The best organic liquid fertilisers, compared.
Top pick: Sunshine seaweed 2.5 L – Highest card score: 5.0 from 5 reviews, scaled to 100, at about £16.99 and a listed 1:200. The file is thin and names no control body. Best value: Maxicrop seaweed 2.5 L – Soil Association named, 4.6 from 3,688 reviews, about £18.99 for 2.5 L. Not the highest star line, and not a declared NPK. Updated October 2026.
Organic liquid fertiliser is a liquid you dilute and apply to pots, beds, a greenhouse crop or a lawn. In the UK it is usually a brown concentrate mixed in a watering can or a sprayer, bought for containers, an allotment or turf through the growing season. A suitable bottle is the job on the label. A multi-purpose seaweed product is a biostimulant. The Royal Horticultural Society treats plain seaweed as not a true fertiliser, so it sits beside a feed and does not replace one when a fruiting crop is hungry. A tomato, pepper, chilli or aubergine bottle should name that crop. A lawn bottle should name turf and how often to apply it. If an inspected plot needs an approved input, the listing should name a UK control body. A title that only says organic is not that mark. Use the dilution on the bottle you hold, because a strong mix and a weak concentrate are different products. Pack fields should agree with the stated volume. The checks are in the [organic liquid fertiliser buying guide](/hub/fertiliser-soil-and-bark-mulch/organic-liquid-fertiliser/sub/organic-liquid-fertiliser-buying-guide).
Organic liquid fertiliser is a liquid you dilute and apply to pots, beds, a greenhouse crop or a lawn.
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Personal buying guide
Question 1 of 2
What are you feeding?
Sunshine seaweed 2.5 L is a seaweed concentrate at about £16.99, listed at 1:200, with a claim of up to 500 litres of made-up feed. Across 5 amazon.co.uk reviews the star line is 5.0, scaled to 100. That is the highest card score in this file, from a thin sample, not a laboratory ranking. Four written reviews in the file are one line each and do not describe a fault or a result. The listing does not mention iron; that sits on the 6 L Sunshine bottle. No control body is named. The top pick is that score, not proof this bottle outperforms Maxicrop seaweed 2.5 L on an allotment.
Pros
Cons
Best for: A smaller garden that wanted 2.5 L of Sunshine seaweed at 1:200 and accepted a five-review sample.
Less suitable: Anyone treating 5.0 from five reviews as a crop rank, or who needed a named certifier.
Specifications
Common questions
How much feed does the listing claim?
A 1:200 dilution, and up to 500 litres from 2.5 L. That arithmetic matches 2.5 times 200. It is a listing claim, not a measured solids test.
Does this bottle add iron?
This listing does not mention iron. The 6 L Sunshine listing does.
Is 5.0 a strong rank?
The listing line is 5.0 from 5 reviews. Four written reviews in the file are one line each and do not describe a fault or a result.
The Topline pack is two 1 L organic-titled seaweed bottles at about £16.99, listed at 1:10, with a United Kingdom origin field. Across 56 amazon.co.uk reviews the star line is 4.8, scaled to 96. The listing says to apply every 7-14 days from March to August on seedlings, plugs and growing plants, and it makes tomato and rose claims without printing an NPK. 1:10 is a much stronger mix than the 1:100 to 1:500 concentrates in this set, so you cannot copy a neighbour's cap onto this pack. No control body is named in the captured bullets. It is a twin-litre stimulant when you will use both bottles in one UK season, not a Soil Association mark or a tomato feed.
Pros
Cons
Best for: A UK season of seedlings and growing plants when you wanted two litres and a printed March-August interval.
Less suitable: Anyone who needed a named certifier, or who would copy a 1:200 cap onto this 1:10 pack.
Specifications
Common questions
How often does the listing say to apply it?
Every 7-14 days from early spring (March) to late summer (August), for seedlings, plugs and growing plants.
Does the listing name a certifier?
The title says organic. No control body is named in the captured bullets. Country of origin is the United Kingdom.
What is the listed dilution?
The mixing-ratio field reads 1:10, which is a much stronger mix than the 1:100 to 1:500 concentrates in this set. Use the bottle label.
Sunshine seaweed 5 L is a seaweed concentrate at about £25.99, listed at 1:200, with lawns and vegetables named on the role line. Across 128 amazon.co.uk reviews the star line is 4.7, scaled to 94. The manufacturer field is Sunshine Renewables UK; the brand field says Generic. The title says organic. The captured bullets do not name the Soil Association, OF&G, or another control body. How you apply it is not stated in the comparison block, so you still have to read the label in the bottle. It is a larger 5 L row when you already accept a title-only organic claim, not a named-body bottle for an inspected plot.
Pros
Cons
Best for: A larger garden that wanted 5 L of seaweed at 1:200 and did not need a named certifier.
Less suitable: Inspected growers, or anyone who needed Soil Association or OF&G on the listing.
Specifications
Common questions
Who makes this 5 L bottle?
The manufacturer field is Sunshine Renewables UK. The brand field is Generic.
Is a control body named?
The title says organic. The captured bullets do not name the Soil Association, OF&G, or another control body.
What dilution is printed?
The mixing-ratio field and the bullet both say 1:200.
Maxicrop seaweed 2.5 L is a Soil Association-named seaweed stimulant at about £18.99, listed at 1:100 for flowers, shrubs, trees, fruit and vegetables. Across 3,688 amazon.co.uk reviews the star line is 4.6, scaled to 92. That is the deepest sample in this set, and still not a laboratory ranking. The listing does not print an NPK. SBM's support note treats Original as below 2 percent of each nutrient and not declared as a fertiliser. A maker label states 45 ml in 9 litres (1:200), so the Amazon 1:100 field and the brand rate stay side by side. Indoor use is asked on the page and not answered in the capture. It is the best value when you wanted a named body and a large UK review file at a mid-shelf price, not a tomato analysis or a 1:10 twin pack.
Pros
Cons
Best for: Mixed pots and allotment beds when you wanted a named Soil Association stimulant and a large review file.
Less suitable: Anyone who needed a tomato analysis, a lawn-only litre, or a single reconciled dilution.
Specifications
Common questions
Which organic body does this listing name?
The bullet says it is approved and certified for organic growing by the Soil Association. The listing does not print an NPK.
What dilution is on the listing?
The mixing-ratio field reads 1:100. The maker label for Original states 45 ml in 9 litres, which is 1:200. Follow the label in the bottle.
Which plants does the listing name?
Flowers, shrubs, trees, fruit and vegetables, in the home, garden or allotment. Indoor use is asked on the page and not answered in the capture.
Shropshire Seaweed 5 L is a cold-pressed Ascophyllum nodosum concentrate at about £40.98, listed at 1:500, with OF&G named on the bullet. Across 1,026 amazon.co.uk reviews the star line is 4.6, scaled to 92. The listing claims up to 2,500 litres of ready-to-use feed from 5 litres, which is 5 times 500 arithmetic, not a measured solids test from this site. Harvest is described as hand-picked from Ireland's Atlantic coast. That is a listing claim. The bullets also say it suits vegan growers and is safe around children and pets as directed. There is no NPK on the listing. It is the species-named, OF&G row when you wanted a high-dilution 5 L, not the cheapest litre on this shelf.
Pros
Cons
Best for: Certified or vegan growers who wanted named Ascophyllum nodosum, OF&G, and a 5 L concentrate.
Less suitable: A first 1 L crop bottle, or anyone buying on shelf price alone.
Specifications
Common questions
What seaweed and process does the listing name?
Ascophyllum nodosum, cold-pressed rather than high-heat alkali extraction. Harvest is described as hand-picked from Ireland's Atlantic coast. That is a listing claim.
Which certifier is named?
The bullet names OF&G in the UK and the USDA in the US. It also says the feed is suitable for vegan growers and safe around children and pets as directed.
How far does 5 L go on the listing?
Dilution is 1:500, and the bullet says the bottle makes up to 2,500 litres of ready-to-use feed. There is no NPK on the listing. The 2,500 litre line is listing arithmetic.
Vitax organic liquid seaweed is priced at about £18.38, with root-drench or foliar-spray wording for flowers, fruit, vegetables, shrubs and trees. Across 541 amazon.co.uk reviews the star line is 4.6, scaled to 92. The title says 1 litre. Number of items is 2 and the liquid-volume field is 2 litres, so check the image and the label before you compare price per litre. The attribute block has no mixing ratio. One United Kingdom review says the rates are on the bottle and are not obvious. No control body is named. Skip it as a pack-size buy until the label in the box matches the title you clicked.
Pros
Cons
Best for: Gardeners who already know the Vitax seaweed rate from a bottle in the shed and will check the pack size on arrival.
Less suitable: Anyone who needed a printed dilution or a settled litre count before buying.
Specifications
Common questions
How do you apply it?
The listing says a liquid root drench or a foliar spray on flowers, fruit, vegetables, shrubs and trees.
What dilution should you use?
The attribute block has no mixing ratio. One United Kingdom review says the rates are on the bottle label and are not obvious. Do not copy another brand's rate onto this listing.
Is the pack one litre or two?
The title says 1 litre. Number of items is 2 and the liquid-volume field is 2 litres. Check the image and the label before you compare price per litre.
Maxicrop organic tomato 1 L is a tomato, pepper, chilli and aubergine feed at about £11.99, with added seaweed extract and a high-potassium highlight. Across 402 amazon.co.uk reviews the star line is 4.6, scaled to 92. The mixing-ratio field reads 4:2:6, which is not a 1:x water recipe. The letters NPK are not printed next to that string, so do not treat it as a confirmed analysis. The bullet names OF&G. The highlight names the Soil Association. Both strings sit in the file without a certificate. A repeated complaint is a spout that holds brown liquid and then leaks and stains. One reviewer linked dark green growth and blossom end rot to too much nitrogen. That is one report, not a trial. It is the fruiting-crop litre when you wanted a feed-shaped bottle, not a general stimulant.
Pros
Cons
Best for: Greenhouse cooks feeding tomatoes, peppers, chillies or aubergines who wanted a 1 L organic-titled crop bottle.
Less suitable: A general tonic for mixed pots, or anyone who needed one settled control-body name and a leak-free spout.
Specifications
Common questions
Is this a general seaweed stimulant?
No. It is a tomato feed with seaweed, and the highlight also names peppers, chillies and aubergines.
What does 4:2:6 mean on this capture?
That string is in the mixing-ratio field. The highlight says high potassium. The letters NPK are not printed next to 4:2:6, so do not treat it as a confirmed analysis.
What do reviewers say about the bottle?
A repeated complaint is a spout that holds brown liquid and then leaks and stains. One reviewer linked dark green growth and blossom end rot to too much nitrogen. That is one report, not a trial.
Maxicrop organic lawn 1 L is a lawn-only liquid at about £12.19, not the all-plants 2.5 L stimulant in this set. Across 98 amazon.co.uk reviews the star line is 4.4, scaled to 88. The listing says every 4-6 weeks in the growing season, and the mixing-ratio field reads 1:10 or 1:20. The bullet names OF&G. The item highlight names the Soil Association. The file contains both strings and does not show a certificate. It suits homes with children and pets as directed. It does not say to walk on wet feed. Use it on turf, not as a weekly pot tonic.
Pros
Cons
Best for: A UK lawn in the growing season when you wanted a 1 L organic-titled liquid on a 4-6 week interval.
Less suitable: Pots, tomatoes, or anyone who needed one settled control-body name.
Specifications
Common questions
Is this the same as the Maxicrop all-plants seaweed?
No. The title and item type are a lawn feed. The all-plants stimulant in this set is the 2.5 L Maxicrop bottle.
Which certifier should you trust on this capture?
The bullet names OF&G. The item highlight names the Soil Association. The file contains both strings and does not show a certificate.
How often is it applied?
Every 4-6 weeks during the growing season. The mixing-ratio field reads 1:10 or 1:20. The bullet says it suits homes with children and pets. It does not say to walk on wet feed.
Sunshine seaweed plus iron 6 L is seaweed plus chelated iron at about £29.99, listed at 1:400, for a watering can or sprayer. Across 8 amazon.co.uk reviews the star line is 4.4, scaled to 88. That is a thin sample, and four United Kingdom reviews sit in the file. One of those texts describes the container spilling when poured. The bullets name vegetables, flowers, lawns, shrubs, houseplants, fruit trees, seedlings and hydroponics. Iron is named. A full NPK is not. Pet safety is asked and not answered in the capture. Skip it if you needed a named control body or a review file deeper than eight ratings.
Pros
Cons
Best for: Gardeners who specifically wanted seaweed plus chelated iron in a 6 L can and accepted a thin sample.
Less suitable: Inspected plots, or anyone who needed a deep review file before buying.
Specifications
Common questions
Is this plain seaweed?
No. A bullet says it is enhanced with chelated iron for chlorophyll and greener foliage, as well as seaweed extract. A full NPK is not printed.
Where can you use it, according to the listing?
Vegetables, flowers, lawns, shrubs, houseplants, fruit trees, seedlings and hydroponics, by watering can or sprayer. Pet safety is asked and not answered in the capture.
How many reviews support the 4.4 score?
The listing line is 4.4 from 8 reviews. Four United Kingdom reviews are in the file, and one describes the container spilling when poured.
Nine amazon.co.uk listings were read from the stored pages and the UK notes already on file. There is no laboratory test. The score on each card is the amazon.co.uk star rating scaled to 100. The top pick is the highest of those scores: Sunshine seaweed 2.5 L at 5.0 from 5 reviews. That file is thin, and the score is not a crop trial. The best value is a separate award in the same product file: Maxicrop seaweed 2.5 L, the Soil Association-named stimulant with the deepest review file, at a mid-shelf price. It does not also hold the top score. A 5.0 from five reviews is not treated as proof of a better allotment result than 4.6 from 3,688. The weights below are the reading checklist. They sum to 100. They are not a second total that moves the badges.
Star line on the card
40%The amazon.co.uk star rating scaled to 100. Sunshine seaweed 2.5 L at 5.0 is the top of this block. The scaled figure is the card score and the top-pick assignment. It is not a measured yield.
Role and dilution
25%A readable job, a dilution or a stated clash, and volume fields that agree. A 1:10 bottle is not scored as if it were a 1:500 concentrate. A missing mixing ratio, or a 4:2:6 field that is not an NPK, is recorded as printed.
Named control body
20%Soil Association or OF&G named on the listing. A title that only says organic scores nothing here. Two Maxicrop litres name both bodies in different fields, with no certificate in the file, so that clash stays visible.
Review-file depth
15%The count behind the star line. Maxicrop seaweed 2.5 L at 3,688 leads this block. Five reviews and eight reviews add little weight beside a 4.6 from hundreds or thousands. One written complaint is not a trial.
Match the job, the control body and the dilution before you match the star line. Prices below are the stored amazon.co.uk snapshot, not a live re-check. This is not a laboratory test.
Organic liquid fertiliser on amazon.co.uk, in the bottles kept for this comparison, is almost always a brown seaweed concentrate you dilute in a watering can. Six listings are multi-purpose seaweed stimulants. One adds chelated iron. One is a lawn liquid. One is a tomato liquid with a high-potassium highlight. The Royal Horticultural Society treats plain seaweed as not a true fertiliser. A biostimulant sits beside a feed and does not replace it on a hungry crop.
Listed ratios run from 1:10 to 1:500. Maxicrop seaweed 2.5 L is 1:100 on Amazon and 1:200 on the maker label. Follow the label in the bottle you hold.
Sunshine, Topline and Vitax say organic and do not name a control body in the captured bullets. Soil Association and OF&G are named only where the listing actually names them.
Sunshine seaweed 2.5 L is 5.0 from 5 reviews. Maxicrop seaweed 2.5 L is 4.6 from 3,688. The higher star line is the top-pick score. It is not evidence of a larger crop.
Name the job first. Mixed pots and transplant shock want a seaweed stimulant. Fruiting tomatoes, peppers, chillies and aubergines want the tomato litre, which carries a high-potassium highlight and a mixing field of 4:2:6 that is not printed as NPK. A lawn wants the lawn litre every 4-6 weeks at 1:10 or 1:20. Chelated iron is named only on the 6 L bottle. If you are inspected, the listing should name a UK control body. GOV.UK says food sold as organic needs one.
Use the rate on the bottle you hold. Topline is listed at 1:10. Maxicrop seaweed 2.5 L is 1:100 on the amazon field and 45 ml in 9 litres (1:200) on the maker label. Sunshine 5 L and Sunshine 2.5 L are 1:200. The iron bottle is 1:400. Shropshire is 1:500, and the claim of up to 2,500 litres is 5 times 500, not a solids test. Vitax has no mixing ratio in the attributes, and the title says 1 litre while the item and volume fields say 2 litres.
Three typical situations, each with a recommendation from this comparison.
You want a brown seaweed stimulant for mixed pots and beds. Maxicrop seaweed 2.5 L is the best value at about £18.99, with the Soil Association named and 4.6 from 3,688 reviews. The amazon field says 1:100. The maker label for Original says 45 ml in 9 litres (1:200). It is not a declared NPK feed.
You need a control body an inspector can see, or vegan-grower wording, on a large concentrate. Shropshire Seaweed 5 L names OF&G and cold-pressed Ascophyllum nodosum, listed at 1:500, at about £40.98. It is 4.6 from 1,026 reviews. The 2,500 litre claim is listing arithmetic, not a solids test.
After fruit set you want a crop bottle, not only a stimulant. Maxicrop organic tomato 1 L is about £11.99, with 4.6 from 402 reviews, and the highlight names tomatoes, peppers, chillies and aubergines. The mixing field reads 4:2:6 without the letters NPK. Reviewers report a leaking spout. A lawn is a different litre.
The top pick is Sunshine seaweed 2.5 L at about £16.99. It has the highest card score because amazon.co.uk shows 5.0 from 5 reviews, scaled to 100, with a listed dilution of 1:200. That sample is five reviews, four of them one line, and no control body is named. The best value is Maxicrop seaweed 2.5 L at about £18.99: Soil Association on the bullet, 4.6 from 3,688 reviews, and a mid-shelf 2.5 L. It is a stimulant, not a declared NPK, and the amazon 1:100 field does not match the maker's 1:200 label. Shropshire Seaweed 5 L is the OF&G, species-named concentrate. The tomato litre and the lawn litre are separate jobs. None of these scores is a laboratory test.
Sunshine seaweed 2.5 L
Highest card score: 5.0 from 5 reviews, scaled to 100, at about £16.99 and a listed 1:200. The file is thin and names no control body.
Maxicrop seaweed 2.5 L
Soil Association named, 4.6 from 3,688 reviews, about £18.99 for 2.5 L. Not the highest star line, and not a declared NPK.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the nine stored amazon.co.uk listings. A title that says organic is not a control-body certificate. The 4:2:6 tomato field is not an analysis from this site. Shropshire's 2,500 litre line and Sunshine's 500 litre line are listing arithmetic. A 5.0 from five reviews is not a crop trial.
Expert source (DIY & tools): Lee Burkhill (Garden Ninja) (external profile) – public expert commentary used as a research source, not as a contributor to our pages.
This page contains affiliate links to amazon.co.uk (tag pcuk26-21). If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are from the listings. This is not a laboratory test.
