Fertilising guide
How to fertilise Black Calla Lily (Zantedeschia 'Black Star')— schedule & NPK
Also called Black Calla Lily, Black Star Calla.
More about black calla lily
About Black Calla Lily
Zantedeschia 'Black Star' · also called Black Calla Lily, Black Star Calla · flowering
Zantedeschia 'Black Star' is a striking hybrid calla lily producing intensely deep maroon-black spathes on tall stems above lush, dark green, sometimes spotted foliage. A highly sought-after cut flower and container plant, it thrives in full sun with consistent moisture during growth and a dry winter dormancy. All parts are toxic to cats, dogs, and humans due to calcium oxalate raphides.
Growth habit: Rhizomatous, seasonally dormant perennial; upright clump-forming habit
Watch for — Fading spathe colour: The deep black-maroon pigmentation fades in insufficient light or heat. Ensure at least 6 hours of bright light and do not position in cool, shaded spots. High-potassium feeding also helps sustain colour intensity.
What fertiliser black calla lily actually wants — and why
Black Calla Lily 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 black calla lily: 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 black calla lily, 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 black calla lily:
Apply a high-potassium liquid fertiliser (tomato feed formula) every 2 weeks from when shoots emerge until the flower spathes begin to fade. This promotes the deep pigmentation and strong stem development the cultivar is selected for. Switch to a balanced feed at planting if soil has not been pre-enriched. Treat that as every 2 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 black calla lily 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 black calla lily
Half strength is the safe default for black calla lily — 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 black calla lily first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the black calla lily watering schedule.
Signs you are over-feeding black calla lily
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for black calla lily:
- 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 black calla lily
- 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 black calla lily care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of black calla lily 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 black calla lily
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 black calla lily — frequently asked questions
What fertiliser does black calla lily 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. Black Calla Lily 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 black calla lily?
Apply a high-potassium liquid fertiliser (tomato feed formula) every 2 weeks from when shoots emerge until the flower spathes begin to fade. This promotes the deep pigmentation and strong stem development the cultivar is selected for. Switch to a balanced feed at planting if soil has not been pre-enriched. Apply a high-potassium liquid fertiliser (tomato feed formula) every 2 weeks from when shoots emerge until the flower spathes begin to fade. This promotes the deep pigmentation and strong stem development the cultivar is selected for. Switch to a balanced feed at planting if soil has not been pre-enriched. Treat that as every 2 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 black calla lily?
Half strength is the safe default for black calla lily — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding black calla lily 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 black calla lily 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 black calla lily?
Flush the pot of black calla lily 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
- Black Calla Lily care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water black calla lily — 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 running tapestry foamflower
- How to fertilise virginia bluebells
- How to fertilise mountain bluebells
- All 8452 fertilising guides in the Growli library