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How to fertilise a bonsai without drowning the pot

Updated: October 2026

The bottle is already on the side, and the pot on the kitchen table holds far less than a litre. The useful question is not how much feed you can tip in, but when a growing tree can take the label strength, and when you should put the bottle down. This is how to fertilise a bonsai with the products in our set: a measured liquid, or pellets that print no gram dose. The [bonsai fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/bonsai-fertiliser) is where the packs are listed. What to buy, if you do not own one yet, is the [buying guide](/hub/fertiliser-soil-and-bark-mulch/bonsai-fertiliser/sub/bonsai-fertiliser-buying-guide). Links to Amazon can earn us a commission at no extra cost to you.

The bottle is already on the side, and the pot on the kitchen table holds far less than a litre.

Our top picks

Biogold BioGold 900 g

Best overall

Biogold BioGold 900 g
7.6/10about £34.99
View offer
Growth Technology Ltd Bonsai Focus 100 ml

Rank 2

Growth Technology Ltd Bonsai Focus 100 ml
8.4/10about £3.35
View offer
Chrysal Liquid Bonsai Feed 250 ml

Preis-Tipp

Chrysal Liquid Bonsai Feed 250 ml
8.1/10about £9.95
View offer
On this page
  1. 1.Feed only a tree that is growing
  2. 2.Liquids: same strength, less water
  3. 3.Pellets when the bag prints no dose
  4. 4.A UK season, outdoors first

Feed only a tree that is growing

A bonsai in a small pot runs out of nutrients because there is almost no compost, which is the Royal Horticultural Society’s reason for feeding in the growing season. Feed a tree that is in growth, with moist compost, at the strength on the label. Do not feed a tree that is bone dry, newly repotted, or clearly sick. The Federation of British Bonsai Societies says lack of water is the usual failure, and that excess feed can damage the tree. Soak a dry pot with plain water first. FOBBS says do not feed for at least six weeks after repotting. If you are new to this, use that longer wait unless the label in your hand says otherwise.

Liquids: same strength, less water

Mix at the label ratio, then give the pot only the volume it will hold. A smaller pot needs less liquid at the same dilution. It does not need a thicker mix. Bonsai Focus prints the clearest figure in this set: 5 ml in 1 litre of clean water, also written as 1:200. The strength stays 5 ml per litre. Do not double the concentrate because the pot is small. Focus’s listing says March until August, with occasional use in winter. The 250 ml liquid prints 4-6-6 and a scraped field says 1:1. Do not use 1:1. The format choice is on liquid vs pellet bonsai fertiliser. Bonsai Focus is classed as an eye irritant. Keep it away from children, and do not decant it into a drinks bottle. The poisons line on the safety data sheet is 0344 892 0111.
Biogold BioGold 900 g

Testsieger

Biogold BioGold 900 g
7.6/10about £34.99
View offer

Pellets when the bag prints no dose

BioGold and Naruko do not give a gram dose or a cakes-per-pot count in the listings. You cannot invent four pieces on a 15 cm pot and call it the label. A reviewer’s couple of rocks for a month or two is that person’s habit. Place the pieces on the soil, water as you normally would, and stop adding more because the first ones are still sitting there. Crushing BioGold into a tea, which one reviewer found difficult, is not the method on the listing. The listing method is to leave the pieces and water. Naruko’s reviews return to mould within a day or two. That is not an instruction to pile on a second dose. If you overdid a liquid, flush the pot with plain water until it runs from the drainage holes, then pause the feed.

A UK season, outdoors first

For a hardy tree that lives outside, think March to September, then ease off. Focus’s listing window is March until August, with only occasional winter use. FOBBS says feed healthy trees every two weeks in the growing season, and by September prefer a liquid and little nitrogen. The RHS says not to push high nitrogen after September, because you do not want soft growth going into cold weather. Do not skip the soak on a dry day in July and then pour feed onto dust. Outdoor winter is a stop for a juniper or a pine that is static. According to the manufacturer, Growth Technology’s indoor leaflet says avoid November to January for Bonsai Focus even indoors. The detail for a ficus is on indoor bonsai fertiliser. If concentrate has gone in an eye, use NHS 111 and 0344 892 0111.

Common questions

How often should I feed in a British summer?
On a healthy outdoor tree that is growing, FOBBS and the RHS describe a low-dose liquid about every two weeks through the growing season. Follow the bottle if it states a gap. Focus’s listing points at March to August. A missed Sunday is safer than a double dose the next week.
How long do I wait after repotting?
The UK sources do not agree. Deepcut says three to four weeks. The Growth Technology indoor leaflet says four weeks before Bonsai Focus. FOBBS says at least six weeks. For a first tree, wait six weeks unless your label is explicit. Feeding in that fortnight does not speed the repair.
My pot only holds a cup of water. Do I use less water or a thicker mix?
Use less volume at the same strength. Focus is 5 ml per litre, so a 250 ml cup takes about 1.25 ml, not 5 ml poured into a puddle. The 5 ml figure is the strength, not 5 ml in every pot regardless of size. A thicker mix in a tiny pot is how you burn roots.
Can I feed in winter?
Not as a summer routine. Outdoor hardy trees should be on little or no nitrogen by September, and static in winter. Focus allows occasional winter use on its listing, which is not a weekly feed. Indoor trees have a separate pause: the Growth Technology leaflet says avoid November to January. That retailer frequency is not the amazon label.
The pellets have no dose. What then?
Do not invent one. The BioGold and Naruko listings in this set do not print grams per pot. Put a few pieces on the soil, water normally, and leave them. Do not crush them into a liquid because a bottle feels more precise. If the Naruko surface moulds within a day, that matches the review pattern. Do not correct it by adding more cakes.

Related pages

Bonsai fertiliser

Best bonsai feed matched to the tree you actually have

Best bonsai fertiliser UK: what to check before you buy

Indoor bonsai fertiliser for a ficus that stays indoors

Liquid vs pellet bonsai fertiliser, mould and smell

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the seven amazon.co.uk listings captured on 19 October 2026. Scores are editorial, not a laboratory test. A missing NPK is a gap, not a zero. The scraped 1:1 field is not the dose for the 250 ml liquid.

  1. RHS, bonsai (retrieved 19 October 2026)
  2. RHS, feeding plants (retrieved 19 October 2026)
  3. Federation of British Bonsai Societies, cultivation (retrieved 19 October 2026)
  4. Federation of British Bonsai Societies, the bonsai year (retrieved 19 October 2026)
  5. Kew, top ten bonsai tips (retrieved 19 October 2026)
  6. Growth Technology, safety data sheets (retrieved 19 October 2026)
  7. Growth Technology, indoor bonsai leaflet (retrieved 19 October 2026)
  8. legislation.gov.uk, retained Regulation (EC) No 2003/2003 Article 9 (retrieved 19 October 2026)
  9. legislation.gov.uk, Fertiliser Regulations 2006 (retrieved 19 October 2026)
  10. ASA ruling, The SEER Centre Trust (retrieved 19 October 2026)