Repotting guide

When & how to repot Purple Glory Tree (Tibouchina granulosa)

Also called Purple Glory Tree, Brazilian Glory Tree, Glorybush.

More about purple glory tree

About Purple Glory Tree

Tibouchina granulosa · also called Purple Glory Tree, Brazilian Glory Tree · tropical

Tibouchina granulosa is a fast-growing, semi-evergreen tree or large shrub native to the Atlantic Forest of south-eastern Brazil, widely planted in tropical and subtropical regions for its spectacular displays of large, saucer-shaped purple flowers borne in dense terminal clusters. In frost-free climates it can reach 6–15 m tall, but responds well to pruning to maintain a manageable size in gardens or containers. Full sun and a fertile, acidic, well-drained soil are essential for maximum flowering. Tibouchina is considered non-toxic to cats, dogs, and humans by the California Poison Control System; it is not listed by the ASPCA as a toxic plant.

Mature size: 6–15 m tall and 4–8 m wide in the ground in frost-free climates; container-grown specimens typically kept to 2–4 m with regular pruning.

How to tell purple glory tree needs repotting

Repotting on a calendar is less reliable than reading the plant. For purple glory tree, 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 purple glory tree 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 purple glory tree

Every 2–3 years; top-dress in the in-between years. Purple Glory Tree's growth habit — fast-growing, upright, semi-evergreen tree or large multi-stemmed shrub; responds well to hard pruning after flowering to maintain bushy form. — sets the pace. Tibouchina granulosa is a fast-growing, semi-evergreen tree or large shrub native to the Atlantic Forest of south-eastern Brazil, widely planted in tropical and subtropical regions for its spectacular displays of large, saucer-shaped purple flowers borne in dense terminal clusters. In frost-free climates it can reach 6–15 m tall, but responds well to pruning to maintain a manageable size in gardens or containers. Full sun and a fertile, acidic, well-drained soil are essential for maximum flowering. Tibouchina is considered non-toxic to cats, dogs, and humans by the California Poison Control System; it is not listed by the ASPCA as a toxic plant.

What size pot to step purple glory tree up to

Move up exactly one pot size. A heavy purple glory tree 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 purple glory tree

Early spring, just as new growth restarts, is the ideal window for purple glory tree. 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 purple glory tree

Consider top-dressing first. If purple glory tree 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 fertile, well-draining, acidic soil (ph 5.0–6.5) 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 purple glory tree in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave purple glory tree 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 purple glory tree

Purple Glory Tree wants fertile, well-draining, acidic soil (ph 5.0–6.5). Use an ericaceous (acidic) potting compost for container growing; add perlite or coarse grit to improve drainage. Alkaline soils cause interveinal chlorosis — use an acidifying fertiliser if pH rises above 6.5. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting purple glory tree — frequently asked questions

How often should you repot purple glory tree?

Every 2–3 years; top-dress in the in-between years for purple glory tree. Fully repot purple glory tree 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 fertile, well-draining, acidic soil (ph 5.0–6.5). It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does purple glory tree need?

When is the best time of year to repot purple glory tree?

Should you top-dress or fully repot purple glory tree?

For a big, heavy purple glory tree, 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 purple glory tree after repotting?

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