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How to feed geraniums in spring, summer and winter

Updated: October 2026

The bottle is already on the bench, or you are about to mix one, and the question is when a UK pelargonium actually wants it. How to feed geraniums means the tender plants in pots, not a hardy cranesbill that is fine in the border. Feed moist compost, shift toward potassium once flowers form, and stop when the plant is dried off for winter. The dose is the label. Several Cultivers liquids in the [geranium fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/geranium-fertiliser) do not print a dilution in the product data, so this page will not invent a millilitre figure. A qualifying purchase can earn a commission at no extra cost to you.

The bottle is already on the bench, or you are about to mix one, and the question is when a UK pelargonium actually wants it.

Our top picks

Cultivers Cultivers organic geranium and flowering plant fertiliser 250 g

Best overall

Cultivers Cultivers organic geranium and flowering plant fertiliser 250 g
10.0/10about £11.62
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Fertiligène Fertiligène Osmocote Max geranium fertiliser 700 g

Alternative

Fertiligène Fertiligène Osmocote Max geranium fertiliser 700 g
9.4/10about £23.00
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Cultivers Cultivers organic liquid geranium fertiliser 1 litre

Alternative

Cultivers Cultivers organic liquid geranium fertiliser 1 litre
7.8/10about £15.86
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On this page
  1. 1.Before you mix anything
  2. 2.Spring, then flowering
  3. 3.Autumn, winter, and dried-off plants
  4. 4.Liquid cap or granule dose

Before you mix anything

Watering comes before the cap. The RHS wants pelargonium compost moist, not sodden and not bone dry. A yellow plant in a wet pot is a drainage problem first. If the saucer is full after rain, tip it out before you feed. Granules belong on the compost, not on wet leaves. The Osmocote listing says spread, scratch in and water. Outdoor plants usually stay inside until the end of May in much of the UK, and until early or mid June in Scotland. If you are not sure the plant is a pelargonium, settle that on pelargonium or hardy geranium before you open the bottle.

Spring, then flowering

In spring the RHS pelargonium guide says a balanced liquid every 10 to 14 days. Once flowers form, switch to a high-potassium fertiliser, such as tomato feed, every fortnight. Cultivers liquids state NPK 4-1-7. That leans toward potassium next to the 8-1-5 packs, and it is not an RHS recipe. The National Collection of Pelargonium describes spring feed as nitrogen-rich, then potassium every two weeks. This page follows the RHS growing guide where the two differ. In the Amazon reviews a Belgian comment on the 1 kg pack said monthly on the notice and twice a month in practice. That is not a liquid rate.
Cultivers Cultivers organic geranium and flowering plant fertiliser 250 g

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Cultivers Cultivers organic geranium and flowering plant fertiliser 250 g
10.0/10about £11.62
View offer

Autumn, winter, and dried-off plants

A general RHS page says not to feed after September. The pelargonium guide is more specific. At about 7 to 10 °C, a plant still growing can take a monthly feed. If you dry it off, stop. The November note says cut back, water less, do not feed, and keep a dormant plant near 10 °C. A plant still flowering in a heated porch is not a crown stored dry. Monthly feed applies only while it is in growth. A hardy cranesbill in the border is outside this calendar.

Liquid cap or granule dose

Cultivers liquids do not print a dilution in the product data. The label is the dose. Do not copy a millilitre figure from another brand. The Osmocote Max tub prints 3 to 6 g per plant in a pot. The 3.5 handfuls per square metre line is for the ground, not a basket. The listing window is February to June, with a one-year claim. That claim does not replace the RHS fortnightly liquid. Use one method, not both at full strength. The tub has no NPK in the product data. Pack choice is on the geranium fertiliser buying guide. If a child or a pet swallows concentrate, contact NHS 111.

Common questions

How often in summer?
Once flowers have formed, the RHS pelargonium guide says a high-potassium feed every fortnight. Spring, before that flush, is a balanced liquid every 10 to 14 days. Other brands tell you to feed at every watering. That is their habit, not this calendar. Your label can be stricter than the fortnight. It should not be ignored because a forum used a different bottle.
When do I switch to a high-potassium feed?
Switch when flowers form, not on a fixed date in May. The RHS names a high-potassium fertiliser such as tomato feed for that stage, fortnightly through summer. A 4-1-7 liquid is the potassium-leaning analysis in this Cultivers set. It is still not a substitute for reading the dilution on the carton.
Is tomato feed allowed?
Yes, as the pattern the RHS describes. A tomato feed is a high-potassium liquid you can use on flowering pelargoniums. It is not one of the eight ASINs here, and Levington Tomorite is only an illustration on the RHS fertilisers page. Follow that bottle's rate if that is the bottle you bought.
When do I stop for winter?
Stop if you dry the plant off. If you keep it growing at about 7 to 10 °C, the pelargonium guide allows a monthly feed. A dormant plant near 10 °C is not fed, which matches the RHS November note. Do not use the general nothing-after-September line to cancel that monthly feed for a plant that is still growing in the warm.
What if the plant is yellow and wet?
Do not feed it harder. Empty the saucer, let the compost become moist rather than sodden, and check that the pot can drain. Yellow leaves on a wet pelargonium are often roots in stale water. Fertiliser on top of that is a second stress, not a cure. Feed again only when the compost is merely moist.
Where do I put granules?
On the compost surface, at the gram dose the pack prints, then scratch them in lightly and water if the instructions say so. Keep them off leaves. The Osmocote pot figure in this set is 3 to 6 g per plant. The handful rate for open ground is a different job and the wrong measure for a 20 cm pot.
Does the Osmocote tub replace the fortnightly liquid?
Only if you are choosing the listing's once-a-year claim instead of the RHS liquid calendar. The tub's stated window is February to June, and the product data has no NPK. It does not become a fortnightly potassium feed by another name. Use one method with a clear dose, not both at full rate.

Related pages

Geranium fertiliser for pots and baskets

Geranium fertiliser

Best geranium fertiliser for pots, once or baskets

Geranium fertiliser buying guide: form, NPK and pack

Pelargonium or hardy geranium: which plant to feed

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the eight amazon.co.uk listings captured on 19 October 2026. Organic, vegan and pet-safety lines are listing claims. The one-year granule line is the listing's claim, not a laboratory result. French, Spanish and Belgian reviews are not British comments.

  1. RHS, How to grow pelargoniums (retrieved 19 October 2026)
  2. RHS, How to grow geraniums (retrieved 19 October 2026)
  3. RHS, How to feed plants (retrieved 19 October 2026)
  4. RHS, Fertiliser labels explained (retrieved 19 October 2026)
  5. GOV.UK, Manufacturing and marketing fertilisers (retrieved 19 October 2026)
  6. legislation.gov.uk, Regulation (EC) No 2003/2003 Title I (retrieved 19 October 2026)
  7. RHS, Storing and disposing of chemicals safely (retrieved 19 October 2026)
  8. amazon.co.uk listings for the eight compared packs (retrieved 19 October 2026)