Repotting guide

When & how to repot Magnolia grandiflora 'Gallissonnière' (Magnolia grandiflora 'Gallissonnière')

Also called Southern Magnolia, Gallissonniere Magnolia.

More about magnolia grandiflora 'gallissonnière'

About Magnolia grandiflora 'Gallissonnière'

Magnolia grandiflora 'Gallissonnière' · also called Southern Magnolia, Gallissonniere Magnolia · flowering

A vigorous, hardier selection of the evergreen Southern magnolia, 'Gallissonnière' bears glossy leathery leaves with rusty felted undersides and large, lemon-scented creamy-white flowers through summer into autumn. It tolerates colder, exposed sites better than the species and is often wall-trained in the UK. Slow to establish but long-lived and stately once settled.

Mature size: 6-10 m tall and 4-6 m wide over decades, smaller and more compact than the species; growth is slow, roughly 20-30 cm per year once established.

Watch for — Slow establishment: Resents root disturbance and may sulk for a year or two after planting; plant in late spring, water consistently and avoid moving once sited.

How to tell magnolia grandiflora 'gallissonnière' needs repotting

Repotting on a calendar is less reliable than reading the plant. For magnolia grandiflora 'gallissonnière', watch for these signs:

Thick roots out of the drainage holes, or circling the surface and lifting the plant.
The pot dries out unusually fast and magnolia grandiflora 'gallissonnière' wilts between waterings it used to shrug off.
The plant is visibly top-heavy and tips over easily.
Stalled growth and small new leaves over a full season — though with a big specimen, top-dressing is often the better first response before a full repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot magnolia grandiflora 'gallissonnière'

Every 2–3 years; top-dress in the in-between years. Magnolia grandiflora 'Gallissonnière''s growth habit — broadly pyramidal to rounded evergreen tree with a dense, branching canopy clothed to the ground unless limbed up; often grown wall-trained or as a free-standing specimen. — sets the pace. A vigorous, hardier selection of the evergreen Southern magnolia, 'Gallissonnière' bears glossy leathery leaves with rusty felted undersides and large, lemon-scented creamy-white flowers through summer into autumn. It tolerates colder, exposed sites better than the species and is often wall-trained in the UK. Slow to establish but long-lived and stately once settled.

What size pot to step magnolia grandiflora 'gallissonnière' up to

Move up exactly one pot size. A heavy magnolia grandiflora 'gallissonnière' dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot magnolia grandiflora 'gallissonnière'

Early spring, just as new growth restarts, is the ideal window for magnolia grandiflora 'gallissonnière'. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting magnolia grandiflora 'gallissonnière'

Consider top-dressing first. If magnolia grandiflora 'gallissonnière' is not badly root-bound, scrape off and replace the top 3–5 cm of soil instead — far less shock for a big plant that hates moving.
Get help and one size up. For a full repot, choose a pot just one size larger. A heavy plant needs two people and a stable, free-draining pot.
Ease it out on its side. Lay the plant down, slide the pot off, and gently loosen the outer roots. Do not bare-root a mature specimen.
Repot at the same depth. Add fresh deep, fertile, moisture-retentive loam, slightly acidic to neutral beneath and around the rootball, keeping the original soil line. Firm it so the trunk is stable and upright.
Water and leave it put. Water thoroughly, then leave magnolia grandiflora 'gallissonnière' in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave magnolia grandiflora 'gallissonnière' in exactly the same spot and light it was in before — moving and repotting at the same time is what makes a big specimen drop leaves. Water it in well, then let the top of the soil dry before watering again so the larger volume of fresh soil does not stay sodden. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for magnolia grandiflora 'gallissonnière'

Magnolia grandiflora 'Gallissonnière' wants deep, fertile, moisture-retentive loam, slightly acidic to neutral. Prefers rich, well-drained acid to neutral soil (pH ~5.5-6.5) high in organic matter. Tolerates clay if not waterlogged and dislikes shallow chalk, which causes chlorosis. Mulch annually with leaf mould or composted bark to feed the surface roots. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting magnolia grandiflora 'gallissonnière' — frequently asked questions

How often should you repot magnolia grandiflora 'gallissonnière'?

Every 2–3 years; top-dress in the in-between years for magnolia grandiflora 'gallissonnière'. Fully repot magnolia grandiflora 'gallissonnière' only every 2–3 years; in the in-between years just top-dress the top 3–5 cm of soil. Step up one pot size in spring with deep, fertile, moisture-retentive loam, slightly acidic to neutral. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does magnolia grandiflora 'gallissonnière' need?

When is the best time of year to repot magnolia grandiflora 'gallissonnière'?

Should you top-dress or fully repot magnolia grandiflora 'gallissonnière'?

For a big, heavy magnolia grandiflora 'gallissonnière', top-dressing — replacing the top 3–5 cm of soil — is the gentler option most years, with a full repot only every 2–3 years. A mature specimen sulks and drops leaves when fully repotted, so do it as rarely as the roots allow.

Should you fertilise magnolia grandiflora 'gallissonnière' after repotting?

Not immediately. Wait about 4 weeks after repotting magnolia grandiflora 'gallissonnière'. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.