Fertilising guide

How to fertilise Nun's Orchid (Phaius tankervilleae)— schedule & NPK

Also called Swamp Orchid, Veiled Nun Orchid.

More about nun's orchid

About Nun's Orchid

Phaius tankervilleae · also called Swamp Orchid, Veiled Nun Orchid · flowering

Phaius tankervilleae is a robust terrestrial orchid from Asia and the Pacific, sending up tall spikes of large, reddish-brown flowers backed with white and a rosy, trumpet-shaped lip. Unlike epiphytic orchids it grows in rich, moisture-retentive soil, wanting bright shade, warmth, steady water and feeding in growth, and is among the easiest orchids to grow as a houseplant or shaded garden plant.

Growth habit: Terrestrial sympodial orchid forming clumps of short, fleshy pseudobulbs at soil level, each bearing several large, broad, pleated leaves. Tall, erect flower spikes rise from the base in spring carrying many showy, fragrant trumpet-shaped blooms.

Watch for — Leaf scorch or yellowing: Direct sun burns the soft pleated leaves, while too little light yellows them and weakens spikes. Provide bright filtered light or light shade.

What fertiliser nun's orchid actually wants — and why

Nun's Orchid is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

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 nun's orchid: 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 nun's orchid, 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 nun's orchid:

Feed regularly during active growth and spiking with a balanced fertiliser at half strength every one to two weeks, as this vigorous terrestrial is a relatively heavy feeder. Reduce feeding after flowering and during the cooler, lower-light rest. The pattern that matters: feed little and often through active growth and budding — sparingly through the growing season — and ease right off during the rest period that triggers the next flush.

The dormant-season rule matters more than the exact interval: skip feeding entirely when nun's orchid 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 nun's orchid

Very dilute — quarter strength, the classic "weakly, weekly" approach for nun's orchid. These plants have fine roots that scorch easily and a steady trickle beats an occasional strong dose for flowering.

Feeding always goes onto already-damp soil, never dry roots — water nun's orchid first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the nun's orchid watering schedule.

Signs you are over-feeding nun's orchid

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for nun's orchid:

Lush green leaves but few or no flowers (too much nitrogen).
Brown, scorched leaf tips and edges — a classic fine-root burn.
White salt crust on the medium or pot, and stalled buds.
Bud blast: buds forming then shrivelling and dropping.

Signs you are under-feeding nun's orchid

Sparse or no flowering despite good light and the right season.
Smaller, paler new leaves and a generally weak, tired plant.
Flowers that are smaller or fade faster than they should.

If the symptoms point at watering, light or roots rather than nutrition, the full nun's orchid care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Specialist and bloom feeds leave salts that scorch fine roots — flush nun's orchid thoroughly with plain water until it runs clear every 4-6 weeks in the feeding season, and always between feeds for orchids.

Organic vs synthetic feeds for nun's orchid

Organic options

Gentler options exist: a dilute seaweed feed (mildly potassium-rich) or worm-casting tea. UK: Westland seaweed, or a dilute tomato feed like Tomorite for bud-formers; US: Espoma Orchid! / Violet! or Neptune's Harvest. Lower burn risk, slower response.

Synthetic / liquid feeds

A species-matched bloom feed at quarter strength — UK: Baby Bio Orchid / African Violet food, or a high-potash Tomorite/Phostrogen for budding bloomers; US: Miracle-Gro Orchid or Bloom Booster, Schultz African Violet.

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 nun's orchid — frequently asked questions

What fertiliser does nun's orchid need?

A higher-phosphorus "bloom" formula or a species-specific feed (orchid food, African violet food, or a tomato-style high-potash/phosphorus liquid). A high-nitrogen general feed gives you lush leaves and almost no flowers. Nun's Orchid is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

How often should I feed nun's orchid?

Feed regularly during active growth and spiking with a balanced fertiliser at half strength every one to two weeks, as this vigorous terrestrial is a relatively heavy feeder. Reduce feeding after flowering and during the cooler, lower-light rest. Feed regularly during active growth and spiking with a balanced fertiliser at half strength every one to two weeks, as this vigorous terrestrial is a relatively heavy feeder. Reduce feeding after flowering and during the cooler, lower-light rest. The pattern that matters: feed little and often through active growth and budding — sparingly through the growing season — and ease right off during the rest period that triggers the next flush.

What strength of feed for nun's orchid?

What does over-feeding nun's orchid look like?

Lush green leaves but few or no flowers (too much nitrogen). Brown, scorched leaf tips and edges — a classic fine-root burn. White salt crust on the medium or pot, and stalled buds. Bud blast: buds forming then shrivelling and dropping. Using an ordinary high-nitrogen houseplant feed on nun's orchid is the headline mistake — you get a healthy-looking plant that simply refuses to bloom. The second is feeding through the rest period and breaking the dormancy cue it needs to set buds.

Should I flush the soil of nun's orchid?