Tree · Magnoliaceae
Southern Magnolia
Magnolia grandiflora
A grand evergreen with glossy leaves and lemon-scented white blooms that anchors a landscape for generations.
Full sun
Every 7–14 days
USDA 6–10
60–80 ft · 18.3–24.4 m
Overview
The southern magnolia is the broad-leaved evergreen that gives so much of the American South its look. It grows into a stately tree of 60 to 80 feet (18 to 24 m), draped in thick, leathery leaves that shine dark green on top and often wear a rusty-brown felt underneath. From late spring into summer it opens huge white flowers, each one cup-shaped and lemon-scented, that perfume the whole yard.
This is a tree for the long haul and for plenty of room. It casts dense year-round shade and spreads wide, shallow surface roots that make growing grass beneath it a losing battle. It also drops leathery leaves, spent flowers, and cone-like fruit nearly all year, so the litter is steady. Site it where that scale and mess are welcome, well away from lawns and foundations.
Given the right spot it asks for little. It wants rich, moist, acidic soil and even watering while it settles in, then mostly looks after itself, untroubled by serious pests beyond the occasional bout of scale. Newer cultivars have pushed it well north of its old range, so cooler gardens can grow it too.
Care
The short version: full sun to part shade, rich and consistently moist acidic soil, deep watering during dry spells especially while young, and little pruning beyond clearing dead or crossing wood.
Light
Southern magnolia does best in full sun, but it takes partial sun and partial shade in stride. More sun means denser growth and heavier flowering, while a shadier spot gives you a looser, more open tree.
Water
Keep the soil consistently moist, watering deeply during dry spells and especially while the tree is establishing. Once settled it gets by on roughly a soak every 7 to 14 days in dry weather, but it won't tolerate either prolonged drought or standing water.
Soil
Plant in rich, organically rich, well-drained loam that stays moist. The tree leans acidic, happiest at a pH of 5.0 to 6.5, and though it puts up with clay it resents waterlogged or extreme ground.
Temperature
It handles a wide swing, from about -9°F to 100°F (-23°C to 38°C), which covers Zones 6 through 10. Cold-hardy cultivars are the safer bet at the northern edge of that range.
Humidity
Ordinary outdoor humidity suits it, so there's no target to hit. Warm, muggy weather can bring on algal leaf spot, but that's cosmetic and easily lived with.
Feeding
Feed once in spring with a balanced or acid-forming slow-release fertilizer made for acid-loving trees. Go easy, since too much nitrogen pushes soft growth that scale insects love.
Pruning
This tree needs little pruning. Take out dead, damaged, or crossing branches in late winter to early spring, and leave the low limbs to sweep the ground if you'd rather they hide the leaf litter than show bare trunk.
Repotting
An in-ground tree never needs repotting, and even container stock is moved rarely. Signs a nursery plant has outgrown its pot include roots circling the rootball, roots pushing through the drainage holes, and water running straight through.
Size & spacing
Plan for a big tree, 60 to 80 feet (18 to 24 m) tall and 30 to 50 feet (9 to 15 m) wide. Give it that full footprint of open space, clear of buildings and lawn, so the canopy and surface roots have room.
When to plant
This is a tree you set out, not a crop you time to the season. Plant it in spring or fall while the weather is mild, and from then on the calendar is about its show, the big white flowers that open from late spring into summer, heaviest in May and June and trickling on after that.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring or fall
- Harvest: Late spring to summer (May to June, with sparse continued flowering through summer)
Hardiness
USDA hardiness zones: 6–10
Temperature: down to -23°C
Troubleshooting
A healthy southern magnolia rarely gives much trouble, and the few issues it does face show up on the twigs or leaves. Catch them early and most are easy to manage. Match what you see below, then act before it spreads.
Whole branches wilting and dying back one at a time
When scattered branches wilt and brown out on their own, the cause is usually verticillium wilt, a soil fungus that plugs the wood from the inside. Cut the bark and you may find dark streaks in the vascular tissue, though a lab test is the only sure call. There's no chemical cure, so prune out the dead wood and keep the tree strong with steady water and feeding.
Fix:
- Prune out and destroy affected dead branches
- Fertilize and water during dry weather to support recovery
- There is no chemical cure; keep the tree vigorous
Waxy white bumps on the twigs with a sticky, blackened film below
Those raised, shell-like bumps are magnolia scale, one of the few pests that bothers this tree. As the scales feed they drip honeydew, and a black sooty mold grows on it across the leaves underneath. Prune out the worst twigs, hit overwintering scale with horticultural oil in the dormant season, and treat the crawlers in late summer.
Fix:
- Prune out and destroy heavily infested twigs
- Apply horticultural oil during the dormant season to smother overwintering scale
- Treat crawlers in late summer when young scales are active
Spots and blotches on the leaves, sometimes with early leaf drop
Most leaf spots on this tree are fungal or bacterial, and in warm, humid weather you may also see the greenish-gray patches of algal leaf spot. None of it does lasting harm. Rake up and bin the fallen leaves, open the canopy with light pruning so air moves through, and skip the sprays, which are rarely worth it here.
Fix:
- Rake up and dispose of infected fallen leaves
- Improve air circulation by spacing and selective pruning
- Chemical control is rarely needed
Toxicity
Good news for pet owners: the southern magnolia is safe. The ASPCA lists magnolia as non-toxic to cats, dogs, and horses, and nothing in the tree poisons people, livestock, birds, or rabbits. The worst a big mouthful of leaves might cause is brief, mild stomach upset, the same as with many plants.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The ASPCA lists magnolia as non-toxic to cats, so a nibbled leaf is no cause for alarm. A cat that gorges on foliage might drool or throw up once, the way any rough plant material can upset a stomach.
Dogs None
Dogs can chew the leaves without any poisoning risk. The most you'll likely see from a big mouthful is a brief bout of vomiting or loose stool while the fibrous material passes through.
Horses None
Horses are clear too, with magnolia on the ASPCA's non-toxic list. The tough, leathery leaves aren't a favorite browse, and a stray mouthful does no harm.
Rabbits Safe
No toxin here threatens a rabbit. Their gut handles only small amounts of new greenery well, so treat the odd leaf as a curiosity rather than part of the diet.
Livestock Safe
Cattle, goats, and sheep can graze near a southern magnolia safely, since nothing in the tree is poisonous to them. They tend to ignore the stiff evergreen leaves anyway.
Birds Safe
The tree poses no chemical danger to birds, which often shelter and nest in its dense canopy. Some will pick at the bright red seeds in fall without trouble.
People Safe
Southern magnolia is not poisonous to people, and no part is known to harm anyone who handles it. The leaves and flowers aren't a food, though, so there's no reason to eat them.
As with any plant, ingestion of plant material may cause mild, transient gastrointestinal upset even though the plant is non-toxic.
Varieties
Several named selections refine the wild tree, trading some height for cold tolerance, smaller leaves, or a tidier shape. These are the ones worth knowing.
Little Gem
A compact semi-dwarf that tops out near 30 feet with smaller leaves and flowers, blooms while still young, and fits a yard too small for the full-size tree.
Bracken's Brown Beauty
A cold-hardy, compact selection that holds up to Zone 6, with smaller leaves backed by a thick, rusty-brown felt underneath.
Edith Bogue
One of the toughest picks for harsh sites, prized for shrugging off cold, wind, and heavy snow.
D.D. Blanchard
A vigorous grower that reaches about 75 feet on a straight trunk, with dark glossy leaves and rich brown undersides.
How to propagate
You can raise a southern magnolia from seed or clone an existing one, though every method asks for patience. Which you choose depends on whether you need to keep a particular cultivar's traits.
SeedModerate
Sow cleaned seed in fall or after cold stratification · Several months to germinate; years to reach flowering size
Strip off the red fleshy coat, then sow the cleaned seed in fall or give it a cold spell first. Germination takes several months, and a seedling needs years to reach flowering size, building a strong taproot as it goes. Seed won't reproduce a named cultivar, so use it only when you're happy with whatever you get.
Air layeringModerate
Spring to summer on actively growing wood · Several months to root
Air-layering is the most dependable way to clone a southern magnolia and keep its cultivar traits. Work on actively growing wood from spring through summer and give it several months to root before you sever the new plant.
Stem cuttingsDemanding
Semi-hardwood cuttings in summer · Several weeks to months under mist
Take semi-hardwood cuttings in summer, dip them in rooting hormone, and keep them under mist. Rooting runs slow and uneven here, taking anywhere from several weeks to a few months, which is why this method tests your patience.
GraftingDemanding
Late winter to spring · One or more seasons to unite
Grafting from late winter into spring joins a named cultivar onto seedling rootstock so the new tree keeps its parent's traits. The union needs one or more seasons to knit firmly, and the technique takes a skilled hand.
Myths
Southern magnolia is poisonous to dogs and cats.
The ASPCA lists magnolia as non-toxic to dogs, cats, and horses, so a curious pet that chews a leaf is in no danger. The worst you might see is brief, mild stomach upset, the same thing any plant material can cause. You can plant it around pets without worry.