Fertilising guide
How to fertilise Formosa Lily (Lilium formosanum)— schedule & NPK
Also called Formosa Lily, Taiwan Lily.
More about formosa lily
About Formosa Lily
Lilium formosanum · also called Formosa Lily, Taiwan Lily · flowering
Formosa Lily is a tall, fragrant species lily native to Taiwan, producing trumpet-shaped white flowers with purple-flushed exteriors in late summer. It thrives in full sun with consistently moist, well-drained soil. Fast-growing from seed and naturalizes readily. Severely toxic to cats — even small exposures cause acute kidney failure.
Growth habit: Upright, clump-forming bulbous perennial with slender stems
What fertiliser formosa lily actually wants — and why
Formosa Lily feeds for next year, not this one — the critical window is after flowering, while the leaves are still green and recharging the bulb.
A low-nitrogen, potassium- and phosphorus-leaning bulb fertiliser (something like 5-10-10) or bonemeal at planting. High nitrogen grows floppy leaves and rots stored bulbs.
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 formosa 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 formosa 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 formosa lily:
Apply a balanced bulb fertiliser (e.g. 10-10-10) in early spring as shoots emerge, then switch to a low-nitrogen, high-potassium feed monthly through bud set. Cease feeding after flowering. The rhythm: a bulb feed at planting, a light feed as leaves emerge, and — most important — a potassium feed straight after flowering while the foliage is still green and feeding the bulb. Never cut the leaves off early.
The dormant-season rule matters more than the exact interval: skip feeding entirely when formosa 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 formosa lily
Use the bulb-feed label rate for formosa lily; the timing (post-bloom, leaves still green) does far more for next year's display than the concentration.
Feeding always goes onto already-damp soil, never dry roots — water formosa lily first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the formosa lily watering schedule.
Signs you are over-feeding formosa lily
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for formosa lily:
- Tall, floppy, soft leaves that flop over (too much nitrogen).
- Soft or rotting bulbs lifted at the end of the season.
- Lush foliage but few or poor flowers.
Signs you are under-feeding formosa lily
- Progressively fewer or smaller flowers year on year ("going blind").
- Small, weak bulbs and thin foliage.
- Bulbs that fail to come back at all after a few seasons.
If the symptoms point at watering, light or roots rather than nutrition, the full formosa lily care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Bulbs are not container-flushed like houseplants; the equivalent is not over-feeding and lifting/dividing congested clumps of formosa lily every few years so they are not competing for nutrients.
Organic vs synthetic feeds for formosa lily
Organic options
Bonemeal worked in at planting plus a mulch of garden compost or well-rotted leaf-mould is the traditional, reliable approach for formosa lily. UK: blood, fish & bone or Westland Bulb Food; US: Espoma Bulb-tone or bonemeal.
Synthetic / liquid feeds
A proprietary bulb fertiliser at planting and a high-potash liquid (tomato feed) after flowering — UK: Westland Bulb Food then Tomorite; US: Miracle-Gro Shake 'n Feed Bulb or a bloom booster post-flower.
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 formosa lily — frequently asked questions
What fertiliser does formosa lily need?
A low-nitrogen, potassium- and phosphorus-leaning bulb fertiliser (something like 5-10-10) or bonemeal at planting. High nitrogen grows floppy leaves and rots stored bulbs. Formosa Lily feeds for next year, not this one — the critical window is after flowering, while the leaves are still green and recharging the bulb.
How often should I feed formosa lily?
Apply a balanced bulb fertiliser (e.g. 10-10-10) in early spring as shoots emerge, then switch to a low-nitrogen, high-potassium feed monthly through bud set. Cease feeding after flowering. Apply a balanced bulb fertiliser (e.g. 10-10-10) in early spring as shoots emerge, then switch to a low-nitrogen, high-potassium feed monthly through bud set. Cease feeding after flowering. The rhythm: a bulb feed at planting, a light feed as leaves emerge, and — most important — a potassium feed straight after flowering while the foliage is still green and feeding the bulb. Never cut the leaves off early.
What strength of feed for formosa lily?
Use the bulb-feed label rate for formosa lily; the timing (post-bloom, leaves still green) does far more for next year's display than the concentration.
What does over-feeding formosa lily look like?
Tall, floppy, soft leaves that flop over (too much nitrogen). Soft or rotting bulbs lifted at the end of the season. Lush foliage but few or poor flowers. Cutting or tying off the leaves of formosa lily as soon as the flowers fade is the great bulb mistake — the bulb recharges through those leaves for weeks afterward, and removing them early means a weak or blind display next year.
Should I flush the soil of formosa lily?
Bulbs are not container-flushed like houseplants; the equivalent is not over-feeding and lifting/dividing congested clumps of formosa lily every few years so they are not competing for nutrients.
Keep reading
- Formosa Lily care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water formosa 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 athyrium filix-femina 'minutissimum'
- How to fertilise athyrium filix-femina 'frizelliae'
- How to fertilise athyrium otophorum
- All 6887 fertilising guides in the Growli library