Dr Forest
Organic Living Soil Fertiliser
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Organic Living Soil Fertiliser
A two-part veg and bloom feed with a phosphorus charge worked in once. Amend the soil, feed with water, reuse it for years.
Dr Forest living soil fertiliser is a complete two-part organic feeding programme — a nitrogen-led Veg blend, a potash-led Bloom blend, and a slow phosphorus charge worked into the soil once. It runs on a single principle: phosphorus belongs in the soil as a bank, not in every feed. Amend the soil once, top-dress the two blends by the week, and grow on water alone.
It is built for larger pots and beds — the grower filling a fabric bed or a run of big containers who wants one soil that lasts, not a shelf of bottles. One living soil for the whole plot — tomatoes, chillies and courgettes, roses and dahlias, vegetables, fruit and flowers alike. Handcrafted in small batches in Stockport, made with organic ingredients, plant-based charge available.
The easiest way to grow
Charge the soil once, scatter a scoop of feed by the week, finish on plain water. No bottle of the week, no measuring jugs, no EC to chase, no runoff to pour away — and the same soil comes back next year. If you can top-dress and water, you can run it.
Why the phosphorus is separate
Phosphorus is slow and it banks in the soil for years, so it only needs applying once. Put it in every feed and you over-apply it — and excess phosphorus buys no extra flower or fruit. It locks out zinc and iron and runs off into water. Keeping it as a one-time charge is what lets you re-feed nitrogen, potash, calcium and magnesium all season without ever stacking phosphorus.
Reusing your soil? This is the whole point
Blends at full strength, and only a third of the phosphorus charge — last year's phosphorus is still banked. Top the organic matter back up with compost and you are away. You bought the soil once; you do not buy it again.
★★★★★ 5-star across all platforms · 4,300+ reviews. Compostable packaging. Handcrafted in Stockport, Greater Manchester.
Veg blend — 3.5-0.4-2.8
Thirteen inputs, nitrogen-led, on a carbon backbone of organic alfalfa meal and bokashi-fermented bran. Calcium and magnesium are available from day one; humic and fulvic acid at 1% each carry the biology.
Analysis
N 3.5% · P₂O₅ 0.4% · K₂O 2.8% · CaO 2.9% · MgO 1.9% · SO₃ 8.1%
Alfalfa meal · amino-acid nitrogen from molasses extract · zeolite · gypsum · bokashi bran · seaweed meal · kieserite · malted barley · sulphate of potash · biochar · humic acid · fulvic acid · boron complexed with humic acid.
Bloom blend — 1.9-0.4-3.6
Nitrogen drops back; potash and calcium rise. The nitrogen is deliberately lean — in flowering and fruiting, high nitrogen grows leaf at the expense of flavour, aroma and fruit set. Lean nitrogen is the single most effective thing you can do for eating quality.
Analysis
N 1.9% · P₂O₅ 0.4% · K₂O 3.6% · CaO 3.7% · MgO 1.7% · SO₃ 10.0%
Alfalfa meal · zeolite · gypsum · bokashi bran · seaweed meal · amino-acid nitrogen from molasses extract · kieserite · malted barley · sulphate of potash · biochar · humic acid · fulvic acid · boron complexed with humic acid.
Why neither blend carries much phosphorus
Because phosphorus does not belong in a feed. It is slow, it banks for years, and it only needs applying once. Bundle it into every scoop and it over-applies — and excess phosphorus gives no extra yield or quality, it locks out zinc and iron and runs off. Keeping it separate is what lets you cut it to a third on reused soil while everything else carries on at full strength.
The phosphorus charge — choose one
Finely ground and steamed. A biological apatite, so soil acid and biology break it down readily. The more reliable of the two: faster, less fussy about pH, forgiving if your soil drifts. It carries a little nitrogen of its own — the 3.5 — which nudges a build gently towards yield. Animal-derived, so not for a plant-based soil.
The plant-based choice, and nitrogen-free — so it holds the flower at its leanest, the flavour build. Ground fine so soil biology and root acids can weather it. Slower than bone meal and more dependent on an acidic soil, so hold the pH near 6.2 and pair it with mycorrhizal fungi.
Both charges are worked in once and banked for the whole season. Rock phosphate is the plant-based, nitrogen-free choice for the leanest flavour build; bone meal is the reliable all-rounder that adds a little nitrogen of its own.
How to feed
Work the charge in once, then top-dress the blends weekly and water as normal. Weekly dressing meters the feed out steadily rather than dumping it — it ramps potash smoothly into flowering and holds magnesium level.
Step one — the charge, 1 week before planting
Bone meal 9g per litre of soil, or rock phosphate 12g per litre. Mixed through the soil once, a week before you plant. It has no nitrogen, so there is no burn risk and you can plant straight into it.
Growing phase — Veg blend, weekly
Around 1.4g per litre of soil each week through the growing phase, top-dressed and watered in.
Flowering and fruiting — Bloom blend, weekly
Around 1.3g per litre of soil each week through flowering. Switch from Veg to Bloom when the first flowers set.
The finish
Plain water for the last two to three weeks. Demand falls and nitrogen tapers — the ripening that lifts flavour and aroma.
Three strengths — same blends
How much for your soil
| Soil volume | Charge (bone / rock) | Veg (season) | Bloom (season) |
|---|---|---|---|
| 80 litres | 720g / 960g | ~450g | ~640g |
| 120 litres | 1,080g / 1,440g | ~670g | ~960g |
| 200 litres | 1,800g / 2,400g | ~1,120g | ~1,600g |
| 300 litres | 2,700g / 3,600g | ~1,680g | ~2,400g |
| 400 litres | 3,600g / 4,800g | ~2,240g | ~3,200g |
| 500 litres | 4,500g / 6,000g | ~2,800g | ~4,000g |
Standard (Balanced) build. On reused soil, take a third of the charge and leave the blends as they are.
Get the pH right or none of it works
Aim for 6.2 to 6.5. Slightly acidic soil is what dissolves the phosphorus charge — above about 6.8 the release slows sharply, and no amount of extra phosphorus fixes a pH problem. On rock phosphate, aim for 6.2 and check mid-cycle: it leans on soil acid more than bone meal and carries a little carbonate that nudges pH the wrong way.
Pairs well with
A living soil mycorrhizal fungi powder at planting (near-essential on rock phosphate), humic acid to carry the cation load, and a compost or worm-castings base to hold magnesium through flowering. The base mix is not a bystander — it carries the reserve the whole programme draws on.
Running low mid-season? Restock any part from the Living Soil Refills. New to it? See how to top-dress like a pro and what mycorrhizal fungi do.
The formula is set against the measured nutrient optima for flowering and fruiting crops, not tradition. Three ideas do the work: keep phosphorus low and banked, keep flowering nitrogen lean, and let the soil buffer the rest.
What the feed delivers — and what your plants need
Every level is set against peer-reviewed trials on flowering and fruiting crops, not tradition. Here is what a standard build puts into the soil solution, against what the plant actually wants — and the one that matters most is phosphorus.
| Nutrient | This feed delivers | Flowering plants need | Fruiting & root veg need |
|---|---|---|---|
| Nitrogen | high in veg, lean through flower | low in flower — lifts flavour | moderate and steady |
| Phosphorus | ~27 mg/L, from the charge | 25–30 mg/L | 35–50 mg/L — add extra P |
| Potassium | ~160 mg/L | 60–175 mg/L | ~300 mg/L — add extra K |
| Calcium | high, from day one | to sufficiency | high |
| Magnesium | ~55 mg/L | 35–70 mg/L | 35–70 mg/L |
"But don't flowers need a phosphorus spike?"
It is the most common belief in growing, and the peer-reviewed answer is no. A flowering plant's phosphorus demand is real but modest, and the same 25–30 mg/L in the soil solution covers every stage — bloom included. Raise it above that and flower number and weight do not move (Westmoreland & Bugbee 2022; Shiponi & Bernstein 2021). A "PK spike for bloom" sells feed; it does not grow more flower. Bloom boosters seem to work only because they also cut the nitrogen — and it is the lower nitrogen doing the work, not the phosphorus. Dr Forest gets that effect honestly: nitrogen steps down in the Bloom blend while the charge holds phosphorus flat at the level the flower actually uses.
How much phosphorus you feed — Dr Forest vs the rest
Every other living-soil feed bundles phosphorus into the amendment and re-adds it each grow. This is the phosphorus in the feed itself, from each product's own published analysis.
| Living-soil feed | P₂O₅ in the feed | How it is applied |
|---|---|---|
| Dr Forest Veg & Bloom | 0.4% | a separate one-time charge |
| Leading grow-stage feeds | 3% | in the feed, re-added every grow |
| Craft bloom blends | 5% | in the feed |
| High-phosphorus bloom feeds | 8% | in the feed, every grow |
Some of these use the same micronised rock phosphate Dr Forest does — they simply bundle it into a 3–8% feed and re-apply it every stage, every crop. Dr Forest works it in once as a separate charge and takes only a third on reused soil, so the soil never loads up.
Why re-amending a 3–8% phosphorus feed goes wrong
Rock phosphate and bone meal are slow-release — they weather over years, not weeks. A feed carrying 3–8% phosphorus doses that slow mineral at a rate that would only make sense for a fast inorganic salt the plant uses up each cycle. But slow phosphorus does not leave. Re-amend every grow and you add it far faster than the plant can take it up, so it climbs.
A plant draws about 25–30 mg/L of phosphorus from the soil solution and no more. Above that there is no gain in growth, flower or fruit (Westmoreland & Bugbee 2022) — everything past sufficiency simply accumulates.
High soil phosphorus blocks the uptake of zinc and iron, the two micronutrients behind a clean finish and behind aroma and flavour. The plant can look fed and still run short of them.
Slow phosphorus added early and topped up each cycle sits at its highest late in the grow and into the next — exactly when you want the feed easing off for a clean ripening. You cannot turn a banked mineral back down.
In controlled trials, raising phosphorus above sufficiency does not lift yield or quality. It raises tissue phosphorus, micronutrient lock-out and leaching instead (Westmoreland & Bugbee 2022; Shiponi & Bernstein 2021).
Why phosphorus does not belong in the feed
Put a slow phosphorus into the feed and top-dress it cycle after cycle, and it stacks in the soil far faster than the plant can draw it down.
Either way, you pay for it
In a living soil the phosphorus stays put. Bundled into an all-in-one feed, you cannot turn it down without starving the nitrogen and potash the plant still needs — so on a reused soil it only ever climbs, when all you actually needed to replace was nitrogen and potassium. The soil gets harder to run each year, not easier.
In a soluble mineral feed the phosphorus you do not need just washes out — expensive run-off, and a pollution problem, for no benefit to the plant.
Dr Forest keeps phosphorus in a one-time charge instead: top up nitrogen and potassium by the week, and the banked phosphorus holds steady at what the plant actually uses.
Dr Forest keeps it separate — so the soil lasts
Phosphorus lives in a one-time charge, worked in once and never fed again. On a second or third grow you take just a third of the charge — because last year's is still banked — while nitrogen, potash, calcium and magnesium carry on at full strength. Phosphorus stays flat at the ~27 mg/L the plant actually needs, the soil never loads up, and it finishes clean grow after grow. Our bloom feed carries 0.4% phosphate; a typical "bloom" amendment carries 5–8%.
Why the charge goes in a week before planting
Phosphorus is slow, so you add it before the plant needs it — not when it needs it. Worked into the soil at planting, it has the whole veg phase to weather, and it is ready and waiting the moment bloom demand climbs. Add the same slow phosphorus at the flip instead and it is barely started — still locked in the mineral through the weeks the plant wants it most, and only catching up long after flowering has peaked.
Max yield — how weight is won, and what it costs
Nitrogen, not phosphorus, is the real lever on both weight and flavour — and the two pull in opposite directions. Held lean through flower, nitrogen sends the plant's energy into aroma, flavour and potency; pushed up, it grows more bulk at the expense of those compounds (Saloner & Bernstein 2021). That trade is the whole reason there are three builds.
The peer-reviewed route to more weight is a longer vegetative phase — a bigger frame with more flowering sites — carried on higher nitrogen. Max yield does exactly that, and nothing else.
More vegetative time builds a larger plant with more sites to flower. Most of the extra weight comes from here, and it costs nothing in quality — only time.
Flower nitrogen is lifted toward the ~160–190 mg/L that maximises weight in the trials (Saloner & Bernstein 2021). This is the trade: the same nitrogen that adds bulk dilutes aroma and potency.
The extra nitrogen comes from a mid-flower grow-N top-up, not from cranking the whole blend. Push the blend and you drag potassium past its ceiling (toxicity, no gain) and magnesium past the point it starts costing biomass — so only the nitrogen moves.
More phosphorus adds no weight — it is already at sufficiency. Max yield runs the same charge as every other build; the weight is won on nitrogen and frame, not on feeding more P.
The bone meal charge and a gentle start
Max yield pairs with the bone meal charge, which carries a little nitrogen of its own. It releases slowly, as protein, so at planting the soil holds only about 40–60 mg/L nitrogen — gentle, ideal for settling a young plant, and without the salt burn a soluble feed would risk. It builds into the vegetative range over the first few weeks, just as the growing frame wants it. Going for pure flavour, or planting the tenderest seedlings? The rock phosphate charge is nitrogen-free.
Calcium, magnesium and potassium — sufficiency, not ratio-chasing
The blends sit on a calcium-first base with magnesium and potassium held in a sensible band (roughly a 3:1:3 Ca:Mg:K aim). The old Albrecht "ideal ratio" theory has been tested and does not hold — yield responds to each nutrient clearing its own sufficiency floor, not to a fixed ratio (Kopittke & Menzies, 2007). So the programme feeds to sufficiency and no further, which is also what keeps salt and leaching down.
Why dry organic beats liquid synthetic
Organic amendment raised soil organic carbon 12.9% over mineral-only fertiliser, and 20.6% under no-dig (Allam et al., 2022).
Across 537 experiments, organic inputs raised biomass 56% while raising plant diversity; inorganic-only raised it 42% and reduced it (Shi et al., 2024, Nature Communications).
Ascophyllum seaweed feeds the soil biology and, in foliar and soil trials, tends to raise soluble sugars, vitamin C and the sugar-to-acid ratio — the flavour compounds, not just the weight.
Kopittke & Menzies (2007), Soil Sci. Soc. Am. J. 71:259 — sufficiency over ratio. · Allam et al. (2022) — soil organic carbon. · Shi et al. (2024), Nature Communications — 537-experiment meta-analysis. · McGinnis (2023), NDSU — bloom-booster myth. Optima drawn from the peer-reviewed flowering-crop nutrition literature (Bugbee, Utah State; Bernstein, Volcani; Zheng, Guelph).
Dr Forest — Made by Growers. Backed by Science.
Handcrafted in Stockport, Greater Manchester. Named after Joe's grandfather Dr Forrest, a GP near Preston who kept a back-garden plot for the runner beans he turned into piccalilli.
Everything you need to run the programme, step by step:
Feeding calculator · Feeding schedule · Phosphorus & flavour: the science