Repotting guide

When & how to repot Princess Flower (Tibouchina urvilleana)

Also called Princess flower, Glory bush, Purple glory tree, Lasiandra, Pleroma urvilleanum.

More about princess flower

About Princess Flower

Tibouchina urvilleana · also called Princess flower, Glory bush · flowering

Princess flower (Tibouchina urvilleana) is a tropical evergreen shrub prized for velvety leaves and royal-purple, five-petalled blooms. Give it full sun, consistently moist acidic soil, warmth, and frost protection. It is not individually listed by the ASPCA, so treat it as a possible mild irritant around pets and verify with your vet.

Mature size: Typically 6-8 ft (1.8-2.4 m) tall and 3-5 ft (0.9-1.5 m) wide in cultivation; can reach 10-20 ft (3-6 m) as a tree in frost-free climates. Much smaller and controllable when grown in containers.

Watch for — Root rot: Mushroom root rot develops in soil kept too wet. Use a free-draining mix, empty saucers, and let the top of the soil dry slightly between waterings.

How to tell princess flower needs repotting

Repotting on a calendar is less reliable than reading the plant. For princess flower, 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 princess flower 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 princess flower

Every 2–3 years; top-dress in the in-between years. Princess Flower's growth habit — fast-to-moderate, somewhat sprawling evergreen shrub or small tree with an erect, vase-shaped to rounded form; benefits from pinching and light pruning to stay bushy and tree-like. — sets the pace. Princess flower (Tibouchina urvilleana) is a tropical evergreen shrub prized for velvety leaves and royal-purple, five-petalled blooms. Give it full sun, consistently moist acidic soil, warmth, and frost protection. It is not individually listed by the ASPCA, so treat it as a possible mild irritant around pets and verify with your vet.

What size pot to step princess flower up to

Move up exactly one pot size. A heavy princess flower 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 princess flower

Early spring, just as new growth restarts, is the ideal window for princess flower. 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 princess flower

Consider top-dressing first. If princess flower 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 rich, acidic, well-draining potting mix 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 princess flower in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave princess flower 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 princess flower

Princess Flower wants rich, acidic, well-draining potting mix. Prefers high-organic, well-drained soil on the acidic side (pH below 6.0). A peat- or coir-based mix amended with perlite and composted bark works well. Alkaline soils can trigger chlorosis (yellowing leaves with green veins). Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting princess flower — frequently asked questions

How often should you repot princess flower?

Every 2–3 years; top-dress in the in-between years for princess flower. Fully repot princess flower 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 rich, acidic, well-draining potting mix. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does princess flower need?

When is the best time of year to repot princess flower?

Should you top-dress or fully repot princess flower?

For a big, heavy princess flower, 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 princess flower after repotting?

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