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How to feed a cactus

Updated: October 2026

The bottle is already on the shelf, the days are longer, and you are not sure whether this week is a feeding week. How to feed a cactus in a UK home is a calendar plus one physical rule: the compost should already be moist, and a resting desert cactus should not be fed just because the cap is clean. This page is for a desert cactus or an ordinary succulent on a windowsill. A Christmas cactus is a different plant, with a different rest. Product ranks stay on the [cactus fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/cactus-fertiliser). Products Compared used Royal Horticultural Society and BBC Gardeners’ World guidance, read with the listing fields on 19 October 2026, and did not run a feeding trial.

The bottle is already on the shelf, the days are longer, and you are not sure whether this week is a feeding week.

Our top picks

Baby Bio Baby Bio cactus food, 175 ml

Best overall

Baby Bio Baby Bio cactus food, 175 ml
9.4/10about £3.99
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FITO FITO cactus drip feeder, 32 ml

Best value

FITO FITO cactus drip feeder, 32 ml
8.3/10about £3.61
View offer
UK GROW UK GROW cactus foliar spray, 1 litre

Alternative

UK GROW UK GROW cactus foliar spray, 1 litre
7.1/10about £14.99
View offer
On this page
  1. 1.The UK months
  2. 2.How the feed goes on
  3. 3.When the label and the RHS disagree
  4. 4.Stop points

The UK months

Feed a growing desert cactus from April to September. The RHS says once a month, with a high-potassium liquid or a specialist cactus feed, and a winter rest from November to the beginning of March. In December and January the compost stays barely moist, with no feeding. A bright week in February does not cancel the rest. BBC Gardeners’ World says every two weeks in spring and summer on its feeding page, and every three months on its succulent-care page.

How the feed goes on

Do not put fertiliser on dry compost. The RHS says fertiliser on dry soil can burn roots. Wet the pot, let it drain, then add a dilute feed. A dust-dry pot gets plain water first, and feed at the next watering. Empty the saucer. FITO claims up to 15 days from one push-in. That can cover a holiday in July. It is not April to September. UK GROW and Black Gold are foliar. Plantsmith says not to mist desert cacti. Keep a root drench off the ribs and out of the crown. The format choice is on the cactus fertiliser liquid or granules page.
Baby Bio Baby Bio cactus food, 175 ml

Testsieger

Baby Bio Baby Bio cactus food, 175 ml
9.4/10about £3.99
View offer

When the label and the RHS disagree

Monthly from the RHS and Thompson & Morgan, fortnightly from the BBC feeding page, and every three months from the BBC succulent page cannot be stacked. Use once a month while a desert cactus is growing, and nothing in the winter rest. More feed will not replace light, and it makes a wet pot worse. According to the manufacturer, Growth Technology says occasionally in winter. That conflicts with the RHS rest, so stop. The Garden Patch mentions a half-strength tomato feed from April to September only, as a rule of thumb, not a dose for a named bottle. If you are still choosing, the checks are on the cactus fertiliser buying guide.

Stop points

Stop when the compost is dry, when the month sits outside April to September, or when the plant is a Christmas cactus on a desert timetable. Take a 15-day drip out when the rest starts. Skip a spray into a rosette. If someone swallows the concentrate, contact NHS 111 or the emergency services. None of the kept listings states a pesticide. A soft plant after a heavy feed is a reason to flush with plain water and stop. Schlumbergera needs a different winter. Use the Christmas cactus fertiliser page before you copy this rest.

Common questions

How often should you feed an indoor cactus in the UK?
For a desert cactus, the RHS says once a month from April to September. BBC Gardeners’ World says every two weeks in spring and summer on its feeding page, and every three months on its succulent-care page. Those are not one rule. Use the monthly interval unless your label gives a cactus-specific gap that still stops for winter. Feeding more often does not repair a plant that is too dark or sitting in wet compost. If the sources disagree, the quieter calendar is the one to follow for a plant you cannot replace easily.
Which months do you stop?
Stop from November to the beginning of March for most desert cacti. The RHS calls that the rest, with very little water and no feed. Its December and January houseplant notes repeat the point: barely moist compost, and no feeding. If growth has already stopped in October, do not open a new round because the bottle is handy. Christmas cacti are not on this stop list. They have their own rests, and drying them like a desert cactus is a different mistake.
Do you feed a dry pot?
Do not feed dry compost. The RHS says fertiliser on dry soil can burn roots. Water when the surface is dry, let the pot drain, and feed only once the compost is moist. A pot that has been dust-dry for a fortnight gets plain water first. Feed at the following watering if you are still inside April to September. The same warning covers granules and liquids. A prill on a dry surface is still fertiliser next to the roots.
Do you leave water in the saucer?
Empty the saucer. The RHS tells you to empty excess water after you water cacti in spring and summer. A saucer of dilute feed is then drawn back into the compost, which concentrates salts around the roots. Tip it away rather than leaving the pot standing in the runoff. That matters in a plastic pot with nowhere for water to escape, and it still matters in a clay pot if the saucer is full. The feed belongs in a brief watering, not in a permanent puddle.
Is a tomato feed safe, and at what strength?
The Garden Patch suggests a half-strength tomato feed as a stand-in for a specialist cactus fertiliser, monthly from April to September and not from October to March. That is a UK grower’s rule of thumb, not a dose printed on the amazon.co.uk listings in this comparison. Do not copy a greenhouse tomato rate onto a cactus, and do not treat half-strength as the instruction for Baby Bio or any other named bottle. If you already have a specialist feed with a ratio, use that ratio.

Related pages

Cactus fertiliser comparison

Christmas cactus fertiliser

Cactus fertiliser buying guide

Liquid or granules

Best cactus fertiliser: a conditional windowsill pick

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings captured on 19 October 2026. An NPK on a retailer page is not the amazon listing analysis. A pet-safety bullet is a listing claim. There is no laboratory test in this comparison.

  1. RHS, How to grow cacti and succulents (retrieved 19 October 2026)
  2. RHS, How to feed plants (retrieved 19 October 2026)
  3. RHS, How to grow Christmas cactus (retrieved 19 October 2026)
  4. RHS, Fertiliser labels explained (retrieved 19 October 2026)
  5. BCSS, The growing year (retrieved 19 October 2026)
  6. GOV.UK, Manufacturing and marketing fertilisers (retrieved 19 October 2026)
  7. The Fertilisers Regulations 1991 (retrieved 19 October 2026)
  8. ASDA, Baby Bio Cactus Food 175 ml (retrieved 19 October 2026)
  9. Ideal Home, Christmas cactus and sugar water (retrieved 19 October 2026)