulture Department; Dennis G. Watson, associate professor, Agricultural EngineeringDepartment, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.

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DESCRIPTION

Figure 2. Shaded area represents potential planting range.

Height: 60 to 80 feetSpread: 30 to 40 feetCrown uniformity: irregular outline or silhouetteCrown shape: oval; pyramidalCrown density: moderateGrowth rate: mediumTexture: coarse

Foliage

Leaf arrangement: alternate (Fig. 3)Leaf type: simpleLeaf margin: entireLeaf shape: elliptic (oval); ovateLeaf venation: banchidodrome; pinnateLeaf type and persistence: broadleaf evergreen;evergreenLeaf blade length: 8 to 12 inches; 4 to 8 inchesLeaf color: greenFall color: no fall color changeFall characteristic: not showy

Flower

Flower color: whiteFlower characteristics: pleasant fragrance; springflowering; summer flowering; very showy

Fruit

Fruit shape: elongatedFruit length: 3 to 6 inches; 1 to 3 inchesFruit covering: dry or hardFruit color: brown; redFruit characteristics: attracts birds; fruit, twigs, orfoliage cause significant litter; showy

Trunk and Branches

Trunk/bark/branches: bark is thin and easilydamaged from mechanical impact; droop as the treegrows, and will require pruning for vehicular orpedestrian clearance beneath the canopy; notparticularly showy; should be grown with a singleleader; no thornsPruning requirement: needs little pruning to developa strong structure

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Breakage: resistant

Figure 3. Foliage of Southern Magnolia.

Current year twig color: greenCurrent year twig thickness: thickWood specific gravity: 0.50

Culture

Light requirement: tree grows in part shade/part sun;tree grows in full sunSoil tolerances: clay; loam; sand; slightly alkaline;acidic; extended flooding; well-drainedDrought tolerance: moderateAerosol salt tolerance: moderateSoil salt tolerance: good

Other

Roots: surface roots are usually not a problemWinter interest: no special winter interestOutstanding tree: not particularly outstandingInvasive potential: little, if any, potential at this timeOzone sensitivity: tolerantVerticillium wilt susceptibility: susceptiblePest resistance: long-term health usually notaffected by pests

USE AND MANAGEMENT

The five to 8-inch-long, leathery, oblong, shinyleaves are shed as new foliage emerges but the debrisis well-hidden by the dense foliage of the lower limbs,if they are left on the tree. But some people considerthis a litter nuisance when the large, slowly-decomposing leaves drop on the sidewalk, lawn or

patio. The underside of the leaves is covered with afine, red-brown fuzz which is more prominent on someselections than others. In late spring and sporadicallythroughout the summer, huge, 8-inch-diameter, waxy,fragrant, white blossoms open to perfume the entiregarden. Fuzzy brown cones follow these blooms,ripening in fall and winter to reveal bright red seedswhich are used by a variety of wildlife.

Long-used as a striking garden specimen, SouthernMagnolia can also serve as a dense screen (select oneof the dense cultivars), windbreak or street tree (withlower limbs removed). The only objection to this treeas a street tree might be the falling leaves and fruit.Its ease of growth and carefree nature make SouthernMagnolia ideal for the low-maintenance landscape.With proper pruning, Southern Magnolia trees can alsobe used as an interesting espalier.

If moist, peaty soils are available, SouthernMagnolia will thrive in full sun and hot conditionsonce established. If irrigation cannot be providedperiodically, plants located in partial shade for severalyears after planting seem to grow better. Very droughttolerant when grown in areas with plenty of soil forroot expansion. Only moderately drought tolerant inrestricted-soil areas or in areas with poor, dry soil.Southern Magnolia prefers acid soil but will tolerate aslightly basic, even wet or clay soil. It is generally toohot and dry in central and western Texas andOklahoma, and the soil pH is often too alkaline forthis tree. The root system is wider spreading thanmost other trees, extending from the trunk a distanceequal to about four times the canopy width. Thismakes it very difficult to save existing Magnolia treeson construction sites. Be sure that there are no rootscircling close to the trunk, as Magnolia is prone togirdling roots. Cut any circling roots prior to planting.Field-grown trees recover slowly from transplantingdue to the wide-spreading root system in the nursery,and trees often transplant best in winter and spring, notin the fall.

The species germinated from seed is quite variablein growth rate and form with some trees dense andcompact, others loose and open. A number ofcultivars are available: ‘Bracken’s Brown Beauty’ hasan unusually dark brown lower leaf surface and isconsidered one of the best selections; ‘Cairo’ has anearly and long flowering period; ‘Charles Dickens’ hasbroad, nearly blunt leaves, large flowers and large redfruit; ‘Edith Bogue’ is the hardiest of the cultivars andwill bloom when only two to three-years-old; ‘Glen St.Mary’ has a compact form, will bloom when young, is

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slow-growing, and the leaves have a bronze underside;‘Gloriosa’ has large flowers and leaves; ‘Goliath’ hasflowers up to 12 inches across, a long bloomingperiod, and a bushy habit of growth; ‘Hasse’ can beused for a compact, dense hedge or screen;‘Lanceolata’ has a narrow pyramidal form, narrowerleaves with rusty undersides; ‘Little Gem’ has a dwarfupright form, probably to 30 feet tall, small leaves andflowers, is very slow-growing, flowers heavily at anearly age and for a long time during the summer (5-months), and has bronze leaf-undersides. It will bloomwhen only three to four feet tall and is excellent as apruned evergreen hedge, for use as a small street treeor for use as an espalier; ‘Majestic Beauty’ (patented)has large, dark green leaves, a pyramidal shape, andprofuse flowering; ‘Praecox Fastigiata’ has upright,narrow growth habit; ‘Samuel Sommer’ has an upright,rapid growth habit and flowers up to 14 inches across;‘Victoria’ is very hardy, has small flowers, and rust-red leaf-undersides. There are others, but it is oftendifficult to see real differences among them.

Two of the most recommended Magnolias are:Magnolia x ‘Galaxy’ and ‘Spectrum’ from U.S.National Arboretum; both have excellent trunks andsuperior flowers.

Propagation is by cuttings (for the cultivars),grafting, or seed.

Pests

Scales of various types will infest twigs andleaves. Magnolia scale is the most common scale andcan be one half-inch-across. Overwintering scales canbe controlled with horticultural oil. Trees appear togrow fine even with heavy infestations, although theycan be unsightly.

Tulip-poplar weevil (sassafras weevil) feeds as aleaf miner when young and chews holes in the leavesas an adult.

Magnolia borer is a problem on young nurserystock. It girdles the trunk usually just below the soilsurface. Control is difficult but attainable with theproper material.

Diseases

Magnolia may be subject to leaf spots, blights,scabs and black mildews caused by a large number offungi, or a bacterium but they rarely require chemicalcontrols. Raking up and disposing infected leaves may

reduce leaf spots next year. Algae can also cause leafspots.

Canker diseases will kill branches. Cankers onbranches can be pruned out. Keep trees healthy withregular fertilization and by watering in dry weather.

Verticillium wilt may cause death of a fewbranches or, rarely, may kill the tree. Prune out deadbranches and fertilize.