Fertilising guide
How to fertilise False shamrock (Oxalis triangularis)— schedule & NPK
Also called purple shamrock, love plant, wood sorrel (purple).
About False shamrock
Oxalis triangularis · also called purple shamrock, love plant · flowering
False shamrock is a Brazilian tuberous perennial with deep purple triangular leaves that fold up at night, and small pink flowers. Easy and forgiving but mildly toxic to pets due to oxalic acid. Tubers cycle through dormancy.
Oxalis triangularis, a tuberous wood-sorrel native to Brazil, grown for its deep-purple triangular trifoliate leaves that arise from small scaly underground tubers.
Feed a dilute balanced fertiliser only during active growth; stop entirely once it enters its natural rest period.
Growth habit: Tuberous mounding perennial
Sources: libguides.nybg.org, aspca.org
What fertiliser false shamrock actually wants — and why
False shamrock 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 false shamrock: 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 false shamrock, 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 false shamrock:
Half-strength balanced feed monthly during growth. Treat that as monthly 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 false shamrock 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 false shamrock
Half strength is the safe default for false shamrock — 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 false shamrock first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the false shamrock watering schedule.
Signs you are over-feeding false shamrock
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for false shamrock:
- 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 false shamrock
- 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 false shamrock care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of false shamrock 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 false shamrock
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 false shamrock — frequently asked questions
What fertiliser does false shamrock 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. False shamrock 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 false shamrock?
Half-strength balanced feed monthly during growth. Half-strength balanced feed monthly during growth. Treat that as monthly 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 false shamrock?
Half strength is the safe default for false shamrock — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding false shamrock 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 false shamrock 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 false shamrock?
Flush the pot of false shamrock 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
- False shamrock care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water false shamrock — 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 200 fertilising guides in the Growli library