Fertilising guide
How to fertilise Goldencup St. John's Wort (Hypericum patulum)— schedule & NPK
Also called Goldencup St. John's Wort, Patulum St. Johnswort, Japanese Hypericum.
More about goldencup st. john's wort
About Goldencup St. John's Wort
Hypericum patulum · also called Goldencup St. John's Wort, Patulum St. Johnswort · flowering
Hypericum patulum is a semi-evergreen East Asian shrub bearing large, saucer-shaped golden-yellow flowers from midsummer into autumn. More cold-sensitive than North American Hypericum species, it excels in mild temperate gardens as a border shrub or ground cover. The cultivar 'Hidcote' (often listed under H. 'Hidcote') is one of the most widely planted garden hypericums. Hardy zones 6–9.
Growth habit: Arching, semi-evergreen shrub with attractive golden-yellow exfoliating bark on older stems
Watch for — Aphid colonies: Soft new growth attracts aphids, which cause distorted shoot tips and sticky honeydew. Blast off with water, introduce ladybirds, or apply insecticidal soap. Avoid high-nitrogen feeding which promotes soft growth.
What fertiliser goldencup st. john's wort actually wants — and why
Goldencup St. John's Wort 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 goldencup st. john's wort: 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 goldencup st. john's wort, 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 goldencup st. john's wort:
Apply a balanced slow-release fertiliser (e.g. 5-10-5 or similar) in early spring as growth resumes. Avoid excess nitrogen. In fertile garden soils, annual feeding may not be needed. 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 goldencup st. john's wort 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 goldencup st. john's wort
Half strength is the safe default for goldencup st. john's wort — 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 goldencup st. john's wort first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the goldencup st. john's wort watering schedule.
Signs you are over-feeding goldencup st. john's wort
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for goldencup st. john's wort:
- 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 goldencup st. john's wort
- 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 goldencup st. john's wort care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of goldencup st. john's wort 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 goldencup st. john's wort
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 goldencup st. john's wort — frequently asked questions
What fertiliser does goldencup st. john's wort 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. Goldencup St. John's Wort 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 goldencup st. john's wort?
Apply a balanced slow-release fertiliser (e.g. 5-10-5 or similar) in early spring as growth resumes. Avoid excess nitrogen. In fertile garden soils, annual feeding may not be needed. Apply a balanced slow-release fertiliser (e.g. 5-10-5 or similar) in early spring as growth resumes. Avoid excess nitrogen. In fertile garden soils, annual feeding may not be needed. 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 goldencup st. john's wort?
Half strength is the safe default for goldencup st. john's wort — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding goldencup st. john's wort 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 goldencup st. john's wort 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 goldencup st. john's wort?
Flush the pot of goldencup st. john's wort 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
- Goldencup St. John's Wort care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water goldencup st. john's wort — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
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- All 8452 fertilising guides in the Growli library