Fertilising guide
How to fertilise Common hollyhock (Alcea rosea)— schedule & NPK
Also called Common hollyhock, Garden hollyhock, Single hollyhock.
More about common hollyhock
About Common hollyhock
Alcea rosea · also called Common hollyhock, Garden hollyhock · flowering
Common hollyhock is a stately cottage-garden biennial or short-lived perennial producing towering spikes of saucer-shaped flowers in white, pink, red, purple, and near-black. Plants grow 1.5–3 m tall and self-seed freely. They thrive in full sun with well-drained soil and are a classic back-of-border plant beloved by pollinators.
Growth habit: Erect, unbranched to lightly branched biennial or short-lived perennial; forms a basal rosette in year one, then bolts to produce a towering spike in year two
What fertiliser common hollyhock actually wants — and why
Common hollyhock 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 common hollyhock: 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 common hollyhock, 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 common hollyhock:
Apply a balanced granular fertiliser (e.g. 10-10-10) in spring as growth resumes, then switch to a low-nitrogen, higher-potash feed (e.g. tomato fertiliser) once flower buds form to maximise bloom rather than foliage. A single top-dress of well-rotted compost in autumn supports self-sown seedlings. 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 common hollyhock 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 common hollyhock
Half strength is the safe default for common hollyhock — 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 common hollyhock first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the common hollyhock watering schedule.
Signs you are over-feeding common hollyhock
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for common hollyhock:
- 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 common hollyhock
- 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 common hollyhock care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of common hollyhock 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 common hollyhock
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 common hollyhock — frequently asked questions
What fertiliser does common hollyhock 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. Common hollyhock 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 common hollyhock?
Apply a balanced granular fertiliser (e.g. 10-10-10) in spring as growth resumes, then switch to a low-nitrogen, higher-potash feed (e.g. tomato fertiliser) once flower buds form to maximise bloom rather than foliage. A single top-dress of well-rotted compost in autumn supports self-sown seedlings. Apply a balanced granular fertiliser (e.g. 10-10-10) in spring as growth resumes, then switch to a low-nitrogen, higher-potash feed (e.g. tomato fertiliser) once flower buds form to maximise bloom rather than foliage. A single top-dress of well-rotted compost in autumn supports self-sown seedlings. 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 common hollyhock?
Half strength is the safe default for common hollyhock — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding common hollyhock 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 common hollyhock 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 common hollyhock?
Flush the pot of common hollyhock 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
- Common hollyhock care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water common hollyhock — 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 creeping phlox
- How to fertilise wild blue phlox
- How to fertilise creeping woodland phlox
- All 6887 fertilising guides in the Growli library