Fertilising guide

How to fertilise Hardy Geranium 'Rozanne' (Geranium 'Rozanne')— schedule & NPK

Also called Rozanne cranesbill, Gerwat Rozanne.

More about hardy geranium 'rozanne'

About Hardy Geranium 'Rozanne'

Geranium 'Rozanne' · also called Rozanne cranesbill, Gerwat Rozanne · flowering

Geranium 'Rozanne' is an award-winning hardy cranesbill famous for an exceptionally long season of large violet-blue, white-eyed flowers from early summer to autumn frost. It forms a spreading mound of marbled green leaves, weaves through borders and containers, and asks only for sun to part shade and decent drainage. A near-effortless, sterile, ground-covering perennial.

Growth habit: Mound-forming, sprawling herbaceous perennial that spreads by trailing stems rather than aggressive runners, weaving 60-90 cm wide through neighbouring plants. Sterile, so it flowers continuously without setting seed.

What fertiliser hardy geranium 'rozanne' actually wants — and why

Hardy Geranium 'Rozanne' 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 hardy geranium 'rozanne': 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 hardy geranium 'rozanne', 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 hardy geranium 'rozanne':

Low feed needs. A spring mulch of compost or a single balanced slow-release feed at growth start is enough for borders; container plants benefit from monthly liquid feed in the growing season. Excess nitrogen produces leaf at the expense of flower. For a hungry bloomer that means feeding regularly — monthly — 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 hardy geranium 'rozanne' 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 hardy geranium 'rozanne'

Follow the flowering-feed label rate for hardy geranium 'rozanne', 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 hardy geranium 'rozanne' first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the hardy geranium 'rozanne' watering schedule.

Signs you are over-feeding hardy geranium 'rozanne'

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for hardy geranium 'rozanne':

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 hardy geranium 'rozanne'

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 hardy geranium 'rozanne' care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Container-grown hardy geranium 'rozanne' 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 hardy geranium 'rozanne'

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 hardy geranium 'rozanne' — frequently asked questions

What fertiliser does hardy geranium 'rozanne' 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. Hardy Geranium 'Rozanne' 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 hardy geranium 'rozanne'?

Low feed needs. A spring mulch of compost or a single balanced slow-release feed at growth start is enough for borders; container plants benefit from monthly liquid feed in the growing season. Excess nitrogen produces leaf at the expense of flower. Low feed needs. A spring mulch of compost or a single balanced slow-release feed at growth start is enough for borders; container plants benefit from monthly liquid feed in the growing season. Excess nitrogen produces leaf at the expense of flower. For a hungry bloomer that means feeding regularly — monthly — right through flowering across the main season (spring through early autumn), tapering as blooming ends.

What strength of feed for hardy geranium 'rozanne'?

What does over-feeding hardy geranium 'rozanne' 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 hardy geranium 'rozanne' 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 hardy geranium 'rozanne'?