Fertilising guide
How to fertilise Rough Chervil (Chaerophyllum temulum)— schedule & NPK
Also called Rough Chervil, Rough Cow Parsley.
More about rough chervil
About Rough Chervil
Chaerophyllum temulum · also called Rough Chervil, Rough Cow Parsley · flowering
Rough chervil is a native British and European biennial of hedgerows, roadsides, and woodland edges, belonging to the carrot family (Apiaceae). It produces flat-topped clusters of tiny white flowers from May to July atop stiff, purple-spotted, hairy stems that are distinctively swollen below each leaf node — a key identification feature that separates it from edible umbellifers. The single most important care fact is that it is toxic to people and animals if ingested: it must never be confused with edible parsley, chervil, or cow parsley. It is toxic and must be kept away from pets.
Growth habit: Upright biennial herb with distinctively hairy, purple-blotched stems swollen below the nodes; forms a basal rosette in year one and flowers in year two.
Watch for — Skin photosensitisation from sap: Furanocoumarins in the sap cause phototoxic burns on skin exposed to sunlight; wear gloves and long sleeves when handling and wash hands thoroughly afterwards.
What fertiliser rough chervil actually wants — and why
Rough Chervil 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 rough chervil: 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 rough chervil, 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 rough chervil:
No fertilising required — plants grow vigorously in naturally fertile hedgerow soils; added fertiliser may cause excessive leafy growth. 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 rough chervil 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 rough chervil
Half strength is the safe default for rough chervil — 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 rough chervil first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the rough chervil watering schedule.
Signs you are over-feeding rough chervil
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for rough chervil:
- 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 rough chervil
- 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 rough chervil care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of rough chervil 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 rough chervil
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 rough chervil — frequently asked questions
What fertiliser does rough chervil 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. Rough Chervil 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 rough chervil?
No fertilising required — plants grow vigorously in naturally fertile hedgerow soils; added fertiliser may cause excessive leafy growth. No fertilising required — plants grow vigorously in naturally fertile hedgerow soils; added fertiliser may cause excessive leafy growth. 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 rough chervil?
Half strength is the safe default for rough chervil — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding rough chervil 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 rough chervil 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 rough chervil?
Flush the pot of rough chervil 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
- Rough Chervil care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water rough chervil — 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 fiddle-leaf pelargonium
- How to fertilise hogweed
- How to fertilise mouse-ear hawkweed
- All 10153 fertilising guides in the Growli library