How to grow magnolia
Overview
Magnolia grandiflora is a large, evergreen tree grown for its glossy, dark green foliage and spectacular, fragrant white summer flowers. It provides structure, shade, and year-round presence in the landscape. Growers must allow ample space and plant in deep, well-drained, acidic soil.
Varieties
- Little Gem — Compact, dwarf cultivar with smaller leaves and flowers; ideal for smaller gardens or large pots.
- Green Giant — Vigorous grower reaching 20 m, with large flowers and good heat tolerance; popular in warmer regions.
- Exmouth — Noted for exceptionally large, fragrant flowers and a sturdy, broad form; tough and adaptable.
- St Mary — A reliable early-flowering form with creamy white blooms; syn. 'St. Mary's'.
Soil Preparation
Prefers acidic to neutral soil (pH 5.5–7.0) that is deep, rich in organic matter, and well-drained. Amend heavy clay with gypsum and compost; improve sandy soil with well-rotted manure. Raised beds can help if drainage is poor.
Growing Guide
Plant in full sun to part shade; protect from harsh afternoon sun in hotter climates. Choose a deep, rich, well-drained soil with added organic matter. Dig a hole twice as wide as the root ball and plant at the same depth as the pot. Space trees 6–10 m apart to accommodate eventual spread. Water deeply and regularly during the first two years, then as needed. Mulch heavily with wood chips or pine bark to keep roots cool and moist.
Care
Feed in early spring with a balanced slow-release fertiliser formulated for acid-loving plants. Prune only to remove dead, damaged, or crossing branches in late winter; magnolia resents heavy pruning. Each year, replenish mulch with compost or pine bark to maintain cool, moist root conditions.
Companion Planting
Underplant with shade-tolerant, acid-loving plants such as Camellia japonica, Rhododendron, and Azalea. Ferns (e.g., Blechnum) and Hosta also thrive in the dappled light beneath its canopy. Avoid planting shallow-rooted annuals or turf right up to the trunk, as magnolia roots are surface-spreading and easily disturbed.
Common Pests & Risks
Scale insects (e.g., magnolia scale) and aphids can cause sticky honeydew and sooty mould; treat with horticultural oil in spring. Leaf spot (fungal) occurs in humid conditions; prune to improve air circulation and remove infected leaves. Check for thrips and caterpillars occasionally; control with insecticidal soap if severe.
Troubleshooting
Yellow leaves with green veins: iron chlorosis from alkaline soil or poor drainage – apply iron chelates and improve drainage. Brown leaf edges: windburn or frost damage – plant in a sheltered position or protect young trees. Sparse or no flowers: insufficient sun or overpruning – ensure at least 6 hours of direct sun and avoid heavy cutting. Scale insects: sticky leaves and sooty mould – spray with horticultural oil in early spring. Root rot: wilting or dieback in poorly drained clay – improve drainage or plant on a mound.