Fertilising guide
How to fertilise Canna 'Red King Humbert' (Canna 'Red King Humbert')— schedule & NPK
Also called Red King Humbert canna, Canna lily, Humbert's canna.
More about canna 'red king humbert'
About Canna 'Red King Humbert'
Canna 'Red King Humbert' · also called Red King Humbert canna, Canna lily · flowering
Canna 'Red King Humbert' is a classic heritage canna cultivar with dramatic bronze-purple foliage and vivid scarlet-red flowers, creating a bold tropical effect in summer borders and containers. A vigorous, tall grower reaching 1.5-2 m, it has been cultivated since the early 20th century. Mildly toxic to some animals.
Growth habit: Tall upright rhizomatous perennial
Watch for — Canna leaf roller: Caterpillar larvae roll leaves and feed inside. Remove manually or apply Bacillus thuringiensis where infestations are severe.
What fertiliser canna 'red king humbert' actually wants — and why
Canna 'Red King Humbert' 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 canna 'red king humbert': 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 canna 'red king humbert', 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 canna 'red king humbert':
Feed fortnightly with a high-potassium liquid fertiliser throughout the growing season. The large plant mass requires consistent nutrition to sustain growth and flowering over summer. 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 canna 'red king humbert' 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 canna 'red king humbert'
Half strength is the safe default for canna 'red king humbert' — 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 canna 'red king humbert' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the canna 'red king humbert' watering schedule.
Signs you are over-feeding canna 'red king humbert'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for canna 'red king humbert':
- 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 canna 'red king humbert'
- 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 canna 'red king humbert' care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of canna 'red king humbert' 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 canna 'red king humbert'
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 canna 'red king humbert' — frequently asked questions
What fertiliser does canna 'red king humbert' 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. Canna 'Red King Humbert' 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 canna 'red king humbert'?
Feed fortnightly with a high-potassium liquid fertiliser throughout the growing season. The large plant mass requires consistent nutrition to sustain growth and flowering over summer. Feed fortnightly with a high-potassium liquid fertiliser throughout the growing season. The large plant mass requires consistent nutrition to sustain growth and flowering over summer. 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 canna 'red king humbert'?
Half strength is the safe default for canna 'red king humbert' — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding canna 'red king humbert' 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 canna 'red king humbert' 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 canna 'red king humbert'?
Flush the pot of canna 'red king humbert' 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
- Canna 'Red King Humbert' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water canna 'red king humbert' — 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 pelotazo mallow
- How to fertilise few-flowered abutilon
- How to fertilise hatschbach's fuchsia
- All 11687 fertilising guides in the Growli library