Fertilising guide
How to fertilise Geranium psilostemon (Geranium psilostemon)— schedule & NPK
Also called Armenian cranesbill.
More about geranium psilostemon
About Geranium psilostemon
Geranium psilostemon · also called Armenian cranesbill · flowering
Geranium psilostemon, Armenian cranesbill, is a large, statuesque hardy geranium making a bold clump of deeply lobed leaves topped in summer by vivid magenta flowers with striking black centres and veins. It needs space, supports itself fairly well, and brings electric colour to mixed borders. Foliage frequently turns red and orange in autumn.
Growth habit: Large, vigorous clump-forming herbaceous perennial with tall, branching, leafy stems rising from a basal mound, producing an airy haze of bright flowers above the foliage.
What fertiliser geranium psilostemon actually wants — and why
Geranium psilostemon is a heavy-blooming flower with a big appetite — a regular high-potash feed through the season is what drives a long, dense display.
A high-potassium ("high-potash") flowering feed — tomato-style or a dedicated bloom/rose feed. Potassium powers flowering; a high-nitrogen feed gives you a leafy plant with disappointing bloom.
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 geranium psilostemon: 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 geranium psilostemon, 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 geranium psilostemon:
Moderate feeder for a cranesbill given its size. A spring mulch of compost or a balanced slow-release feed at growth start supports the large leafy clump; avoid excess nitrogen, which encourages flop over flower. For a hungry bloomer that means feeding regularly — sparingly through the growing season — right through flowering across the main season (spring through early autumn), tapering as blooming ends.
The dormant-season rule matters more than the exact interval: skip feeding entirely when geranium psilostemon 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 geranium psilostemon
Follow the flowering-feed label rate for geranium psilostemon, or half strength if feeding very frequently. These plants genuinely use the nutrients — under-feeding shows up fast as a thin display.
Feeding always goes onto already-damp soil, never dry roots — water geranium psilostemon first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the geranium psilostemon watering schedule.
Signs you are over-feeding geranium psilostemon
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for geranium psilostemon:
- Lots of lush leaves but few flowers (too much nitrogen).
- Scorched leaf edges and salt crust from too-strong or too-frequent feeds.
- Soft, sappy growth prone to aphids and mildew.
Signs you are under-feeding geranium psilostemon
- Sparse, small, short-lived flowers and pale foliage.
- A tired plant that stops blooming early in the season.
- Weak growth and poor repeat-flowering after the first flush.
If the symptoms point at watering, light or roots rather than nutrition, the full geranium psilostemon care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Container-grown geranium psilostemon accumulates feed salts fast with frequent feeding — water until it drains each time and flush pots with plain water every few weeks to prevent scorch.
Organic vs synthetic feeds for geranium psilostemon
Organic options
A liquid comfrey or seaweed feed (naturally potassium-rich) plus compost or well-rotted manure as a mulch. UK: comfrey feed, organic Tomorite, or rose feed; US: Espoma Rose-tone or Neptune's Harvest. Feeds and improves soil.
Synthetic / liquid feeds
A high-potash flowering feed on a regular cadence — UK: Tomorite (Levington), Phostrogen or a specialist rose feed; US: Miracle-Gro Bloom Booster or a rose food. Fast, reliable bloom response.
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 geranium psilostemon — frequently asked questions
What fertiliser does geranium psilostemon need?
A high-potassium ("high-potash") flowering feed — tomato-style or a dedicated bloom/rose feed. Potassium powers flowering; a high-nitrogen feed gives you a leafy plant with disappointing bloom. Geranium psilostemon is a heavy-blooming flower with a big appetite — a regular high-potash feed through the season is what drives a long, dense display.
How often should I feed geranium psilostemon?
Moderate feeder for a cranesbill given its size. A spring mulch of compost or a balanced slow-release feed at growth start supports the large leafy clump; avoid excess nitrogen, which encourages flop over flower. Moderate feeder for a cranesbill given its size. A spring mulch of compost or a balanced slow-release feed at growth start supports the large leafy clump; avoid excess nitrogen, which encourages flop over flower. For a hungry bloomer that means feeding regularly — sparingly through the growing season — right through flowering across the main season (spring through early autumn), tapering as blooming ends.
What strength of feed for geranium psilostemon?
Follow the flowering-feed label rate for geranium psilostemon, or half strength if feeding very frequently. These plants genuinely use the nutrients — under-feeding shows up fast as a thin display.
What does over-feeding geranium psilostemon look like?
Lots of lush leaves but few flowers (too much nitrogen). Scorched leaf edges and salt crust from too-strong or too-frequent feeds. Soft, sappy growth prone to aphids and mildew. Using a high-nitrogen general feed on geranium psilostemon is the headline mistake — you grow a big leafy plant with few flowers. The second is simply under-feeding a genuinely hungry bloomer and getting a sparse, short display.
Should I flush the soil of geranium psilostemon?
Container-grown geranium psilostemon accumulates feed salts fast with frequent feeding — water until it drains each time and flush pots with plain water every few weeks to prevent scorch.
Keep reading
- Geranium psilostemon care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water geranium psilostemon — 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 2464 fertilising guides in the Growli library