Fertilising guide
How to fertilise Purple Glory Tree (Tibouchina granulosa)— schedule & NPK
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.
Growth habit: Fast-growing, upright, semi-evergreen tree or large multi-stemmed shrub; responds well to hard pruning after flowering to maintain bushy form.
Watch for — Interveinal chlorosis: Yellowing between leaf veins while the veins stay green indicates iron or manganese deficiency, usually triggered by alkaline soil or compost; treat with a chelated iron (sequestrene) drench and use an acidifying fertiliser to lower pH.
What fertiliser purple glory tree actually wants — and why
Purple Glory Tree is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for purple glory tree: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed purple glory tree, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For purple glory tree:
Apply a balanced slow-release granular fertiliser in spring; supplement with a high-potash liquid feed every two weeks during the flowering season to support continued bloom production. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when purple glory tree is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for purple glory tree
Half strength is the safe default for purple glory tree — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water purple glory tree first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the purple glory tree watering schedule.
Signs you are over-feeding purple glory tree
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for purple glory tree:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding purple glory tree
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full purple glory tree care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of purple glory tree with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for purple glory tree
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising purple glory tree — frequently asked questions
What fertiliser does purple glory tree need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Purple Glory Tree is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed purple glory tree?
Apply a balanced slow-release granular fertiliser in spring; supplement with a high-potash liquid feed every two weeks during the flowering season to support continued bloom production. Apply a balanced slow-release granular fertiliser in spring; supplement with a high-potash liquid feed every two weeks during the flowering season to support continued bloom production. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for purple glory tree?
Half strength is the safe default for purple glory tree — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding purple glory tree look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding purple glory tree year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of purple glory tree?
Flush the pot of purple glory tree with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Purple Glory Tree care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water purple glory tree — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise indian gooseberry
- How to fertilise velvet tamarind
- How to fertilise marang
- All 10153 fertilising guides in the Growli library