Fertilising guide
How to fertilise Broad-Petalled Cranesbill (Geranium platypetalum)— schedule & NPK
Also called Broad-Petalled Cranesbill, Broad-Petalled Geranium, Hardy Cranesbill.
More about broad-petalled cranesbill
About Broad-Petalled Cranesbill
Geranium platypetalum · also called Broad-Petalled Cranesbill, Broad-Petalled Geranium · flowering
Geranium platypetalum is a robust herbaceous perennial native to the Caucasus region and northern Iran, forming dense mounds of large, deeply lobed, softly hairy leaves. It thrives in moderately fertile, well-drained soil in full sun to partial shade and is prized for its violet-blue flowers with darker veining produced in early to mid-summer. The single most important care task is cutting back hard after flowering to encourage a flush of fresh foliage. According to ASPCA guidance, true Geranium species (cranesbills) are non-toxic to cats and dogs.
Growth habit: Clump-forming deciduous herbaceous perennial that dies back to the crown in winter.
Watch for — Vine weevil: C-shaped grubs feed on roots in late summer to autumn, causing plants to wilt and collapse; treat container-grown plants with nematodes (Steinernema kraussei) from August to October when soil temperature is above 5°C.
What fertiliser broad-petalled cranesbill actually wants — and why
Broad-Petalled Cranesbill flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.
Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency.
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 broad-petalled cranesbill: 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 broad-petalled cranesbill, 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 broad-petalled cranesbill:
Apply a balanced slow-release granular fertiliser in early spring; avoid high-nitrogen feeds that promote leafy growth at the expense of flowers. In practice: no routine feeding at all for broad-petalled cranesbill — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.
The dormant-season rule matters more than the exact interval: skip feeding entirely when broad-petalled cranesbill 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 broad-petalled cranesbill
None is the correct answer for broad-petalled cranesbill. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.
Feeding always goes onto already-damp soil, never dry roots — water broad-petalled cranesbill first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the broad-petalled cranesbill watering schedule.
Signs you are over-feeding broad-petalled cranesbill
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for broad-petalled cranesbill:
- Abundant leafy growth and very few flowers (the classic over-rich symptom).
- Soft, floppy stems and a sprawling, leafy habit.
- Scorched edges and salt crust if it has been fed in a container.
Signs you are under-feeding broad-petalled cranesbill
- Effectively never an issue — these plants flower on poverty.
- Only on genuinely dead soil: weak, thin growth and few blooms.
- A short-lived plant in completely spent container compost.
If the symptoms point at watering, light or roots rather than nutrition, the full broad-petalled cranesbill care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
If broad-petalled cranesbill has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.
Organic vs synthetic feeds for broad-petalled cranesbill
Organic options
A thin compost mulch for soil structure is the absolute most; mostly, give it nothing. UK/US: leave it lean — no manure, no liquid feed. Poor soil is the active ingredient here.
Synthetic / liquid feeds
None. Synthetic feeds, particularly anything with appreciable nitrogen, directly suppress flowering in broad-petalled cranesbill.
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 broad-petalled cranesbill — frequently asked questions
What fertiliser does broad-petalled cranesbill need?
Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency. Broad-Petalled Cranesbill flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.
How often should I feed broad-petalled cranesbill?
Apply a balanced slow-release granular fertiliser in early spring; avoid high-nitrogen feeds that promote leafy growth at the expense of flowers. Apply a balanced slow-release granular fertiliser in early spring; avoid high-nitrogen feeds that promote leafy growth at the expense of flowers. In practice: no routine feeding at all for broad-petalled cranesbill — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.
What strength of feed for broad-petalled cranesbill?
None is the correct answer for broad-petalled cranesbill. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.
What does over-feeding broad-petalled cranesbill look like?
Abundant leafy growth and very few flowers (the classic over-rich symptom). Soft, floppy stems and a sprawling, leafy habit. Scorched edges and salt crust if it has been fed in a container. Feeding broad-petalled cranesbill at all — especially "to help it flower" — is the defining mistake. Rich soil gives you a big green plant and almost no blooms; restraint is what produces the flowers.
Should I flush the soil of broad-petalled cranesbill?
If broad-petalled cranesbill has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.
Keep reading
- Broad-Petalled Cranesbill care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water broad-petalled cranesbill — 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 two-leaf squill
- How to fertilise cuban lily
- How to fertilise common snowdrop
- All 10153 fertilising guides in the Growli library