Fruit & Vegetable Fertiliser | Organic Plant Food 4-5-6
A balanced 4-5-6 feed for fruit and veg.
from £11.50
Made by Growers · Backed by Science
Organic tomato fertiliser 3-4-6 — 16 organic ingredients, blended for flavour
NPK 3-4-6 16 Organic Ingredients High Potash · K:N 2:1 Slow Release Full Ingredient Transparency Handcrafted in Stockport
Dr Forest Organic Tomato Fertiliser is a slow-release tomato feed with an NPK of 3-4-6, so it carries twice as much potassium as nitrogen. Potassium helps move sugars from the leaves into swelling fruit, and holding nitrogen lower discourages the plant from putting that effort into leaf. It is a dry, milled plant food for tomato plants in pots, grow bags, borders and allotment beds, blended by hand in Stockport from 16 organic ingredients including Yorkshire polyhalite, Scottish seaweed, British biochar and dried worm castings.
A liquid tomato feed goes on every week; one dressing of this keeps working for two to four weeks. Alongside the NPK it brings calcium, magnesium, sulphur and trace elements, while most liquid feeds are mainly N, P and K. The 1.5 kg size comes as two 750 g compostable kraft bags; larger sacks run up to 120 kg.
3-4-6NPK ratio
16Organic ingredients
2:1Potassium to nitrogen
2–4 wkBetween top-dressings
What this formula does for your tomatoes
- Potash-led feeding — potassium at twice the nitrogen, mainly as sulphate from polyhalite and sulphate of potash, with no muriate of potash in the mix
- Colour and aroma — potassium supports lycopene, the red pigment, which with its close relatives breaks down into part of a tomato's aroma
- Calcium in the base — from polyhalite, phosphorous plant meal, basalt and clay, for a steady background supply to developing fruit
- Soil life — biochar gives microbes somewhere to live and worm castings bring them in
- Magnesium from two main sources — a micronised magnesium mineral and polyhalite, for the chlorophyll in every leaf
Dr Forest tomato fertiliser vs a typical liquid tomato feed
Dr Forest Organic Tomato Fertiliser 3-4-6 — dry, slow release
- NPK plus calcium, magnesium, sulphur and trace elements from 16 ingredients
- Biochar and worm castings add soil biology as well as nutrients
- Breaks down over weeks: top-dress every 2–4 weeks
Typical liquid tomato feed — soluble, weekly
- Mainly N, P and K, sometimes magnesium; calcium is rarely in the bottle
- Available at once, and just as quickly washed through by heavy watering
- Adds nothing to soil structure; salts can build up in grow bags over a season
Handcrafted in Stockport
Dr Forest makes premium organic fertilisers in Stockport, Greater Manchester, and this tomato fertiliser is blended by hand in small batches, every ingredient listed individually. The name comes from Joe's grandfather, Dr Forrest, a GP in a Lancashire mining town near Preston who kept a back-garden plot for the runner beans he turned into piccalilli for family and friends. For a straight comparison with the best-known bottles, read what is actually in Tomorite: five tomato feeds compared. Made by Growers. Backed by Science.
What's Inside
All 16 ingredients — what they do and why they are in this tomato feed
This is a multi-input blend, with every ingredient listed individually. The polyhalite is mined 1,200 m below the North Sea off North Yorkshire, the seaweed is hand-harvested in Scottish waters, and the biochar is British and fermented before blending.
01K · Ca · Mg · S
Yorkshire polyhalite — North Yorkshire, slow release
One crystal, four nutrients, all as sulphates: 14% K₂O, 17% CaO and 6% MgO plus sulphur. Unlike conventional potash it releases gradually (Das et al., 2026). More in our polyhalite guide.
0250% K₂O
Sulphate of potash (SOP) — mineral, fast release
The quick potash: 50% K₂O in sulphate form, which covers the start of each feed while the slower ingredients come on stream. No muriate of potash (potassium chloride) is used anywhere in the formula.
0320.9% Mg
Micronised magnesium mineral — mineral, sustained release
Magnesium sits at the centre of every chlorophyll molecule, so it is tied directly to photosynthesis. Ground to 5 microns at 20.9% Mg. Short supply shows as yellowing between the veins of older leaves; see magnesium deficiency in tomato plants.
0412% N
Nitrogen plant extract — plant-derived, controlled release
A plant protein concentrate that soil microbes break down to plant-available nitrogen. Young plants get what they need to establish without a surge of soluble nitrate.
05P₂O₅ · CaO
Phosphorous plant meal — plant-derived, calcined
A calcined plant meal, not rock phosphate, at around 15% P₂O₅ and 9% CaO: phosphorus for rooting after planting out and for flowering and fruit set, plus a second calcium source.
06Slow N
Rapeseed meal — British, slow release
A high-protein seed meal that releases nitrogen steadily over several weeks as microbes break it down. Nitrogen that arrives gradually is less likely to push soft, leafy growth.
07Trace elements
Scottish seaweed meal — hand-harvested, slow release
Dried, milled seaweed bringing zinc, iron, manganese and boron, plus alginates that help compost hold together and hold water.
08Biostimulant
Seaweed extract — British coastal, biostimulant
Included for its biostimulant compounds: seaweed extracts carry growth-active substances such as cytokinins and betaines (Craigie, 2011).
09Triacontanol
Alfalfa meal — plant-derived, slow release
Slow nitrogen and organic matter. Alfalfa meal is also where the growth-promoting substance triacontanol was identified (Ries et al., 1977).
10Carbon scaffold
British biochar — fermented before blending
Stable, porous carbon that stays in the soil for years. Its pores give microbes somewhere to live, and microbial biomass generally rises after biochar goes in, though why is still not well understood (Lehmann et al., 2011).
11Chelation
Humic acid — mineral organic, chelation
Humic substances improve the uptake of some nutrients, nitrate in particular, and help plants acquire iron by holding it in solution (Nardi et al., 2002).
12Biology
Dried worm castings — living biology, available nutrients
Readily available nutrients plus the bacteria and fungi that get the plant meals breaking down.
13Silicon
Silica meal — mineral, structural
Plants short of silicon are often structurally weaker (Epstein, 1999), and a cordon carrying five or six heavy trusses needs a strong stem.
14CEC reservoir
Clay minerals — British, permanent exchange capacity
Montmorillonite and illite clays hold potassium, calcium and magnesium on their surfaces and let them go between waterings, a capacity that does not wear out.
15Trace minerals
Volcanic rock dust (basalt) — mineral, trace elements
A slow trickle of zinc, iron, copper and manganese, which plants need in small amounts to run their enzyme systems.
16Biostimulant
Herbal mixture — plant-derived, biostimulant
Dried plant material added as a varied food source for the soil microbial community.
Where each nutrient comes from
| Nutrient | Main sources | Smaller contributions |
|---|---|---|
| Nitrogen (N) | Nitrogen plant extract, rapeseed meal, alfalfa meal | Seaweed meal, worm castings, herbal mixture |
| Phosphorus (P₂O₅) | Phosphorous plant meal | Nitrogen plant extract, rapeseed and alfalfa meals, worm castings, biochar |
| Potassium (K₂O) | Yorkshire polyhalite, sulphate of potash | Seaweed, alfalfa meal, nitrogen plant extract, worm castings, illite clay, basalt |
| Calcium | Yorkshire polyhalite, phosphorous plant meal | Basalt, clay minerals, seaweed meal, worm castings |
| Magnesium | Micronised magnesium mineral, Yorkshire polyhalite | Seaweed meal, basalt, montmorillonite clay |
| Sulphur | Yorkshire polyhalite, sulphate of potash | Rapeseed meal, seaweed meal |
| Trace elements | Seaweed meal and extract, basalt rock dust | Clay minerals, polyhalite, worm castings |
How to Use
How to use this tomato feed: rates, timing and method
Measuring made simple
This product is a milled powder with a bulk density of 1 g/ml, so grams and millilitres are interchangeable. You can measure by weight on a kitchen scale or by volume using a measuring jug or spoon. 3 level teaspoons = 1 tablespoon ≈ 15 ml. For best results, mix with an equal volume of compost before applying.
Step-by-step: containers and grow bags
- Prepare your potting mix. Measure 5–10 g per litre of compost: 5 g/L for mixes already containing nutrients, 10 g/L for plain or peat-free compost. Mix thoroughly for at least two minutes to prevent localised hot-spots.
- Fill your container and plant. Leave 5 cm headspace for watering. Set the plant at the correct depth and firm gently. If planting into an existing container, mix the fertiliser into the compost before transplanting.
- Water in thoroughly. Water until it runs freely from the drainage holes; this starts the slow-release process. Do not allow the pot to dry completely, because organic nutrient release depends on moisture.
- Wait 10–14 days before the first top-dress. The initial potting mix dose provides nutrition for the first two to three weeks. Begin top-dressing once plants show new growth.
- Top-dress every 2–4 weeks. Apply 1–3 g per litre of pot volume in a band around the outer rim, 10 cm from the stem. Lightly scratch into the top 2–3 cm. Water immediately.
- Adjust to what the plant tells you. Pale, yellowing lower leaves: increase to fortnightly or move toward 3 g/L. Excessively dark green foliage with few flowers: stretch to every 4 weeks and reduce toward 1 g/L.
Application rate table
Containers & pots
| Situation | Rate (g = ml) | Frequency | Notes |
|---|---|---|---|
| Potting mix preparation | 5–10 g per litre of compost | Once at potting | 5 g/L in enriched mixes. 10 g/L in plain or peat-free compost. |
| Container top-dressing | 1–3 g per litre of pot volume | Every 2–4 weeks | 1 g/L for established plants. 2–3 g/L for large containers (20 L+) or peak fruiting. |
Outdoor beds & raised beds
| Situation | Rate (g = ml) | Frequency | Notes |
|---|---|---|---|
| Bed preparation | 150–200 g per m² (up to 250 g for depleted soil) | Once before planting | Fork into the top 10–15 cm. Preparing 2–4 weeks in advance allows nutrients to begin releasing. |
| Outdoor top-dressing | 75–150 g per m² | Every 2–4 weeks | 75 g/m² in fertile soil during vegetative growth. 100–150 g/m² during peak fruiting. |
| Single plant at transplanting | 30–45 g per plant | Once at planting | Mix into the planting hole with an equal volume of soil or compost. 10 cm gap from the stem. |
| Single plant top-dressing | 30–45 g per plant | Every 2–4 weeks | Ring around the plant 10–15 cm from the stem. Lightly scratch in. Water in thoroughly. |
Seasonal feeding guide
| Stage | Timing | Rate & frequency | Goal |
|---|---|---|---|
| Bed preparation / potting mix | 2–4 weeks before planting | Beds: 150–200 g/m². Pots: 5–10 g/L compost | Build a nutrient-rich root zone before the plant arrives |
| Transplant establishment | At planting | 30–45 g per plant into the planting hole | Localised nutrient boost for rapid rooting |
| Early vegetative growth | 10–14 days after transplanting | 75 g/m² or 1 g/L every 3–4 weeks | Healthy structure without excessive nitrogen-driven bulk |
| Active flowering & fruit set | First flowers through heavy fruit load | 100 g/m² or 2 g/L every 2–3 weeks | Potassium and phosphorus support for flower retention and fruit set |
| Peak fruit fill | Heavy green fruit on all trusses | 150 g/m² or 3 g/L every 2 weeks | Maximum demand — sugar loading and lycopene synthesis |
| Ripening & late season | Once fruit begins to colour | Lower range or skip; every 3–4 weeks | Concentrate sugars and volatiles; ease off nitrogen |
Keep the compost moist
Organic nutrient release depends on moisture. Do not allow the pot to dry completely. Water immediately after top-dressing containers, and water single-plant dressings in thoroughly.
Works well combined with…
Use Dr Forest Seaweed Extract Powder as a fortnightly foliar — it adds cytokinins and trace minerals without extra nitrogen. Apply Dr Forest Liquid Gypsum as a root drench if blossom end rot appears mid-season. Use Dr Forest All Purpose Fertiliser 4-4-4 during early vegetative establishment before switching to this formula at first flower.
Growing Guide
Tomato growing guide — varieties, training, watering and feeding by type
Timings are for a typical English season; add a week or two in the north and in Scotland. Our full tomato growing guide goes month by month.
The two growth habits: cordon and bush
Cordon (indeterminate, vine)
- Grows on from one stem until frost or until you pinch out the tip; needs a cane or string and regular side-shooting
- Sets truss after truss, so picking runs for months; most greenhouse varieties are cordons
- Needs feeding right through the season
- UK favourites: Gardener's Delight, Sungold, Moneymaker, Ailsa Craig, San Marzano, Costoluto Fiorentino
Bush (determinate)
- Grows to a set size and crops over three to five weeks; leave the side-shoots on, as each carries a truss
- Suits outdoor beds, patio pots and hanging baskets
- Wants a good feed at planting, then lighter feeding
- UK favourites: Roma, Tumbling Tom, Totem, Red Alert, The Amateur, Maskotka
Semi-determinate varieties
Some paste types reach 90–120 cm, set most of their fruit, then slow right down. Train them as cordons, but feed on the lighter bush schedule once most trusses have set.
Feeding adjustments by variety type
Cherry and cocktail — Sungold, Gardener's Delight, Sweet Million, Tumbling Tom
Naturally sweet. Overfeed a cherry tomato and you get leaf, not fruit.
Standard and medium — Moneymaker, Ailsa Craig, Alicante, Shirley
The classic British greenhouse tomato. Follow the How to Use tab as written.
Beefsteak and large-fruited — Brandywine, Costoluto Fiorentino, Marmande, Coeur de Boeuf
The highest blossom end rot risk, because the blossom end expands fastest. Water evenly, and consider a foliar calcium such as Amino Chelated Calcium while fruit swells.
Plum and paste — San Marzano, Roma, Amish Paste, Giulietta
Dense fruit with a high dry-matter content, which suits a potash-led feed.
Bush — Totem, Red Alert, The Amateur, Maskotka, Tumbling Tom
A strong initial potting mix charge (8–10 g/L), then lighter top-dressing (1–2 g/L). Reduce or stop once most of the fruit has set.
Heritage and heirloom — Brandywine, Black Krim, Green Zebra, Tigerella, Costoluto
Older varieties keep flavour chemistry that modern breeding lost (Tieman et al., 2017).
Greenhouse and polytunnel vs outdoor — what changes
Greenhouse and polytunnel
- Planting from late April, picking into October; 8–12 trusses on a cordon against 4–6 outdoors
- Feed at the upper end of the range and the shorter interval (every 2 weeks at peak)
- Ventilate well and water in the morning; warm, still, humid air suits grey mould
- More blossom end rot risk, because heat drives fast growth and heavy water loss
Outdoors
- Plant out after the last frost: late May in most of England, early June further north
- Choose early or bush varieties: Sungold, Gardener's Delight, Red Alert, Tumbling Tom
- Feed mid-range at the standard interval (every 3–4 weeks)
- Stop cordons at 4–5 trusses and give them the sunniest, most sheltered spot you have
Watering — the make-or-break factor
More tomato problems come from erratic watering than from any shortage of fertiliser. Drought followed by a soaking brings blossom end rot, split fruit and patchy ripening.
01
Containers and grow bags
Water daily in warm weather, twice in a heatwave, until it runs from the base; dry peat-free compost is hard to re-wet. If pots stop taking water, here is why.
02
Raised beds and open ground
Water deeply two or three times a week rather than a little daily, and mulch 5–8 cm deep with compost or straw.
03
Greenhouses and polytunnels
Water at the base in the morning and ventilate afterwards. Drip irrigation on a timer is the most reliable method under cover.
The calcium connection
Calcium travels with water. Ho & White (2005) put blossom end rot down to calcium delivery falling behind demand in the fast-expanding cells at the blossom end, so the calcium in this blend reaches the fruit only if the water does.
Training cordon tomatoes
- Stake or string at planting, before the plant needs it.
- Remove side-shoots weekly, pinching them out at 5–8 cm; check every three or four days in fast growth.
- Stop the plant. Under glass, pinch out the tip after 6–8 trusses, usually late July or early August. Outdoors, stop at 4–5 trusses by early July.
- Remove lower leaves below each picked truss, no more than three at a time.
- Tie in loosely every 20–30 cm with soft twine or clips, never wire.
UK seasonal timeline
| Month | Task | Feeding |
|---|---|---|
| February–March | Sow on a warm windowsill or in a heated propagator at 18–21°C. Do not sow too early. | — |
| April | Pot on into 9 cm pots at the first true leaves; harden off plants going outside; prepare beds and grow bags. | Base charge: 150–200 g/m² or 5–10 g/L |
| May | Plant out: greenhouse late April to early May; outdoors after the last frost, typically late May in most of England. | 30–45 g per planting hole |
| June | First flowers and first truss set, when potassium demand starts to climb. | Begin fortnightly or three-weekly top-dressing |
| July | Peak period. Stop outdoor cordons at 4–5 trusses; greenhouse cordons can go to 6–8. | Every 2 weeks at the upper end of the range |
| August | First ripe fruit. Ease off watering slightly as fruit colours to concentrate sugars. | Reduce to every 3–4 weeks |
| September–October | Pick the rest; green fruit ripens in a drawer with a banana. The biochar stays in the soil for next year. | Lower range or skip; every 3–4 weeks while fruit is still colouring |
Common problems and what to do
Blossom end rot
Water evenly and mulch; in severe cases a root drench of Dr Forest Liquid Gypsum can help. Later trusses usually come good. More in our blossom end rot guide.
Split fruit
The skin cannot stretch fast enough when water floods back in. Water evenly and mulch.
Yellow lower leaves
Interveinal yellowing points to magnesium; this formula has two main magnesium sources, but a foliar spray of Epsom salt (10 g per litre) gives a quick correction. See why tomato leaves turn yellow.
Lots of leaf, few flowers
Feed less often, give six or more hours of sun, and ventilate a greenhouse to keep it under 30°C, above which pollen viability drops sharply.
Blight (Phytophthora infestans)
Plants under glass largely escape it. Outdoors, grow resistant varieties such as Crimson Crush or Mountain Magic, and bin affected foliage. No fertiliser, this one included, protects a plant from blight.
Greenback
Hard green shoulders that never ripen. A potash-led feed covers the potassium side; under glass, leave enough foliage to shade the trusses.
The Science
The science of tomato flavour, and where feeding fits in
A tomato's flavour is the sum of sugars, acids and a large set of volatile compounds you smell rather than taste (Mathieu et al., 2009). Variety matters a great deal: modern commercial varieties carry significantly less of many key flavour chemicals than older heirloom varieties (Tieman et al., 2017), partly because flavour is too genetically complex to breed for easily (Klee & Tieman, 2018).
Why the 3-4-6 ratio works
Potassium's role in moving photoassimilates, the sugars made in the leaves, is one reason it matters for crop quality (Römheld & Kirkby, 2010). In a trial of three potassium levels, tomato lycopene rose in step with potassium supply while yield did not change (Serio et al., 2007). Nitrogen is held back because a tomato given plenty of it grows leaf. The exact 2:1 figure is our formulation choice; the research points that way without fixing a number.
3-4-6NPK ratio
2:1K:N ratio
−13%Fruit nitrate vs chemical feed
+10.8%Lycopene vs chemical feed
Ordinary organic fertilisers vs 100% chemical fertiliser, meta-analysis of 124 studies (Fan et al., 2023): literature figures, not a trial of this product.
Variety sets the ceiling on flavour. Feeding and watering decide how close you get to it.
What makes a tomato taste like a tomato
| Compound | Made from | How |
|---|---|---|
| Sugars (fructose, glucose) | Photosynthesis in the leaves | Carried to the fruit in the phloem, a job potassium supports |
| 6-Methyl-5-hepten-2-one | Lycopene | Oxidative cleavage of lycopene |
| Geranylacetone | Linear carotenoids | Carotenoid cleavage |
| β-Ionone | β-carotene | Carotenoid cleavage |
| Hexanal, (Z)-3-hexenal | Linoleic and linolenic acids | The 13-lipoxygenase pathway |
| 3-Methylbutanal | Leucine, an amino acid | Amino acid breakdown |
Sources: Mathieu et al. (2009); Römheld & Kirkby (2010). The carotenoid-derived compounds are why colour and aroma travel together.
How organic feeding differs from soluble feed — the mechanisms
01
Nitrogen arrives gradually
Organic nitrogen must be broken down by microbes before roots can use it. Across 124 studies, ordinary organic fertilisers cut fruit nitrate by 13.0% and raised fruit sugar by 10.7% against chemical fertiliser alone (Fan et al., 2023).
02
Colour and aroma come from the same place
Lycopene and related carotenoids are broken down in ripening fruit into aroma compounds such as 6-methyl-5-hepten-2-one and geranylacetone (Mathieu et al., 2009). Ordinary organic fertilisers raised lycopene 10.8% against chemical fertiliser (Fan et al., 2023), and in a separate trial lycopene rose with potassium supply (Serio et al., 2007).
03
Calcium depends on water as much as supply
In tomato trials, humid air sent less calcium to the leaves and more to the fruit, a salty root zone cut uptake, and the lowest calcium sat in the tissue where blossom end rot starts (Adams & Ho, 1993). The likely trigger is delivery to fast-expanding cells falling behind demand (Ho & White, 2005).
04
Organic matter builds the soil
Organic fertilisers raised soil organic matter by 24.4% against chemical fertiliser alone, with higher soil nitrogen, phosphorus and potassium (Fan et al., 2023).
05
Biochar gives microbes a home
Its pores give soil microbes somewhere to live, and microbial biomass generally rises after it goes in, though why is still not well understood (Lehmann et al., 2011).
06
Biostimulants act on the plant directly
Humic substances improve nutrient uptake and help plants acquire iron (Nardi et al., 2002). Seaweed extracts carry cytokinins and betaines, and the old view that seaweed works mainly through its nutrients is no longer tenable (Craigie, 2011).
Study data: organic feeding and tomato quality
| Study | Scope | Finding |
|---|---|---|
| Fan et al. (2023) | 124 studies, 2,041 data sets | Ordinary organic fertiliser vs 100% chemical fertiliser: nitrate −13.0%, sugar +10.7%, lycopene +10.8%. All organic types: soil organic matter +24.4% |
| Gao et al. (2023) | 107 papers, 769 data sets | Organic fertiliser vs none: yield +42.2%, lycopene +24.0%, vitamin C +19.0% |
| Serio et al. (2007) | Three potassium levels | Lycopene rose linearly with potassium; yield unchanged |
Scientific references
- Adams, P. & Ho, L.C. (1993). Effects of environment on the uptake and distribution of calcium in tomato and on the incidence of blossom-end rot. Plant and Soil, 154, 127–132.
- Balzergue, C. et al. (2013). High phosphate reduces host ability to develop arbuscular mycorrhizal symbiosis without affecting root calcium spiking responses to the fungus. Frontiers in Plant Science, 4, 426.
- Craigie, J.S. (2011). Seaweed extract stimuli in plant science and agriculture. Journal of Applied Phycology, 23(3), 371–393.
- Das, S. et al. (2026). Polyhalite nutrients driving balanced crop nutrition and sustainable agricultural productivity. Discover Soil, 3, 21.
- Epstein, E. (1999). Silicon. Annual Review of Plant Physiology and Plant Molecular Biology, 50, 641–664.
- Fan, H. et al. (2023). Effects of organic fertilizer supply on soil properties, tomato yield, and fruit quality: a global meta-analysis. Sustainability, 15(3), 2556.
- Gao, F. et al. (2023). Effects of organic fertilizer application on tomato yield and quality: a meta-analysis. Applied Sciences, 13(4), 2184.
- Higo, M. et al. (2020). Impact of phosphorus fertilization on tomato growth and arbuscular mycorrhizal fungal communities. Microorganisms, 8(2), 178.
- Ho, L.C. & White, P.J. (2005). A cellular hypothesis for the induction of blossom-end rot in tomato fruit. Annals of Botany, 95(4), 571–581.
- Klee, H.J. & Tieman, D.M. (2018). The genetics of fruit flavour preferences. Nature Reviews Genetics, 19(6), 347–356.
- Lehmann, J. et al. (2011). Biochar effects on soil biota – a review. Soil Biology and Biochemistry, 43(9), 1812–1836.
- Mathieu, S. et al. (2009). Flavour compounds in tomato fruits: identification of loci and potential pathways affecting volatile composition. Journal of Experimental Botany, 60(1), 325–337.
- Nardi, S. et al. (2002). Physiological effects of humic substances on higher plants. Soil Biology and Biochemistry, 34(11), 1527–1536.
- Ries, S.K. et al. (1977). Triacontanol: a new naturally occurring plant growth regulator. Science, 195(4284), 1339–1341.
- Römheld, V. & Kirkby, E.A. (2010). Research on potassium in agriculture: needs and prospects. Plant and Soil, 335(1), 155–180.
- Serio, F. et al. (2007). Potassium nutrition increases the lycopene content of tomato fruit. Journal of Horticultural Science & Biotechnology, 82(6), 941–945.
- Tieman, D. et al. (2017). A chemical genetic roadmap to improved tomato flavor. Science, 355(6323), 391–394.
Figures describe the published literature on these ingredient classes and are not product-specific yield guarantees.
Questions & Answers
Frequently asked questions about this tomato fertiliser
Before they go in. Mix 5–10 g per litre into the compost for pots and grow bags, or fork 150–200 g per m² into beds 2–4 weeks before planting (up to 250 g for depleted soil). At planting, put 30–45 g into each planting hole, mixed with an equal volume of soil or compost. The first top-dressing goes on 10–14 days after transplanting, once the plant shows new growth.
Every 2–4 weeks, not weekly: every 3–4 weeks in early vegetative growth, every 2–3 weeks from first flowers, every 2 weeks at peak fruit fill, and the lower range or skip, every 3–4 weeks, once fruit begins to colour.
Yes, and it is particularly useful there, because peat-free compost usually starts with lower nutrient levels. Use the higher potting mix rate (8–10 g/L) and begin top-dressing after 7–10 days rather than 14. Combining it with a liquid seaweed foliar spray every 2 weeks gives strong results.
Because a tomato given plenty of nitrogen puts it into leaf, often at the expense of flowers and fruit. The 3% N is enough for healthy foliage without that excess. If plants show nitrogen shortage, apply more frequently within the recommended rates rather than adding a high-nitrogen feed on top.
A North Yorkshire mineral supplying potassium, calcium, magnesium and sulphur in one crystal, as sulphates and without chloride. It releases gradually compared with conventional potash (Das et al., 2026). Our guide to polyhalite vs sulphate of potash compares the two potash sources in this blend.
It covers the supply side, with calcium included to keep a background supply in the root zone. But blossom end rot is mainly a water-supply disorder: calcium reaches the fruit with water, and the rot is thought to start when delivery falls behind (Ho & White, 2005). For severe or recurring cases, supplement with Dr Forest Liquid Gypsum as a root drench every 2–3 weeks once fruit is setting. Remove affected fruit; later trusses usually recover once watering is stabilised.
It works well with them. Use the lower potting rate (5 g/L) initially, apply the inoculant directly to the roots or into the planting hole, and resume normal rates after 3–4 weeks once the fungal networks have formed. The low start is a precaution: high phosphate stopped the partnership forming in laboratory work (Balzergue et al., 2013), though a tomato field trial found no significant effect (Higo et al., 2020). If you need an inoculant, see our Mycorrhizal Fungi Powder.
Yes. Peppers, aubergines and chillies respond well to the same 3-4-6 ratio, and there is a dedicated Chilli & Pepper Fertiliser too. For root veg, brassicas and soft fruit, Dr Forest Fruit & Vegetable Fertiliser 4-5-6 offers a more versatile NPK balance.
Yes. This blend is the slow-release foundation; a liquid seaweed or calcium feed can top up nutrients during peak demand. Avoid replacing the dry base programme with liquid alone.
Yes. Cherry varieties need lighter, less frequent feeding; overfed, they run to leaf. Beefsteaks need the upper end of the range, with extra attention to calcium and even watering, because their large fruit is the most prone to blossom end rot. The Growing Guide tab covers every type.
The biochar gives soil microbes somewhere to live (Lehmann et al., 2011) and the worm castings bring them in. Between them they keep the compost alive enough to break the plant meals down.
Yes. It contains no synthetic chemicals and no toxins that persist in the soil, and there is no withholding period for edible crops. It is safe for pets and children once applied and watered in; keep the bag itself out of their reach.
It is made with organic and natural ingredients: plant meals, mined minerals, seaweed, biochar and worm castings, with no synthetic chemicals and no GMO inputs. We do not hold an organic certification for the blend, so "made with organic ingredients" is the claim we make, and no more.
Cool, dry, out of direct sunlight and sealed between uses; damp wakes the microbes early. It stays effective for at least 18 months. If it clumps, break it up before measuring.
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