Fertilising guide
How to fertilise Thunbergia erecta (Thunbergia erecta)— schedule & NPK
Also called Bush clock vine, King's mantle.
More about thunbergia erecta
About Thunbergia erecta
Thunbergia erecta · also called Bush clock vine, King's mantle · tropical
Thunbergia erecta, the bush clock vine or King's mantle, is an evergreen West African shrub grown for its near-continuous trumpet-shaped purple-blue flowers with golden throats. Unlike its climbing relatives it forms a tidy, self-supporting bush. It thrives in warm, frost-free gardens and makes a free-flowering container or conservatory plant in cooler climates.
Growth habit: Evergreen, densely branching shrub with arching stems; can be kept compact by pruning or allowed to sprawl as a loose informal hedge.
Watch for — Sparse flowering: Usually too little light or excess nitrogen. Move to full sun and switch to a phosphorus-rich feed to restore bloom.
What fertiliser thunbergia erecta actually wants — and why
Thunbergia erecta 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 thunbergia erecta: 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 thunbergia erecta, 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 thunbergia erecta:
Feed every 2-4 weeks through spring and summer with a balanced or slightly phosphorus-rich liquid fertiliser to sustain bloom. Ease off in autumn and stop in winter when growth slows. Treat that as every 2-4 weeks 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 thunbergia erecta 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 thunbergia erecta
Half strength is the safe default for thunbergia erecta — 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 thunbergia erecta first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the thunbergia erecta watering schedule.
Signs you are over-feeding thunbergia erecta
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for thunbergia erecta:
- 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 thunbergia erecta
- 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 thunbergia erecta care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of thunbergia erecta 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 thunbergia erecta
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 thunbergia erecta — frequently asked questions
What fertiliser does thunbergia erecta 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. Thunbergia erecta 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 thunbergia erecta?
Feed every 2-4 weeks through spring and summer with a balanced or slightly phosphorus-rich liquid fertiliser to sustain bloom. Ease off in autumn and stop in winter when growth slows. Feed every 2-4 weeks through spring and summer with a balanced or slightly phosphorus-rich liquid fertiliser to sustain bloom. Ease off in autumn and stop in winter when growth slows. Treat that as every 2-4 weeks 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 thunbergia erecta?
Half strength is the safe default for thunbergia erecta — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding thunbergia erecta 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 thunbergia erecta 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 thunbergia erecta?
Flush the pot of thunbergia erecta 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
- Thunbergia erecta care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water thunbergia erecta — 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 monstera
- How to fertilise pothos
- How to fertilise fiddle leaf fig
- All 5561 fertilising guides in the Growli library