Fertilising guide
How to fertilise Purple Allamanda (Allamanda blanchetii)— schedule & NPK
Also called Purple Allamanda, Cherry Allamanda, Pink Allamanda, Violet Allamanda.
More about purple allamanda
About Purple Allamanda
Allamanda blanchetii · also called Purple Allamanda, Cherry Allamanda · tropical
A vigorous tropical shrubby climber from Brazil producing successive flushes of reddish-purple to rose-pink trumpet flowers for months in summer and autumn, and year-round in frost-free conditions. Spectacular on fences and pergolas or trimmed into a free-standing shrub. Requires full sun, heat, and consistent moisture to flower at its best.
Growth habit: Vigorous, semi-climbing or sprawling evergreen tropical shrub; can be trained as a climber or kept pruned as a rounded shrub
What fertiliser purple allamanda actually wants — and why
Purple Allamanda 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 allamanda: 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 allamanda, 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 allamanda:
Feed every 3–4 weeks during the growing season with a balanced fertiliser (10-10-10), then switch to a high-potassium, low-nitrogen formula (e.g. tomato feed) to prolong flowering. Avoid excess nitrogen, which promotes lush foliage at the expense of blooms. Do not fertilise in winter. 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 allamanda 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 allamanda
Half strength is the safe default for purple allamanda — 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 allamanda first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the purple allamanda watering schedule.
Signs you are over-feeding purple allamanda
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for purple allamanda:
- 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 allamanda
- 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 allamanda care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of purple allamanda 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 allamanda
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 allamanda — frequently asked questions
What fertiliser does purple allamanda 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 Allamanda 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 allamanda?
Feed every 3–4 weeks during the growing season with a balanced fertiliser (10-10-10), then switch to a high-potassium, low-nitrogen formula (e.g. tomato feed) to prolong flowering. Avoid excess nitrogen, which promotes lush foliage at the expense of blooms. Do not fertilise in winter. Feed every 3–4 weeks during the growing season with a balanced fertiliser (10-10-10), then switch to a high-potassium, low-nitrogen formula (e.g. tomato feed) to prolong flowering. Avoid excess nitrogen, which promotes lush foliage at the expense of blooms. Do not fertilise in winter. 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 allamanda?
Half strength is the safe default for purple allamanda — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding purple allamanda 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 allamanda 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 allamanda?
Flush the pot of purple allamanda 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 Allamanda care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water purple allamanda — 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 aglaonema red
- How to fertilise aglaonema silver bay
- How to fertilise aglaonema cutlass
- All 6887 fertilising guides in the Growli library