Fertilising guide
How to fertilise Slipper Flower (Calceolaria integrifolia)— schedule & NPK
Also called Slipper Flower, Slipperwort, Bush Calceolaria, Yellow Pouch Flower.
More about slipper flower
About Slipper Flower
Calceolaria integrifolia · also called Slipper Flower, Slipperwort · flowering
Calceolaria integrifolia is a compact, semi-woody sub-shrub native to Chile, producing masses of cheerful yellow pouch-shaped flowers (occasionally orange or red in cultivars) from late spring through summer. Unlike the tender indoor Calceolaria hybrids, this species is more robust and suits outdoor container displays, summer bedding, and borders in sheltered gardens. It flowers most abundantly in cool conditions and quickly declines in summer heat above 25 °C (77 °F), making cool-season planting the key to success. The Calceolaria genus is widely cited as non-toxic by pet-safety compilers; however, it is not definitively confirmed as individually assessed by the ASPCA, so it is listed here as mildly-toxic as a precaution.
Growth habit: Bushy, semi-woody sub-shrub producing sticky, aromatic leaves and dense clusters of inflated pouch flowers held above the foliage.
What fertiliser slipper flower actually wants — and why
Slipper Flower 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 slipper flower: 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 slipper flower, 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 slipper flower:
Apply a balanced liquid fertiliser every two weeks during the growing season; deadhead spent flowers regularly to prolong blooming. 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 slipper flower 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 slipper flower
Half strength is the safe default for slipper flower — 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 slipper flower first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the slipper flower watering schedule.
Signs you are over-feeding slipper flower
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for slipper flower:
- 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 slipper flower
- 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 slipper flower care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of slipper flower 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 slipper flower
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 slipper flower — frequently asked questions
What fertiliser does slipper flower 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. Slipper Flower 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 slipper flower?
Apply a balanced liquid fertiliser every two weeks during the growing season; deadhead spent flowers regularly to prolong blooming. Apply a balanced liquid fertiliser every two weeks during the growing season; deadhead spent flowers regularly to prolong blooming. 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 slipper flower?
Half strength is the safe default for slipper flower — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding slipper flower 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 slipper flower 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 slipper flower?
Flush the pot of slipper flower 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
- Slipper Flower care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water slipper flower — 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 columnea 'light prince'
- How to fertilise nematanthus 'tropicana'
- How to fertilise cape primrose 'bristol's party girl'
- All 10153 fertilising guides in the Growli library