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Seaweed fertiliser or liquid feed, not a full feed

Updated: October 2026

You have Maxicrop 2.5 L on the bench, a tomato crop setting fruit, and a listing that calls both bottles organic. Seaweed fertiliser or liquid feed is the format decision: a biostimulant sits beside a declared feed and does not replace it on hungry crops. The [organic liquid fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/organic-liquid-fertiliser) only shows the role column. This page keeps the stimulant bottles on one side and the tomato and lawn litres on the other. We compared amazon.co.uk listings and public UK sources, and we did not run a laboratory test. A qualifying purchase can earn a commission at no extra cost to you.

You have Maxicrop 2.5 L on the bench, a tomato crop setting fruit, and a listing that calls both bottles organic.

Our top picks

Maxicrop Maxicrop seaweed 2.5 L

Best overall

Maxicrop Maxicrop seaweed 2.5 L
9.2/10about £18.99
View offer
Maxicrop Maxicrop organic tomato 1 L

Alternative

Maxicrop Maxicrop organic tomato 1 L
9.2/10about £11.99
View offer
Maxicrop Maxicrop organic lawn 1 L

Alternative

Maxicrop Maxicrop organic lawn 1 L
8.8/10about £12.19
View offer
On this page
  1. 1.A tonic is not a declared NPK
  2. 2.Maxicrop 2.5 L versus the tomato and lawn litres
  3. 3.The lawn litre is a third job
  4. 4.Iron, title-only tonics, and when to buy both

A tonic is not a declared NPK

The Royal Horticultural Society treats plain seaweed as not a true fertiliser. A biostimulant may sit beside a feed, and it does not treat a deficiency. SBM's Maxicrop note says Original is extract only, below 2 percent of each nutrient, and is not declared as a fertiliser. That is the 2.5 L Soil Association bottle in this set. It is not Maxicrop Natural 5-2-5, which is a different product and is not in this capture. Seven of the nine kept bottles are seaweed stimulants, and they do not print a usable NPK. Naming Ascophyllum nodosum, or a root drench, does not turn the bottle into a tomato analysis. A concrete mix-up: weekly Maxicrop 2.5 L on greenhouse tomatoes after the first truss, with no fruit feed, because the title said organic. The Soil Association mark allows the stimulant in an organic system. It does not supply potassium for fruit. Label checks sit on the organic liquid fertiliser buying guide. A single pick sits on best organic liquid fertiliser.

Maxicrop 2.5 L versus the tomato and lawn litres

Maxicrop 2.5 L is the tonic: Soil Association on the bullet, no NPK, Amazon dilution 1:100, maker label 1:200. The tomato litre names tomatoes, peppers, chillies, aubergines and high potassium. The mixing field reads 4:2:6, and the letters NPK are not printed beside it, so this site does not treat that field as a confirmed analysis. Use the 2.5 L for potting on or a tonic beside a feed. Use the tomato litre when fruit is the job. Use both in the same month on separate days, each at the printed rate. Do not pour a 1:10 Topline cap onto the tomato litre because both bottles are brown.
Maxicrop Maxicrop seaweed 2.5 L

Testsieger

Maxicrop Maxicrop seaweed 2.5 L
9.2/10about £18.99
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The lawn litre is a third job

Maxicrop organic lawn 1 L is for turf every 4-6 weeks at 1:10 or 1:20. It is not a weekly hanging-basket feed, and it is not a substitute for the tomato litre. If the only grass job is a front lawn in June, stay with that bottle. If the only job is pots, leave it on the shelf. How you mix the bottle you already chose sits on how to use organic liquid fertiliser. The argument here is role, not millilitres.

Iron, title-only tonics, and when to buy both

Sunshine 6 L adds chelated iron and names hydroponics. Iron is not a full feed. A greener leaf on a listing bullet is not an NPK. The sample is 4.4 from 8 reviews. Treat that row as seaweed plus iron, not as a tomato substitute and not as a Soil Association bottle. Vitax, Sunshine and Topline can be the tonic side of this split. They cannot stand in for the tomato litre after fruit set. Buy a tonic for mixed pots when you already have a feed. Buy a feed when the greenhouse will not use seaweed. Buy both when you want the Maxicrop 2.5 L mark plus fruit. This page does not rank the nine bottles.

Common questions

Is liquid seaweed a fertiliser?
Plain seaweed is not a true fertiliser on the Royal Horticultural Society wording. Fortified extracts that quote NPK are a different product, and most bottles in this set do not print one. Maxicrop Original is extract only and is not declared as a fertiliser. Treat the brown stimulant as a tonic beside a feed.
Can I skip a tomato feed if I have Maxicrop 2.5 L?
Not after fruit set if the plants are hungry. The 2.5 L is a Soil Association stimulant with no NPK on the listing. The tomato litre is the feed-shaped bottle in this set. You can use both. You should not treat the tonic as a 4-2-6 substitute.
What does Soil Association approval mean on a stimulant?
It means the input may be used in an organic growing system if the directory still lists it. It does not mean the bottle is organic food, and it does not mean it supplies a fruit analysis. Approval is not an efficacy score.
When do I use both in the same month?
When the crop is growing hard and you want the tonic as well as the feed. Keep the rates on each label. Do not add a 1:10 Topline dose on top of the tomato litre in the same can. A separate day is cleaner than one muddy mix.
Is the lawn litre a seaweed tonic?
It is a lawn feed with seaweed, on a 4-6 week interval, not a weekly pot tonic and not a tomato feed. Use it on turf. Leave it if the job is hanging baskets or greenhouse fruit.
Does chelated iron make Sunshine a full feed?
No. Sunshine 6 L is seaweed plus chelated iron. Iron is named. A full NPK is not. It does not replace the tomato litre, and eight reviews are a thin sample.
Why does the tomato field say 4:2:6?
That string is in the amazon.co.uk mixing-ratio field. The highlight says high potassium. The letters NPK are not printed next to 4:2:6. This site does not treat it as a confirmed analysis or as a water ratio.

Related pages

Soil Association organic liquid fertiliser

Organic liquid fertiliser

Best organic liquid fertiliser for a stated UK job

Organic liquid fertiliser buying guide for UK pots

How to use organic liquid fertiliser on this bottle

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 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.

  1. RHS, Seaweed products (retrieved October 2026)
  2. RHS, Biostimulants (retrieved October 2026)
  3. RHS, How to feed plants (retrieved October 2026)
  4. GOV.UK, Manufacturing and marketing fertilisers (retrieved October 2026)
  5. GOV.UK, Organic farming certification (retrieved October 2026)
  6. OF&G, Approved inputs (retrieved October 2026)
  7. SBM, Maxicrop NPK query (retrieved October 2026)
  8. Maxicrop Original label (retrieved October 2026)