Tomorite vs Dr Forest: five tomato feeds compared
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Tomato feeding
Tomorite vs Dr Forest: five tomato feeds compared
By Joe, Founder of Dr Forest · May 2026
I make one of the five feeds compared here. What each one actually does, and what each is for.
Five UK tomato feeds often searched together. If you're looking for a Tomorite alternative, or trying to work out what Tomorite actually contains (NPK, calcium, nitrogen, potash), this covers the ground.
Tomorite vs Dr Forest anchors the comparison; three organic-certified liquid alternatives sit alongside it.
The five:
- Tomorite (Levington / ICL): NPK 4-3-8 liquid, seaweed-enriched, market-leading mineral feed.
- Tomorite Organic: NPK 3-3-3 liquid, certified organic, vegan, peat free.
- RocketGro Tomato Food: NPK 3-1-5 liquid, Soil Association organic and Vegan Society certified, digestate base.
- Envii Maximato: NPK 4-2-6 liquid, certified organic and vegan, alfalfa base with added calcium and magnesium.
- Dr Forest Tomato 3-4-6: NPK 3-4-6 slow-release granular, made with organic ingredients, UK-made in Stockport, tuned for quality, flavour and aroma.
Two distinctions run through them. Format: four liquid concentrates, one slow-release granular. Purpose: mineral for yield, organic for flavour and quality.
What you're looking for in a tomato feed is a nitrogen-to-potassium ratio of 1:2 (nitrogen at half of potassium). That's what peer-reviewed research finds optimal for fruit set, sugar loading and eating quality in tomatoes: Fallah et al. (2021) on the N:K ratio itself, Ho (1996) on potassium's central role in fruit sugar accumulation and firmness. Combined with adequate calcium against blossom-end rot, that's the technical spec a purpose-built tomato feed is aiming at.
Only two of these five hit that 1:2 target. Tomorite classic (mineral 4-3-8) at N:K = 4:8. Dr Forest 3-4-6 (granular, calcium built in) at N:K = 3:6. Both land exactly on 1:2. The other three carry tomato branding, but their NPK is largely what their organic input delivers rather than a design choice: digestate arrives at 3-1-5, an alfalfa base at 4-2-6, a balanced plant extract at 3-3-3. All three are competent organic feeds working with what nature provides. It's an organic-liquid limitation as much as anything, not intent. Perhaps the exception is RocketGro, who sell the same 3-1-5 NPK as their Lawn Feed and general Plant Fuel. A proper lawn feed should run higher nitrogen and lower potassium than a tomato feed (grass wants nitrogen for leaf growth). Selling one 3-1-5 digestate under multiple application labels is a rebranding pattern rather than formulation to task. Not an attack: I use their organic potting mix myself. Just an accurate reading of the label. Only a mineral concentrate (which can be dosed to any ratio) or a multi-input granular blend (which can combine sources to hit a target) is free of the underlying organic-liquid constraint.
In short
Precisely tuned for tomato fruiting:
Cheap mineral concentrate: Tomorite classic (4-3-8).
Slow-release granular, calcium-rich, tuned for quality, flavour and aroma: Dr Forest 3-4-6 (K:N 2:1). UK-made, science-backed.
Organic liquids working with what nature provides:
Balanced plant-extract liquid under the Tomorite brand: Tomorite Organic (3-3-3).
British certified-organic digestate liquid: RocketGro (3-1-5).
Alfalfa-based liquid, calcium and magnesium named: Envii Maximato (4-2-6).
Meet the five products
Product one · The classic
Tomorite
Around since the 1950s. High-potash mineral concentrate, NPK 4-3-8, enriched with seaweed extract, magnesium and named trace elements (iron, manganese, boron, copper, zinc). 20ml in 4.5 litres of water; 1L bottle makes ~225L. Not organic. Not vegan.
Best for: weekly fruiting-stage feeding at the lowest cost per feed on the shelf.
Product two · The organic version
Tomorite Organic
Separate product, same brand. Liquid, NPK 3-3-3 with magnesium, certified organic, vegan, peat free, Nordic seaweed. The "up to 50% more yield" claim applies against unfed plants, not against the classic. Note: 3-3-3 is a generic all-purpose NPK ratio, not the high-potash fruiting profile the Tomorite name is known for.
Best for: a certified-organic vegan liquid in the familiar watering-can routine. 3-3-3 trades peak potash for the certification.
Product three · The digestate liquid
RocketGro Tomato Food
Liquid, NPK 3-1-5. Soil Association organic and Vegan Society certified. Built on digestate: the residue left when crops (rye, maize, grass from their Somerset farm) are broken down to produce biogas. Contains "secondary minerals and trace elements" (not named). 1.5L makes 75 watering cans. The 3-1-5 profile lands on a workable 2:1 K:N ratio for fruiting; RocketGro sell the same NPK as their Lawn Feed and as a general Plant Fuel, so it's a generic organic digestate sold as a tomato feed rather than one designed for tomatoes.
Best for: a British peat-free liquid at organic certification if you don't mind the digestate smell. Ventilate when mixing.
Product four · The high-potash organic
Envii Maximato
Liquid, NPK 4-2-6. Certified organic and vegan-friendly. Alfalfa-based, Ascophyllum nodosum seaweed from the Irish Atlantic, added calcium, magnesium, and named trace elements (iron, boron, copper, manganese, zinc, molybdenum). 1L makes 250L, applied every 7–14 days from flowering. Note: 4% nitrogen is at the high end for a tomato feed at fruiting, largely a function of the nitrogen-rich alfalfa base.
Best for: greenhouse growers wanting the highest potash of the organic liquids, with explicit calcium and magnesium.
Product five · Ours
Dr Forest Tomato 3-4-6
Slow-release powder, NPK 3-4-6, blended in small batches in Stockport. Made with organic ingredients (finished blend isn't certified). Sixteen inputs including Yorkshire polyhalite, Scottish seaweed, fermented biochar, humic and fulvic acid, and insect frass. 2:1 K:N ratio at 6:3, with roughly 3 parts calcium : 1 part magnesium : 3 parts potassium (Ca:Mg:K) to keep all nutrients in balance, grounded in peer-reviewed soil-science research. Runs a touch dusty on application because of the finely milled mineral inputs. Simple workaround: put the fertiliser and an equal amount of compost in a bucket, put the lid on and shake to mix. Applied that way, no dust.
Best for: quality, flavour and aroma over raw yield. UK-made, science-backed. 4% phosphorus and 6% potash tuned for fruit-stage sugar and firmness, with calcium built in.
The format question
Most guides skip this bit.
Tomorite, Tomorite Organic, RocketGro and Envii are all liquid concentrates: dilute, water in, repeat weekly. The plant takes what it can before the next watering rinses the rest through the soil.
Dr Forest 3-4-6 is a slow-release granular powder. Worked into the compost or topsoil, broken down by soil biology over weeks, released as the plant calls for it. One application lasts a fortnight or more.
Liquid feeds give week-to-week control. Step doses up or down as the plant looks. The trade-off is you have to be there with a watering can every week.
Slow-release granular builds in slack. Apply, walk away for a fortnight, come back to a plant that's still being fed. Less week-to-week precision, more resilience.
Greenhouse with the grower in daily: any of the liquids works. Outdoor garden with weather and weekends away: a slow-release base does most of the work.
NPK head-to-head
Figure 1 · Stated NPK by product
Five tomato feeds, side by side on paper NPK
Manufacturer-stated N, P (as P₂O₅) and K (as K₂O), in percentage by weight. Source: product labels.
None is high-nitrogen. Tomorite classic and Envii both give 4% N; the others sit at 3%. Tomatoes don't need heavy nitrogen during fruiting: it pushes leafy growth at the expense of fruit.
The potash spread is wide. Tomorite classic leads at 8%, Dr Forest 3-4-6 and Envii both sit at 6%, RocketGro at 5%, Tomorite Organic lowest at 3%. Paper NPK is one signal among several: a 4-3-8 liquid releases everything inside a watering and needs reapplying; a 3-4-6 slow-release feeds at the lower number across a fortnight, giving a flatter curve that better tracks demand.
Calcium is missing from Tomorite, Tomorite Organic and RocketGro. Envii Maximato lists it. Dr Forest includes it from rock phosphate and gypsum. Calcium deficiency causes most of the blossom-end rot seen in greenhouse and outdoor tomatoes.
Mineral or organic: what each optimises for
Behind the NPK sits the deeper choice. Are you feeding for yield, or for flavour and quality?
Mineral fertilisers like Tomorite classic are tuned for yield. Synthetic NPK in plant-available form drives fast growth and heavy fruiting. The yield is real and reproducible, which is why commercial glasshouses use mineral feeds at scale.
Organic fertilisers are tuned for flavour and quality. They release gradually through soil biology, deliver a broader nutritional picture (calcium, trace elements, biostimulant fractions), and build soil structure across seasons. The trade-off is typically 10–20% lower yield per plant in the short term.
What you get instead is fruit that tastes of something. A 2024 study in Nature Scientific Reports (Li et al.) found all 21 starch and sucrose metabolism genes in tomato fruit upregulated under organic fertilisation versus mineral-only controls: the genes responsible for sugar accumulation. Combined with high potash driving firmness and brix (Ho 1996), that's the flavour profile growers chase.
Tomorite classic optimises for kilograms. Envii Maximato has the highest paper NPK among the organic options. RocketGro's 3-1-5 and Tomorite Organic's 3-3-3 are certified organic but neither heavily fruiting-tuned. Our 3-4-6 optimises for what the kilograms taste of. A commercial grower selling by weight goes mineral. A kitchen gardener growing for the table goes organic, ideally an organic blend tuned for tomato fruiting.
Worth naming a real constraint on the organic liquid category: you get what nature gives you. The NPK of a liquid organic feed is broadly whatever its input source delivers. You can adjust concentration, but you can't redesign the ratio without changing the input. RocketGro's 3-1-5 lands on a workable 2:1 K:N for fruiting, but the same digestate NPK is sold as their Lawn Feed and general Plant Fuel too, so it's a generic organic profile sold as a tomato feed rather than one designed for tomatoes. Envii Maximato's 4-2-6 is largely the alfalfa profile, and 4% nitrogen is at the high end of what tomatoes want at fruiting. Tomorite Organic's 3-3-3 is a generic all-purpose NPK ratio. The high potash people expect from the Tomorite name lives in the classic 4-3-8; this product is just balanced NPK sold under the same brand. None are precisely tuned for tomato fruiting the way Tomorite classic's mineral 4-3-8 can be. A slow-release granular blend like Dr Forest 3-4-6 can approach that precision by combining multiple inputs to hit target ratios, which is a structural advantage of the granular format over liquid.
For the fuller argument on why the mineral-versus-organic choice depends on what you're optimising for, see Organic vs chemical tomato fertiliser.
Feed the plant, not the packet
If you're picking a feed for flavour, make sure you're growing a variety prized for it. A flavour-focused feed won't turn a Moneymaker into a Sungold. There's a ceiling written into the genetics, and you can't feed past it. If eating quality is the reason you're growing your own, the variety choice matters more than the feed choice.
Five UK-grown varieties known for flavour, worth the greenhouse or allotment space:
- Sungold (cherry, F1). RHS Award of Garden Merit. Brix around 9. Orange, small, intensely sweet with a hint of tropical citrus. Consistently wins blind taste tests against every other cherry. Cordon, thin-skinned, best under glass.
- Sweet Aperitif (cherry). Sugar-acid balance sharper than Sungold, more complex, refreshing. Long trusses, heavy yields, greenhouse or sheltered outdoors.
- Gardeners' Delight (cherry). RHS AGM. Sweet-tangy, reliable, forgiving. The UK classic for a reason. Suits both heated and unheated greenhouses.
- Ailsa Craig (salad). Scottish heritage variety. Medium red fruits with well-balanced tomato flavour. The traditional British salad tomato that Moneymaker isn't.
- Costoluto Fiorentino (beefsteak). Italian heirloom with deeply ribbed 200–350g fruits. Extraordinary depth of flavour, particularly for sauces. Needs warmth: heated greenhouse or a very sheltered spot.
If you're growing any of these, an organic feed tuned for quality has something to work with. If you're growing Moneymaker or Alicante for reliable heavy crops, honestly, Tomorite classic will get you where you want to go at the lowest cost, and no fancier feed will make those varieties taste like a Sungold. Match the tool to the job.
For the fuller argument on choosing feed by growing goal, see Best fertiliser for tomatoes: an honest guide.
Ingredients and ethics
Tomorite classic: synthetic mineral concentrate plus seaweed extract, magnesium, five named trace elements. Not organic, not certified vegan. Does what it says on the bottle.
Tomorite Organic: same brand, organic-certified inputs, vegan and peat free, seaweed carries across. The certification is the reason to pick it over the classic.
RocketGro: digestate base (crops broken down by microorganisms into biogas). Soil Association organic and Vegan Society certified. The digestate explains the smell reviewers mention.
Envii Maximato: alfalfa base with Irish Atlantic seaweed, added calcium, magnesium and a named list of trace elements. Certified organic and vegan-friendly.
Dr Forest 3-4-6: fifteen-plus named inputs including Yorkshire polyhalite, sulphate of potash, calcined plant meals, Scottish seaweed, fermented biochar, humic and fulvic acid, and insect frass. 2:1 K:N at 6:3 and roughly 3:1:3 Ca:Mg:K to keep all nutrients in balance, grounded in peer-reviewed soil-science research. UK-blended in small batches in Stockport. Made with organic ingredients; the finished blend isn't certified-organic.
What each label actually declares
What's printed on the bottle or bag varies more than you'd expect. UK and EU fertiliser regulation requires a bulk NPK declaration; individual ingredients only have to be named above certain thresholds. Most liquid feeds sit below those.
| What's declared | Tomorite | Tomorite Organic | RocketGro | Envii Maximato | Dr Forest 3-4-6 |
|---|---|---|---|---|---|
| Bulk NPK | 4-3-8 | 3-3-3 | 3-1-5 | 4-2-6 | 3-4-6 |
| Magnesium | Yes | Yes | Yes | Yes (named) | Yes (named) |
| Calcium | Not listed | Not listed | Not listed | Yes (named) | Yes (rock phosphate, gypsum) |
| Trace elements | Fe, Mn, B, Cu, Zn | "Via seaweed" | "Secondary minerals" | Fe, B, Cu, Mn, Zn, Mo | Named, multi-source |
| Seaweed enrichment | Yes (origin unstated) | Yes (Nordic) | No | Yes (Irish Atlantic) | Yes (Scottish) |
| Source compounds | Not declared | Not declared | Digestate stated as base | Alfalfa stated as base | All declared by name |
| Named inputs (approx) | ~6 | ~3 | ~2 | ~10 | 15+ |
Tomorite classic: brown, odourless, pH 6. Mineral-salt fingerprint. The SDS (Dec 2021) doesn't name source compounds; the mixture doesn't hit REACH disclosure thresholds.
Tomorite Organic: brown, characteristic-odoured, pH 4.1. Plant-extract fingerprint (likely vinasse, molasses or similar). The actual input isn't named on label or SDS.
RocketGro: names its base as digestate from Somerset-farm crops. Trace elements grouped as "secondary minerals". The smell matches digestate chemistry.
Envii Maximato: names an alfalfa base, Ascophyllum nodosum seaweed, and a list of trace elements. More ingredient detail on the label than the other three liquids.
Dr Forest 3-4-6: every input named on the bag, fifteen-plus.
Nobody's hiding anything wrong. All five are formulated and sold legally, and each disclosure level is normal for its category. But if you want to know what's going into your soil, the five labels give you very different amounts of information.
Cost per gram of nutrient
| Product | Pack | Price | Cost per gram NPK | Cost per gram NPK+Ca+Mg | Cost per week |
|---|---|---|---|---|---|
| Tomorite classic | 1L | £9 | ~5p | ~5p† | ~8p |
| Dr Forest 3-4-6 | 1.5kg | £11.50 | ~6p | ~3p | ~10-15p |
| RocketGro Tomato Food | 1.5L | £10 | ~7p | ~7p† | ~3p |
| Envii Maximato | 1L | £11 | ~8p | ~7p† | ~9p |
| Tomorite Organic | 1L | £12 | ~11p | ~10p† | ~8p |
Dr Forest 3-4-6 is the only product on the page that publishes both calcium (7%) and magnesium (2.25%) percentages, which makes the NPK+Ca+Mg figure directly calculable. The four values marked † are estimates based on typical formulations. Cost per week assumes one tomato in a 20L pot in mid-season: Dr Forest at the label rate for active flowering (2g per litre of pot volume every 2-3 weeks, so 40g every 2-3 weeks for a 20L pot), giving a band of ~10p per week at the three-week end to ~15p at the two-week end. Liquid feeds at manufacturer's dilution across 2L of feed water per plant per week.
For the mathematicians: you'll notice Dr Forest delivers more NPK per week than the liquid feeds (roughly 2 to 6 times more, depending which liquid you compare against). That's the nature of slow-release organic granulars. What isn't taken up immediately doesn't get wasted; it binds to soil organic matter and feeds soil microbes, building a nutrient reserve that releases gradually over the season. Feeding the microbes as well as the plant (which liquids mostly can't do, being water-soluble even in organic form) builds beneficial microbe populations and soil health. It's part of why dry organic fertilisers often improve yields over successive seasons: the substrate itself gets better.
That reserve is also what makes organic feeding more forgiving. Go on holiday for a fortnight, and a plant fed on a granular has been drawing steadily from soil reserves the whole time. A plant on weekly liquids is closer to a knife edge: miss a feed and it starts running short within days. The same buffer is why organic-fed plants tend to show fewer nutrient deficiencies through the season: soil reserves smooth the highs and lows of nutrient availability.
Founder's note
Full disclosure: I make one of the five products on this page. This is my honest opinion, not one-sided marketing dressed up as helpful content. If I couldn't use my own product, of the four alternatives here I'd pick Envii Maximato. The named calcium and magnesium against blossom-end rot, the alfalfa-and-seaweed base, and the highest potash of the certified-organic liquids all stack up. Two caveats. First, the 4% nitrogen is at the high end for tomatoes at fruiting. When flowering starts I'd cut the dose by roughly 25%. Second, at that point I'd supplement with a small dose of mineral sulphate of potash to bump the potassium closer to where the plant wants it. That gives you an organic-liquid base with a targeted mineral top-up.
Which one's right for you
The heaviest fruit per plant at the lowest cost per feed. Weekly liquid routine. Standard supermarket-tomato results, just bigger and faster. If yield is the metric, this is the answer.
A certified-organic vegan liquid with the strongest fruiting-stage numbers among the organic options, plus explicit calcium and magnesium against blossom-end rot. NPK 4-2-6.
A British peat-free liquid at organic certification, digestate base. NPK 3-1-5. Distinctive earthy digestate aroma; open outdoors when mixing.
Certified-organic and vegan inputs in a recognised garden-centre brand. Yield lower than the classic; NPK 3-3-3 is balanced rather than fruiting-focused. Pick for the certification and the shelf presence.
Tomatoes that taste like tomatoes, with the sugars, acids and aromatics organic feeding builds. Yield a touch lower than the classic; eating quality is the trade. Slow-release, less work.
At-a-glance comparison
| Factor | Tomorite | Tomorite Organic | RocketGro | Envii Maximato | Dr Forest 3-4-6 |
|---|---|---|---|---|---|
| Best for | Maximum yield | Familiar organic brand | British digestate liquid | Highest-potash organic liquid | Flavour and quality |
| Format | Liquid | Liquid | Liquid | Liquid | Slow-release powder |
| NPK | 4-3-8 | 3-3-3 | 3-1-5 | 4-2-6 | 3-4-6 |
| Calcium | Not listed | Not listed | Not listed | Yes | Yes |
| Seaweed | Yes | Nordic | None | Irish Atlantic | Scottish |
| Certified organic | No | Yes | Yes (Soil Association) | Yes | Made with organic ingredients |
| Vegan | No | Yes | Yes (Vegan Society) | Yes | Plant-based, insect frass |
| Peat free | Not stated | Yes | Yes | Not stated | Yes |
| Application | Weekly | Weekly | Weekly | Every 7–14 days | Every 2–3 weeks |
| Made in | UK (industrial) | UK (industrial) | Somerset farm | UK | Stockport, small-batch |
Mineral feeds drive yield. Organic feeds drive flavour and quality. Two valid choices, depending on what you want to eat at the end of the season.
There isn't a winner. There's a fit. Two are precisely tuned for tomato fruiting: Tomorite classic (cheap mineral, highest yield) and Dr Forest 3-4-6 (organic granular, calcium-rich, UK-made, science-backed, tuned for quality, flavour and aroma). Three carry the NPK profile of their organic input rather than a designed target ratio, working within the organic-liquid constraint: Envii Maximato (4-2-6 alfalfa with named Ca and Mg), RocketGro (3-1-5 digestate), Tomorite Organic (3-3-3 balanced plant extract). All three are competent organic feeds. Buy whichever fits what you want at the end of the season.
The Dr Forest tomato range
Slow-release, multi-input, plant-based. Made in small batches in Stockport.
- Premium Tomato Fertiliser 3-4-6The fruiting-stage feed compared above. NPK 3-4-6, calcium-rich, slow-release.
- Premium Fruit & Vegetable Fertiliser 4-5-6If you grow more than tomatoes. Same multi-input approach, broader balance for mixed beds.
- Brix+ liquid biostimulantA weekly liquid top-up if you want both formats running at once.
Working out how much to buy? Read the wider organic-vs-chemical comparison or our guide to diagnosing yellow tomato leaves.
Frequently asked questions
Is Tomorite high in nitrogen?
No. Tomorite is a high-potash feed, not a high-nitrogen one. The classic Tomorite formulation is NPK 4-3-8, meaning the potash level is twice the nitrogen level. Tomato plants don't need heavy nitrogen during fruiting because too much nitrogen pushes leafy growth at the expense of fruit. Most tomato feeds, including Dr Forest 3-4-6, are deliberately low-nitrogen and high-potash for this reason.
Is Tomorite high in potassium?
Yes. Tomorite classic leads the five feeds compared here at 8% potassium (the K in NPK 4-3-8), the highest of any UK garden-centre tomato feed. Potassium drives flavour, fruit firmness and disease resistance in tomatoes. Tomorite Organic sits much lower at 3% because it's a balanced 3-3-3 rather than a fruiting-tuned formulation. Dr Forest 3-4-6 and Envii Maximato both sit at 6%; RocketGro at 5%.
Does Tomorite contain calcium?
No. Neither Tomorite (the classic) nor Tomorite Organic list calcium on the label. The classic Tomorite Safety Data Sheet doesn't declare individual source compounds; the mixture doesn't hit REACH disclosure thresholds. Calcium deficiency is the cause of most blossom-end rot in outdoor and greenhouse tomatoes, which is why some organic tomato feeds (Envii Maximato and Dr Forest 3-4-6 among the five here) add named calcium to guard against it. RocketGro also doesn't list calcium.
What is Tomorite's NPK?
The standard Tomorite Concentrated Tomato Food is NPK 4-3-8 in the UK formulation. The newer Tomorite Organic Concentrated Tomato Food is NPK 3-3-3. The two are sold as separate products with different formulations, not as alternative branding for the same feed.
Is Tomorite organic?
The classic Tomorite is not organic. Tomorite Organic, which is a separate product from the same brand, is certified organic and vegan, with peat-free production. If you're searching for an organic version, look specifically for the word "Organic" on the label, not just the Tomorite name.
Is Tomorite Organic the same as Tomorite?
No. They share the brand name and the seaweed-enriched concentrate format, but the formulations are different. The classic is NPK 4-3-8 and not organic. The organic version is NPK 3-3-3 with magnesium, certified organic and vegan, peat-free. The two suit different growers and different priorities.
Can I use Dr Forest as a Tomorite alternative?
You can use Dr Forest 3-4-6 instead of Tomorite, but it's not a direct replacement. Tomorite is a weekly liquid feed; Dr Forest 3-4-6 is a slow-release granular feed applied every two to three weeks. The feeding routine is different, the nutritional picture is broader, and the per-plant seasonal cost is higher. If you want a like-for-like Tomorite replacement in liquid format, our liquid range is closer in workflow. If you want a one-and-walk-away alternative to weekly dosing, the 3-4-6 powder does that.
Is liquid or slow-release granular better for tomatoes?
Neither is better in the abstract. A liquid feed gives you week-by-week control and is harder to forget. A slow-release granular feed delivers nutrients gradually over weeks, builds soil structure over time, and survives a couple of weeks of holiday neglect. In a controlled greenhouse run by an attentive grower, liquid programmes work well. In an outdoor garden with weather and weekends away, slow-release feeds do more of the work for you.
Are organic tomato feeds better than mineral ones?
It depends on what you're optimising for. Mineral feeds are tuned for yield: faster nutrient release, heavier fruit per plant, lower cost per feed. Organic feeds are tuned for flavour and quality: a broader nutritional picture, slower release that builds soil over time, and better-tasting fruit. A 2024 study in Nature Scientific Reports (Li et al.) found that all 21 sugar and starch metabolism genes in tomato fruit were upregulated under organic fertilisation compared with mineral-only controls. Those are the genes responsible for sweetness and aroma. The trade-off is typically a 10–20% lower yield in the short term. If you want the heaviest crop, choose mineral. If you want the best-eating tomatoes, choose organic, and ideally an organic blend with high potash like Dr Forest 3-4-6.
Which is the best organic tomato fertiliser in the UK?
Worth naming first: of the four organic tomato feeds on this page, only Dr Forest 3-4-6 hits the peer-reviewed N:K target of 1:2 for tomato fruiting (3:6, calcium built in). Tomorite Organic, RocketGro and Envii Maximato carry the NPK profile of their organic input source rather than a designed target ratio. All three are competent organic feeds; the constraint is structural, not intent. Organic liquids can't fully redesign a nutrient ratio without changing the input. Tomorite Organic: mainstream shelf presence, NPK 3-3-3, balanced plant extract. RocketGro: British certified-organic digestate at NPK 3-1-5, high potash. Envii Maximato: highest potash of the certified-organic liquids at NPK 4-2-6 alfalfa base, with named calcium and magnesium against blossom-end rot. Dr Forest 3-4-6: slow-release, sixteen named inputs, calcium built in, UK-made, tuned for quality, flavour and aroma. Full disclosure from the founder: if I couldn't use my own product I'd pick Envii Maximato, cut the dose by 25% at flowering, and supplement with a small dose of sulphate of potash.
Which offers the best value per gram of nutrient?
Per gram of NPK: Tomorite classic is cheapest at ~5p, the mineral advantage. Dr Forest 3-4-6 is second at ~6p, closer to the mineral than to the other organic products. RocketGro sits at ~7p, Envii Maximato at ~8p, Tomorite Organic at ~11p. Per gram of NPK+Ca+Mg: Dr Forest 3-4-6 moves to first at ~3p because it's the only product on the page publishing both calcium (7%) and magnesium (2.25%) percentages. Weekly cost for one tomato in a 20L pot in mid-season: RocketGro ~3p, Tomorite classic and Tomorite Organic ~8p, Envii Maximato ~9p, Dr Forest 3-4-6 ~10-15p at the label rate for active flowering (2g per litre every 2-3 weeks). Estimates for the four products that don't publish full Ca and Mg percentages assume typical formulations.
Sources
- Levington Tomorite product label and manufacturer data, NPK 4-3-8 with magnesium and trace elements. Available via major UK retailers (Tesco, Amazon UK, B&Q).
- Levington Tomorite Organic Concentrated Tomato Food, NPK 3-3-3 with magnesium, certified organic, vegan, peat free. Manufacturer data available via specialist garden retailers.
- Dr Forest Premium Tomato Fertiliser, NPK 3-4-6. Product page at drforest.co.uk/products/organic-tomato-fertiliser.
- RHS (Royal Horticultural Society). Tomatoes: outdoor and greenhouse. Guidance on feeding frequency and timing through the fruiting period.
- Levington Tomorite Concentrated Tomato Food Safety Data Sheet (Evergreen Garden Care UK Ltd), revision date 14 December 2021. Confirms brown liquid, pH 6, no individual ingredients declared under REACH Annex II.
- Tomorite Organic Concentrated Plant Food Safety Data Sheet (Evergreen Garden Care UK Ltd), issue date 7 June 2021. Confirms brown liquid, pH 4.14, characteristic odour, no individual ingredients declared under REACH Annex II.
- RocketGro Tomato Food product information (RocketGro Ltd), 1.5L liquid concentrate, NPK 3-1-5, Soil Association organic and Vegan Society certified, made from anaerobic-digestion crop digestate. Product page: rocketgro.co.uk/product/tomato-food.
- Envii Maximato product information (Envii Ltd), 500ml and 1L liquid concentrate, NPK 4-2-6, certified organic and vegan, alfalfa-and-seaweed base with added calcium and magnesium. Product page: envii.co.uk/products/maximato.
- Ho, L.C. (1996). The mechanism of assimilate partitioning and carbohydrate compartmentation in fruit in relation to the quality and yield of tomato. Journal of Experimental Botany, 47(Special_Issue), 1239–1243. On potassium's role in tomato fruit quality and brix.
- Li et al. (2024). Comparative transcriptomic analysis of tomato fruit under organic vs mineral fertilisation regimes. Nature Scientific Reports. On the upregulation of sugar and starch metabolism gene expression under organic feeding.
- Fallah, M., Delshad, M. & Sheikhi, H. (2021). The effects of cluster pruning and the K:N ratio on greenhouse tomato yield and quality. Horticulture, Environment, and Biotechnology 62: 691–700. DOI: 10.1007/s13580-021-00358-7. On the 1:2 nitrogen-to-potassium ratio as optimal for tomato fruit set, sugar loading and eating quality.
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