Fertilising guide
How to fertilise Zantedeschia 'Black Star' (Zantedeschia 'Black Star')— schedule & NPK
Also called Black Star calla lily, dark purple calla.
More about zantedeschia 'black star'
About Zantedeschia 'Black Star'
Zantedeschia 'Black Star' · also called Black Star calla lily, dark purple calla · flowering
Zantedeschia 'Black Star' is a dramatic hybrid calla lily with near-black, deep burgundy-purple spathes set against dark green, often speckled foliage. Grown from rhizomes, it blooms through summer in pots or borders. It needs bright indirect light, evenly moist free-draining soil in growth, and a dry winter rest, reaching about 50-60 cm tall.
Growth habit: Clump-forming rhizomatous perennial; upright arrow-shaped leaves and erect stems each bearing one furled, near-black spathe.
What fertiliser zantedeschia 'black star' actually wants — and why
Zantedeschia 'Black Star' 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 zantedeschia 'black star': 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 zantedeschia 'black star', 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 zantedeschia 'black star':
Apply a high-potassium liquid feed every 2-3 weeks during active growth to maximise the dark blooms. Go easy on nitrogen-heavy feeds, which favour foliage over flowers. Cease feeding as the plant yellows into dormancy. Treat that as every 2-3 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 zantedeschia 'black star' 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 zantedeschia 'black star'
Half strength is the safe default for zantedeschia 'black star' — 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 zantedeschia 'black star' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the zantedeschia 'black star' watering schedule.
Signs you are over-feeding zantedeschia 'black star'
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for zantedeschia 'black star':
- 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 zantedeschia 'black star'
- 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 zantedeschia 'black star' care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of zantedeschia 'black star' 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 zantedeschia 'black star'
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 zantedeschia 'black star' — frequently asked questions
What fertiliser does zantedeschia 'black star' 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. Zantedeschia 'Black Star' 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 zantedeschia 'black star'?
Apply a high-potassium liquid feed every 2-3 weeks during active growth to maximise the dark blooms. Go easy on nitrogen-heavy feeds, which favour foliage over flowers. Cease feeding as the plant yellows into dormancy. Apply a high-potassium liquid feed every 2-3 weeks during active growth to maximise the dark blooms. Go easy on nitrogen-heavy feeds, which favour foliage over flowers. Cease feeding as the plant yellows into dormancy. Treat that as every 2-3 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 zantedeschia 'black star'?
Half strength is the safe default for zantedeschia 'black star' — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding zantedeschia 'black star' 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 zantedeschia 'black star' 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 zantedeschia 'black star'?
Flush the pot of zantedeschia 'black star' 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
- Zantedeschia 'Black Star' care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water zantedeschia 'black star' — 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 peace lily
- How to fertilise bird of paradise
- How to fertilise hoya
- All 5561 fertilising guides in the Growli library