Southern magnolia

Southern magnolia: how do you recognise it?

Habit

Broad, pyramidal to rounded tree or large shrub; slow-growing, usually 5–10 m here. Against a wall it can be trained flat.

Leaves

Oval, leathery, 12–20 cm long, glossy dark green; undersides often rusty-brown and hairy. The oldest leaves drop in spring.

Flowers

Cup-shaped, creamy white, 15–25 cm across, with thick petals. Each flower lasts only a few days, but more follow until September.

Scent

Strong and fresh with a hint of lemon; most noticeable on warm days.

Fruit

A hairy, cone-like fruit with red seeds; here it does not form every year.

Roots

Fleshy, fairly shallow and easily damaged: do not dig under the canopy and avoid moving it.

Flowering: July–September · Plants: April–May and September · Pruning: April

Why grow it?

• Evergreen: a glossy, almost tropical canopy all year round.
• Large, lemon-scented flowers in midsummer, when most trees and shrubs have finished.
• A striking feature against a sunny wall or as a specimen in a sheltered garden.
• The rusty-brown leaf undersides contrast beautifully with the dark green upper surface.
• Long-lived and low-maintenance: once established it needs hardly any pruning.

Southern magnolia: where does it grow best?

• Sun to partial shade; for good flowering choose a warm, sunny spot, ideally against a south- or west-facing wall.
• Sheltered from cold east and north winds, which scorch the evergreen leaves.
• Humus-rich, free-draining sandy or loamy soil, acid to neutral; on chalky soil the leaves turn yellow.
• Normal moisture: it should not dry out in summer or sit wet in winter.
• Allow at least 4–5 m; against a wall 3–4 m wide, planted 50 cm from the wall.

Light

Sun and partial shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal

Size

10 m tall, 8 m wide

Hardiness

Hardy (to -15 °C)

Goes well with

• Agapanthus: Blue globes at the foot of a sunny wall in the same part of summer.
• Hydrangea: Also likes acid to neutral, moisture-retentive soil and flowers at the same time.
• Clematis: A summer-flowering clematis beside the magnolia on the same wall adds colour.
• Ferns: A green underplanting in the shade beneath the canopy.
• Japanese anemone: Flowers in late summer in pink or white, in sun or partial shade.

Southern magnolia: when and how to plant it?

Plant in April–May and September.

1. Plant in April–May or in September, so the roots can settle before winter.
2. Buy a pot-grown or container plant: magnolias establish poorly from bare roots.
3. Dig a hole twice as wide as the root ball and mix leaf mould or ericaceous compost into the soil.
4. Set the root ball at the same depth as in the pot, no deeper, and firm the soil gently.
5. Water in thoroughly and keep watering in dry spells throughout the first year.
6. Mulch around the base with leaf mould or bark, and stake a young tree or tie it to wires on the wall.

Care

Watering

For the first two years, water generously every week in dry weather. After that, only in long, dry summers.

Feeding

In April, some compost or an organic feed for acid-loving plants. No feeding after July.

Mulching

A layer of leaf mould or bark each spring keeps the shallow roots cool and moist.

Leaf drop

The oldest leaves fall in spring. That is normal; rake them up, as they rot down slowly.

Training

Against a wall, tie the young shoots loosely to horizontal wires or a trellis.

Tip: Buy a plant that has already flowered in the nursery, or a cultivar such as ‘Little Gem’: seedlings can take many years to produce their first flower.

Southern magnolia: when to prune it?

Pruning months: April.

When: In April, when the worst frosts are over and new growth starts. Prune as little as possible.

How:

• Remove only dead, frosted or damaged wood, cutting just above a healthy leaf or side shoot.
• On a wall, cut out shoots growing away from it and tie the rest in along the wires.
• Shorten over-long branches back to a side shoot, without leaving stubs.
• Saw large branches off in stages so the bark does not tear.

Caution: Never prune in autumn or winter: the wounds heal poorly and the plant becomes more prone to frost damage. If it needs cutting back hard, spread the work over two or three years.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Layering

In spring, nick the underside of a low, flexible branch, bury it and peg it down. After one or two years it has rooted and can be severed.

Semi-ripe cuttings

In July–August, take 15 cm cuttings with a heel and root them in moist compost with bottom heat. Success is not guaranteed and it takes patience.

Seed

In autumn, take the red seeds from the fruit, remove the fleshy coat and leave them outside in a pot over winter. Seedlings take many years to flower.

Southern magnolia: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Hardy to about −15 °C: it succeeds in most Belgian gardens in a sheltered spot, ideally against a warm wall.
• In the first winters, protect young plants in hard frost with horticultural fleece over the crown and a mulch over the roots.
• Shake wet snow off the branches: the large leaves hold a lot of snow and branches break easily.
• In a container (for example ‘Little Gem’), move it against the house in winter and wrap the pot in hessian or bubble wrap.

Diseases and pests

• Brown, scorched leaves: Cold wind or hard frost turns leaves brown. Wait until April before cutting out frosted parts; a sheltered spot prevents it.
• Yellow leaves: Many yellow leaves in summer usually mean the soil is too chalky or too wet. Add leaf mould or an ericaceous feed and improve drainage. A few yellow leaves in spring are normal.
• No flowers: Young plants, and seedlings in particular, take some years to flower. Too much shade or too much nitrogen also holds back flowering.
• Scale insects: Small brown bumps on stems and under leaves, often with sticky honeydew and black sooty mould. Brush them off with a soft brush and soapy water.

Through the year

• January: Shake wet snow off the branches. Protect young plants in hard frost.
• February: Dormant. Check the ties on the wall.
• March: Remove the fleece when milder weather arrives. Top up the mulch.
• April: Prune if needed. Plant. Add compost or feed.
• May: Plant. Old leaves drop: rake them up.
• June: Water in dry spells. Tie in new shoots.
• July: First flowers. Water in dry spells.
• August: Flowering. Take semi-ripe cuttings. Water in dry spells.
• September: Last flowers. Plant while the soil is still warm.
• October: Collect seed if fruits have formed. Mulch.
• November: Wrap containers. Prepare young plants for winter.
• December: Keep fleece at hand for hard frosts.

Did you know?

• Magnolias are a very ancient genus, probably older than bees. Their flowers have long been pollinated by beetles, which is why they are so tough.
• The genus is named after Pierre Magnol, a French botanist from Montpellier.
• The magnolia is the state flower of Mississippi and Louisiana in the United States.